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Antenna Design | Coaxial Cable | Antenna (Radio)
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Nida and Poloy who through their examples taught me how to be responsible. To them I give my deepest respect.. Mimi. strong and steadfast for what one aspires for.DEDICATION This book is sincerely dedicated to the memories of Ricardo.. They died but their ideals will survive. 4 .
...................................... 6 7 15 26 36 48 60 75 85 99 105 116 131 139 151 158 162 169 172 175 186 194 196 200 5 ............. QUAD LOOP ANTENNA Model QA-2F........ 5/8 WAVE ANTENNA Model WD-2.......................................................................... APPENDIX............................................. FORMULAS FOR CONVERTING ANTENNA DESIGNS FOR OTHER FREQUENCY BANDS............... COLLINEAR ANTENNA Model SD-22............ ANSWERS TO REVIEW QUESTIONS............. GROUNDPLANE ANTENNA Model FQ-2................... GROUNDPLANE ANTENNA Model FC-2.... BIBLIOGRAPHY..........TABLE OF CONTENTS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 INTRODUCTION.................. DISCONE ANTENNA Model CD-2P.............................................................................................................................................................................. GLOSSARY OF ANTENNA TERMS....................................................... COAXIAL DIPOLE Model Cd-2............................. DISCONE ANTENNA Model CD-2T.............................................. MULTI-ELEMENT YAGI-UDA ANTENNA ARRAY.... 5/8 WAVE ANTENNA Model WA-2........... J-FED HALFWAVE ANTENNA Model JF-2. STACKING YAGI ANTENNAS...................................... DIPOLE ANTENNA (gamma fed) Model DP-2F................................................................................ GROUNDPLANE ANTENNA Model FA-2................................................. YAGI-UDA ANTENNA Model YG-23.................. STACKED DIPOLE ARRAY Model SD-24..................................... 5/8 WAVE ANTENNA Model PF-2C. DISCONE ANTENNA Model CD-2W..................
A highly detailed no-guessing antenna dimensions for other frequency bands are described in other books in this series written by the author. Obviously a knowledge in operating a VHF transceiver is the most important. much of the signal (almost half) is lost in the cable and will substantially degrade your antenna's performance. ruggedness. The approach applied in this book is similar to the do-it-yourself methods of trade books and theories are kept to a minimum. weight. However. 6 . wind loading and availability of materials must be taken into account to realize an optimum performance from a particular antenna. use the larger RG-8/U cable instead. Detailed illustrations are extensively used throughout the whole process of antenna construction to simplify the otherwise difficult to comprehend technical jargon. certain factors like portability. signal gain versus size. In selecting a design. The choice of a certain design for a particular application is left to the decision of the constructor. making a pig tail. compactness. More than this length. If it is unavoidable to extend this length. It is the author's hope that this book will provide adequate information to anyone wishing to build his own antennas for VHF tranceivers. this is the only way you can avoid signal losses in the cable. the formulas for conversion give only a generalized information and much of the fine-tuning of the new dimensions is left to the actual experimentation of the constructor. Although this cable is about four times more expensive than RG-58/U cable. Here is one rule of a thumb in installing VHF antennas: If you use an RG-58/U coaxial cable to feed the antenna. The author assumes that the interested constructor has already some experience in basic construction techniques related to radiocommunications equipment installation like soldering VHF connectors to coaxial cables. do not use more than 20 meters or 60 feet long. The antenna designs presented here are specifically cut to the dimensions necessary for proper operation in 140-150 MHz VHF band. Each chapter deals with a particular design and an extra chapter at the last part is added to help the constructor in converting the given antenna dimensions for other frequencies. cutting aluminum tubes and using an SWR meter.INTRODUCTION This book is one of a series designed to help anyone who wants to construct antennas for radio transceivers but who has only a basic knowledge in radiocommunications technology.
If you are situated in the center of a town or a city. This is accomplished by the groundplane radials which are usually made of thin metal rods or tubes each cut to quarterwavelength long and mounted at the base of the antenna. Generally. An artificial ground must then be used since the antenna is well above the ground in this case. The rods sometimes bend downward at an angle of about 45 degrees below the horizontal. The radiation pattern of the transmitted signal is extremely important since it must be transmitted and received in densely populated areas as well as over long distances. some means must be provided to simulate this artificial ground. 7 . This is not a problem in automobiles since this artificial ground is provided by either the metal roof or body of the car. antennas for VHF bands are mounted as high off the ground as practical to overcome the limitations of the so called line-of-sight transmission and reception. Omnipattern is also the best choice when you do not know the exact direction or location of the station you are communicating with. antennas with directive patterns are more complex in design and will be discussed in later chapters. Directive pattern is practical only if you know exactly which direction must the signal be beamed to. omnidirectional pattern is best suited for you. in order to maximize the transfer of RF energy. However. This angle is important to maintain the correct impedance match of the system.1 GROUNDPLANE ANTENNA Model FA-2 Reliable communications in radio systems depends upon the over-all effectiveness of both the base station and mobile unit antennas. For tower installations however.
the brass rod for acetylene welding is recommended SO-239 VHF female connector without flange Stove bolts . The operational frequency bandwidth of FA-2 is from 140 MHz up to 150 MHz exhibiting an SWR response of less than 1.5:1 over the entire bandwidth.inside diameter 8 .The ease of construction and low cost of a groundplane antenna makes it an ideal choice for VHF operators. The groundplane radials are made of cheaper aluminum tubes. Obviously.brass.stainless or GI Hex nuts .brass or stainless Lockwashers . The unit described in this chapter uses bronze rods for the radiating element because of their availability and a bronze rod is the easiest to connect to the center pin of the coaxial connector.1 Groundplane antenna Model FA-2. It has a gain of 1 dB (unity gain) compared to a real dipole. Figure 1. Its signal pattern is omni-directional.brass. stainless or GI Aluminum plate gauge 14 or 16 U-bolts with accompanying hex nuts and lockwashers 1/8'' x 3/4'' 1/8'' id 1/8'' id 2'' x 6'' Dimensions 3/8 id x 20'' each 1/8'' diameter 1 8 8 8 1 2 *id . Materials List Quantity 4 1 Specification/Description Aluminum Tubes Brass Rod . the antenna is not easy to disassemble once completed so its use is commonly confined to fixed installations requiring little maintenance.
It is made from a 1/8'' thick aluminum plate cut to 2'' x 6''. Drill a hole in the plate big enough for the SO-239 VHF connector to insert into (about 5/8'' or 15. Figure 1.3 for the proper dimensions. Next drill four holes at the other end of the plate following Figure 1. Drill the hole at the point about 1" away from one end (see Figure 1.2). Make sure that the distance between one pair of holes perpendicular to the length of the metal sheet must be the same with the distance of both ends of the U-bolt that will be inserted into it. Figure 1.8 mm).2 Antenna mount and hole Dimensions.3 Hole dimensions for the U-bolts. 9 .Construction First of all construct the antenna mount.
4 Hole dimensions for the radial elements around large hole. Figure 1.4 for the proper dimensions.5 Bending the aluminum mounting plate. Figure 1. drill eight holes (1/8" diameter) around the large hole following Figure 1. Bend the aluminum plate down to a 90° angle (see Figure 1.Next. 10 . Follow the illustration for the exact point to bend.5).
7). Figure 1. Cut the brass rod to a length of 19" (48.7 Preparing one end of the brass rod to fit inside the SO-239.Insert the SO-239 VHF connector facing downwards into the mounting plate and fix it permanently with its nut (see Figure 1. The brass rod may or may not fit into the center pin immediately.26 cm) and insert one of its end into the center pin of the SO-239 connector (see Figure 1.6).6 Mounting the SO-239 into the plate. 11 . Discard the grounding ring/lug. Figure 1. so you may need to file away a small portion at the end of the rod to reduce it to a smaller diameter.
9 Bending the tubes.9). Figure 1.8). 12 . Figure 1. The direction of the bend must be parallel with the axis of the drilled hole (see Figure 1.Cut four aluminum tubes to a length of 20" each and drill two holes (1/8 " diameter) at one end (see Figure 1.8 Preparing the tubes. Bend the aluminum tubes to a 45 degree angle at the point 1 inch away for the end with two holes.
13 .10).Mount the four aluminum tubes into the angled plate by bolting each element with 1/8" x 3/4" stove bolts (see Figure 1. brass or GI.10 Mounting the tubes on the metal plate. The stove bolts must be made of rust resistant material such as stainless steel. Figure 1.
11 Mounting the antenna to the mast. 14 . you can mount the antenna to the mast using the two U-bolts .Finally . Figure 1.
A slight bend or kink in the elements has no negative effects on the performance of the antenna. This particular version of the groundplane was evolved in an emergency situation where there were very few tools available. The total size of the antenna is much reduced when disassembled and becomes convenient to carry in transport. Experience has proven its reliability in the rugged life of mobile operations. This unit features quick-detach elements to facilitate for easy and fast disassembly of the antenna. The antenna elements are made of durable bronze materials so it can survive the stresses caused by the regular mounting and dismounting of the antenna. then this design is recommended.2 GROUNDPLANE ANTENNA Model FQ-2 The antenna model FQ-2 is a development from the basic configuration of a groundplane. so a groundplane design was created which did not require drilling of holes. Assembly or disassembly takes only a couple of minutes. The electrical characteristics of this antenna are the same with those of model FA-2. The place was aboard a fishing boat and there was no drilling tool around. just straighten it and it is again functional. It is so durable that you have to intentionally cut it to pieces to destroy it. If you have accidentally bent an element. If you plan to use a groundplane in mobile operations. The only difference between the two models is the mechanical construction and type of materials used. It is also a lot easier and faster to construct compared to the FA-2 design. It can be easily inserted inside your backpack while you are travelling. 15 .
Materials List Quantity 5 Specification/Description Brass rods .the brass rod used for acetylene welding is recommended PL-259 VHF male connectors PL-258 VHF straight connector Aluminum plate gauge 14 or 16 U-bolts with accompanying hex nuts and lockwashers Plain washer GI or stainless steel short length of coaxial cable 2" long 2" x 6" Dimensions 1/8" diameter 2 1 1 2 1 1 Construction Reduce one end of a brass rod to a smaller diameter enough to be inserted into the center pin of the PL-259 connector. File also a notch at its end as shown in Figure 2. Insert the rod into the PL-259 and solder it to the center pin (see Figure 2.1c).1b. Figure 2. 16 . File away any excess solder that is bulging out of the center pin.2 Preparing the end of a brass rod and soldering it to PL-259.
Figure 2. Figure 2.4 Inserting the vinyl insulator into the PL-259.3 Trimming the rod to its proper length. Insert the vinyl jacket into the rod all the way inside the PL-259 (see Figure 2.26 cm) following Figure 2.3. Cut a small piece of coaxial cable (about 2 inches) and remove its inner conductor and braid (shield). 17 . Cut any protruding portion of the jacket. You will only need the vinyl outer jacket.After soldering the rod into the PL-259 cut it to a length of 19" (48.4). The vinyl jacket serves as an insulator between the brass radiator rod and the body of PL-259.
The diameter of the eyehook form must be dimensioned in such a way that the straight connector can be easily inserted into or pulled out of it. Bend one end of each brass rod to an eyehook shape as shown in the following illustration (Figure 2. The epoxy glue must cover the gap between the rod and the PL-259 to avoid the seepage of rainwater inside the connector. 18 . Figure 2.6). (Figure 2.5).5 Sealing the gap with epoxy glue. Next prepare the radial elements. Figure 2.Prepare a small amount of epoxy glue and place it over the protruding portion of the vinyl insulator.6 Shaping one end of the brass rods to an eyehook form.
Figure 2. 19 . measure 19 inches from the point where the rod starts to bend into the eyehook form. bend the brass rods to a 45 degree angle (see Figure 2. The direction of the bend must be perpendicular to the plane of the eyehook end. Next.8 Bending the brass radial rod. Bend the rods at the point 1-1/4 inches away from the center of the eyehook form.7). Mark the measured point at the other end and cut the brass rod at this point (see Figure 2.7 Trimming the radial rod to its proper length.After bending one end of all four brass rods into the necessary shape. Figure 2.8).
Figure 2.9 Connecting the coaxial cable to the PL-259.Solder the RG-58/U coaxial cable to the remaining PL-259 following the illustrated steps (see Figures 2. 20 .9 and Figure 2. Ü Figure 2.10 Assembling the PL-259.10). IMPORTANT: Check the coaxial cable for a possible short after soldering it to the PL-259 connector.
The only difference between the two is that the eight small holes around the 5/8" size hole are absent in the bracket for Model FQ-2 (see Figure 2.11). Next. Figure 2. 21 . Figure 2.11 Mounting bracket for Model FQ-2.12).12 Assembling the radiator portion. attach the plain washer (5/8" diameter) into the straight connector (see Figure 2. Assembly Attach the radiator element into the straight connector.The mounting bracket for Model FQ-2 is similar to that used for Model FQ-2.
13).13 Assembling the radial elements into the antenna base portion.Insert the straight connector into the eyehook ends of the brass radial elements.14). Insert the remaining portion of the straight connector into the mounting bracket you made earlier sandwiching the radial elements between the bracket and the plain washer (see Figure 2. Figure 2. Secure the whole assembly by connecting the other PL-259 connector into the protruding part of the straight connector.14 Assembling the antenna into the mounting bracket. 22 . Figure 2. The other ends of the elements must be slooping downwards (see Figure 2.
Installation Figure 2. 23 .16 Mounting the groundplane antenna Model FQ-2.
17 Spreading the radials. 24 . Figure 2.17).Spread the radial elements around with equal spaces between them and tighten the PL-259 to fix the assemby firmly (see Figure 2.
For example. The operator has to choose a type of antenna which is highly portable and at the same time functionally efficient in mobile operations. size. the situation around fixed installations allows the antenna to be constructed with durable and heavy materials to make it mechanically strong. ruggedness. However. Experience shows that one major factor influencing the overall design of antennas is the particularity of the situation where it will be used. That is how the FC-2 antenna was evolved. Perhaps being unhappy about the bronze rods protruding out of his small knapsack he cut each rod in half and devised an ingenious way of connecting the elements together during assembly. in mobile operation the situation drastically changes and using antennas designed primarily for fixed installations becomes impractical. Mobile operation imposes limitations on the design of an antenna regarding its weight.3 GROUNDPLANE ANTENNA 2 Model FCThe antenna is a vital link in the chain of radiocommunications and numerous designs have come off the drafting boards in a never ending search for improved performance. It is actually the same antenna just "compacted" further to make its total size smaller and more portable when disassembled. High power gain can also be easily attained by stacking a number of identical antenna. easiness in assembly and disassembly. This antenna was designed by a mobile radio operator several months after constructing his first groundplane antenna similar to Model FQ-2. 25 . and power gain. The groundplane antenna described in this chapter is another development from the FQ2 model.
It also retains the mechanical durability of the earlier full length version. The compact detachable elements of the Model FC-2 permit it to be carried inside a pack or bag for mobile operations. Materials needed The materials needed for Model FC-2 are the same with those needed for Model FQ-2. The only difference between the two is the additional 3/16 inch diameter brass rod which is used to interconnect the detachable elements of the Model FC-2. Figure 3. Being more compact it has become very popular among mobile radio operators.The electrical characteristics of this antenna is similar to those of Model FQ-2.2). After you have constructed the Model FQ2 disassemble it and cut the radiator and each radial element into two equal lengths (see Figure 3. 26 .2 Cutting the elements into two equal lengths. Refer to the preceeding chapter for the exact description of materials. Construction Fabricate a complete Model FQ-2 antenna following the construction methods described in the preceeding chapter.
Figure 3. Drill a hole about 1/8 inch diameter at one end of each connector rod.4 Drilling holes in the connector rods. take the 3/16" diameter brass rod and cut five 3/4 inch pieces from it. The hole must be about half the length of the connector rod deep (see Figure 3.3). Figure 3.4). 27 .Next.3 Preparing the connecting rods. These short pieces of brass rod will be used to connect the two equal lengths of each element (see Figure 3.
Repeat the same procedure for the remaining connector rods.the same deepnes with the first hole (see Figure 3.5).6 Making a thread in the smaller hole. secure the connector rod in a table vise and make a thread inside the smaller hole (the 3/32 inch hole to be sure) with a 1/8" gauge NF hand tap (see Figure 3. Figure 3.6). drill another hole about 3/32 inch diameter at the other end of each connector rod . Next.Next.5 Drilling a 3/32" hole in the other end of the connector rods. 28 . Figure 3. Repeat the procedure for all five connector rods.
8 Coupling the top half of the radiator element to a connector rod. NOTE: The purpose of this arrangement is to avoid the mistake of connecting the top half of the radiator to any of the radial elements.7).8). Figure 3.Insert the inner half rod of the radial element (the half part with the eyehook end) into the larger hole of the connector rod (1/8 " diameter hole unthreaded) and solder the two parts together. 29 . Figure 3.7 Coupling the connector rods to the radial elements. Insert and solder the top half of the radiator element into the larger half of the remaining connector rod (see Figure 3. Do the same with the other radial elements (see Figure 3.
The unit is comprised of a halfwave radiating element and a quarterwavelength matching section. its radiation pattern and characteristics are very similar to those of a halfwave vertical antenna. 33 . They are also resistant to corrosion. bronze or copper tubing. It is one version of a monopole antenna that carries its 'ground' along with it. This antenna radiates its signal in an omni-directional pattern like most vertical antennas do. The unit described in this chapter is designed for fixed installation. Its operational bandwidth is 140 . If you intend to use it for mobile operation it would be better if you modify the design to adapt it to the rugged environment it will encounter. It also exhibits a slight gain compared to a quarterwave groundplane antenna.4 J-FED HALFWAVE ANTENNA Model JF-2 This antenna is specifically designed to satisfy the need for a simple but effective vertical antenna which does not require any grounding system. These materials are more expensive but they are more durable.5:1 over the entire band. The combination of these two elements provides the transformer action that matches the impedance. Although it is actually a quarterwave antenna. Aluminum tubes in general are thin and soft and will easily crack if handled roughly so you must substitute it with brass.150 MHz and exhibits an SWR response of less than 1.
All points in the antenna element are electrically active so it must be insulated from ground.brass or GI with accompanying hex nuts and lockwashers Stove bolts .outside diameter ** idinside diameter 34 .see text to make a strip out of a short length of aluminum tube Plastic plate 1/2" thick see text for details U-bolt with accompanying hex nuts and lockwashers Stove bolts . Hanging the antenna under a tree or post will do.enough to hold 1" diameter tube 1/8" x 1" Dimensions 1" long 1/2" x 1-1/2" 1 3" x 12" 1 4 2 2 4 1 1/8" x 3/8" Miscellaneous: Epoxy glue *od. but there might be some other way that you can think of.brass or GI Eye terminals . You must also devise a method of mounting the antenna in a much simpler fashion than the one described here. Materials List Quantity 1 2 Specification/Description Aluminum or Brass tube 3/8" od* Aluminum strips .The elements must be cut in two or three sections and some means must be provided to join the pieces of tubing together in assembly (similar to FC-2 technique). never use any metallic material to mount the antenna. One word of caution though.vinyl insulated Plain washers .1/8" id** Hose clamp .
2 Bending one end of the tube.3).Construction Cut the tube to a length of 81 inches using a suitable tube cutter. starting from one end measure about 55 inches and starting at this point bend the tube to a U-shape. This method is employed to give an allowance for possible errors in bending the tube.2). Figure 4. Figure 4.3 Trimming the tube to its exact length. Next. Trim each arm of the tube to their proper lengths measuring from the extreme edge of the bend (see Figure 4. 35 . The two 'arms' of the bent tube must be spaced 2-1/8" apart from each other (see Figure 4.
Then follow it up with epoxy glue levelling it to the edge of the tube. 36 . Figure 4. First. Let the epoxy set and dry before proceeding. seal off both ends of the tube with an epoxy glue to avoid the entry of rainwater inside (see Figure 4. Figure 4.5 Sealing off the open ends of the tube with epoxy glue.4 Drilling holes in the tube.4). insert a substantial volume of cotton inside to act as a stopper for the epoxy. Each hole must be 1/8" in diameter.5).Drill four holes near the bend of the tube (see Figure 4. After drilling the holes.
The larger hole (3/16 " diameter) is intended for the U-bolts so their dimensions must coincide with the actual U-bolt used.6. Figure 4. Figure 4. Drill holes in the plastic plate following the dimensions shown in Figure 4.7 Fabricating a metal strip out of a short aluminum tube.6 Preparing the plastic mounting plate. prepare the plastic plate for the antenna mount.While you are waiting for the epoxy glue to dry. 37 .7). Fabricate a metal strip out of a short length of aluminum tube (about 5 inches long) by pressing it in a table vise until the tube is flattened (see Figure 4.
38 .8 Fabricating the clamps. Bend the two strips to a form of a clamp to fit tightly around the antenna tubing (see Figure 4. Figure 4. drill a hole about 1/8" diameter through the flattened end of each feedpoint clamp (see Figure 4.Out of this strip cut two short pieces (about 1-1/2" long). Next. Figure 4. These clamps serve as the feedpoint terminals of the antenna.9 A feedpoint clamp with a drilled 1/8" diameter hole.9).8).
Do not forget to include the necessary lockwashers in the attachment (see Figure 4. Be careful in tightening the nut because the tube is hollow inside and it might collapse damaging the tube.Assembly First. attach the J-shaped tube to the plastic mounting plate with 1/8" x 3/4" stove bolts made of corrosion proof materials such as brass or stainless steel. Apply torque to the nuts just enough to hold the tube rigidly. Attach the feedpoint clamps into both arms of the the tube. 39 .11 Feedpoint clamps attached to the antenna. Figure 4. Figure 4.10). Attach one clamp on the shorter arm of the tube and attach the other clamp on the longer arm (see Figure 4.11).10 Securing the J-shaped tube to the mounting plate.
Next step is to connect the coaxial cable to the feedpoint terminals. Figure 4.Attach a plain washer and an eye terminal into a stove bolt (1/8" x 3/16") then insert the bolt into the hole in the feedpoint clamp sandwiching the eye terminal inbetween (see Figure 4.12). Place a lockwasher and a hex nut at the other end of the bolt then tighten the clamp lightly. Figure 4. Prepare one end of the coaxial cable by separating the braid/shield from the inner conductor (see Figure 4. 40 . Repeat the same procedure for the other clamp.12 Assembling the feedpoint terminals.13).13 Making a pig tail.
The coaxial cable must be furnished with the right connectors for the particular type of SWR meter you use. The braid must be connected to the shorter arm of the tube and the inner conductor must be connected to the longer arm (see Figure 4. move both feedpoint clamps higher or lower than the initial setting until you get a low SWR response over the entire frequency range (140.15). Set the transceiver to 145.14 Connecting the coaxial cable to the feedpoint clamps. Note the SWR reading on the meter. I IMPORTANT: Do not move the clamps while the rig is transmitting and do not touch any part of the antenna when reading the SWR response. The position of the clamps must be moved always at the same level at the same time. Mount the antenna to the mast you intend to use. Figure 4.00 MHz to 150.00 MHz and key the PTT to transmit. It is best to tune the antenna to resonance right at the mast where it will be installed permanently. Connect a transceiver to the input connector of the SWR meter (usually marked 'transmitter').00 MHz) specifically).14). 41 . While the transceiver is on standby . Move the clamps about 1/4" at a time (see Figure 4.Insert and solder the two conductors (braid and inner conductor) to the eye terminals attached in the feedpoint clamps. Connect the coax cable to an SWR meter.
Figure 4.15 Adjusting the position of the clamps to tune the antenna. 42 .16 Final mounting of the J-fed antenna. Figure 4. After you have tuned the antenna to resonance. tighten the nuts holding the feedpoint clamps permanently and fix the coaxial cable to the mounting plate with plastic clamps (see Figure 4.16).
it recieves signal equally well from all directions. with the inner conductor of the coaxial cable connected to the radiating element and the shield connected to the tube.1 show how the coaxial dipole was evolved from a basic dipole antenna. It exhibits an SWR response of less than 1. The CD-2 coaxial dipole has an operational bandwidth of 140-150 MHz. This unit is designed to be installed primarily in base stations but it could be used for mobile applications too. It has a power gain of 1 dB (unity gain) compared to a standard dipole reference. It has also a narrow form which some radio operators find beautiful. The following illustrations in Figure 5. The tube functions as a groundplane. The RF signal radiates from the antenna in an omni-directional pattern. The coaxial transmission cable is then inserted through this tube.5 COAXIAL DIPOLE Model CD-2 The coaxial dipole described here has the advantage of having lower resistance to wind compared to the groundplane designs. one of the elements is enlarged to form a tube. 43 . The radiating element must be detached when transporting the antenna.1 Evolution of the coaxial dipole from a basic dipole antenna. Likewise.5:1 over the entire band. As you can see in the illustration. Figure 5.
3 Cutting the tubes to their proper lengths.see main text for exact dimensions U-bolts .the brass rod for acetylene welding is recommended Aluminum bushing .outside diameter Construction First prepare the two aluminum tubes of different diameters. Cut the tubes to their proper lengths as shown in Figure 5.with accompanying hex nuts and lockwashers Aluminum Plate or GI Self tapping metal screws Short length of coaxial cable RG-58/U 3" x 6" 1/8" x 1/2" 37" long Dimensions 3" x 18" 1" x 36" 2 4 1 9 1 *od.3 Figure 5. 45 .Materials List Quantity 1 1 1 2 1 Specification/Description Aluminum tube Aluminum tube PL-259 VHF male connector SO-239 VHF female connector Brass rod 1/8" od* .
The holes must be equally spaced from each other (see Figure 5. Figure 5.Next. Figure 5.5).5 Drilling a hole at one end of the short tube.4 Drilling three holes at both ends of the long tube. The holes must be 1/4" away from the edge and equally spaced from each other (Figure 5. Drill three holes (1/8" diameter) at one end of the shorter tube. drill three holes (1/" diameter) at both ends of the longer tube. 46 .4).
Figure 5. Follow the dimensions in Figure 5. Figure 5. 47 .7. Next. machine the larger bushing from similar material.6.7 Dimensions of the larger bushing.6 Smaller bushing dimensions.Machine the smaller bushing from a thick aluminum slab or rod to its proper size. Follow the dimensions shown in Figure 5.
8 Soldering the radiator element to the PL-259. You need only the vinyl outer jacket. 48 .9 Inserting the insulating jacket into the PL-259.8).9).File away a small portion at one end of the brass rod reducing it to smaller diameter enough to fit inside the center pin of PL-259 connector. Figure 5. Figure 5. Solder the brass rod into the center pin of the PL-259 connector (see Figure 5. Insert it into the brass rod all the way inside the PL-259 connector. The jacket serves as an insulator between the brass rod and the body of PL-259 (see Figure 5. Cut a small length of coaxial cable (about 2 inches) and remove its inner conductor and braid/shield. Cut away any protruding vinyl portion.
Let the epoxy set and dry.10 Sealing the PL-259 with epoxy glue. Don't forget to include its grounding ring or solder lug.11.11 Mounting the SO-239 into the larger bushing.10). The epoxy serves as a sealant to avoid the seepage of rainwater inside the PL-259 connector. Assembly First attach the two SO-239 connectors into the two aluminum bushings as shown in Figure 5. Figure 5. Figure 5. 49 .Mix equal amount of epoxy glue and place it over and around the protruding part of the vinyl jacket (see Figure 5.
Lay the coaxial cable and the longer tube side by side as they would be when they are finally assembled together.Cut a 36 inches long coaxial cable (RG-58/U) and solder its conductors at one end to the SO-239 connector attached to the larger bushing (see Figure 5. 50 . Trim the free end of the coaxial cable at the point 3/8" away from the end of the longer tube (see Figure 5.13 Trimming the coaxial cable to the proper length.12 Soldering the coaxial cable to the SO-239. Figure 5.13).12). Figure 5.
If in your first try you did not manage to align the holes then maybe a slight retrimming of the coax cable is needed or the SO-239 connector must be repositioned or resoldered. 51 .14 Soldering the other end of coaxial cable to the other SO-239. After a few trials you should have done it right (see Figure 5. coaxial cable and the large bushing all the way inside the longer tube until the holes in the two bushings are aligned to the holes in the tube itself. Figure 5.15 Inserting the feeder coaxial cable into the long tube.Solder the free end of the coax cable into the remaining SO-239 connector attached to the smaller bushing (see Figure 5. Figure 5.15).14). Insert the smaller bushing.
16). Figure 5. 52 .16 Securing the bushings and the tube together. Align the holes in the large bushing to the holes in the shorter tube and place self-tapping screws through the holes to fix the bushing firmly inside the short tube.Secure the two bushings permanently into the tube using self-tapping metal screws (see Figure 5. Insert the longer tube and the large bushing inside the shorter tube (see Figure 5.17). Figure 5.17 Assembling the two tubes together.
53 .18 Installing the radiator element into the antenna base. Figure 5.18).Attach the radiator element to the SO-239 connector in the upper larger bushing (see Figure 5.
Installation of Model CD-2 Figure 5.19 54 .
55 . Gamma matching is based on the principle of delta match system where the transmission line can be directly connected near the center of a continuous halfwave conductor and fanned out and tapped at the point of most efficient power transfer. Fine tuning of the antenna can be done by adjusting the shorting bar that connects the gamma tube to the dipole element until the lowest SWR response is achieved. that is to match the impedance of the transmission line to the impedance of the antenna and to couple the unbalanced coaxial cable to the symmetrical dipole element. The gamma match therefore achieves two functions at the same time. The middle of a halfwave dipole is electrically neutral meaning there is no RF voltage present so the outer conductor of the coax cable can be connected directly to the element at this point. The inner conductor of the coaxial cable carries an RF current so it is tapped into the dipole element at the matching point.6 GROUNDPLANE ANTENNA (gamma fed) Model DP-2F This particular design of a dipole antenna is very popular in VHF applications because of its capability to be fine-tuned during tuning procedures. This method makes it unnecessary to use a separate balancing transformer. After a careful observation of this design you will notice that the center conductor of the coax cable is not directly connected to the dipole element but instead coupled via a short tube called "gamma tube". The combination of the short tube and the coaxial cable inside it provides the capacitance needed to cancel the inductance of the dipole element to attain an electrical balance. Tuning is accomplished by a so-called gamma matching system connected near the center of the dipole element.
It has a gain of 1 dB (unity gain) compared to a standard dipole reference.brass or GI Hex nuts .4:1 over the entire band. Lightning protection for this antenna system is also improved because all the metallic parts of the antenna are grounded via its mast or tower.Model DP-2 is also used as a basic driven element for high gain Yagi and collinear antenna designs. If properly tuned it exhibits an SWR of less than 1. it does not require to be insulated from its mounting boom thereby simplifying the mechanical construction. However.see text for fabrication Coax cable RG-58/U BNC female connector Stove bolts . Materials List Quantity 1 1 1 1 Specification/Description Aluminum tube 3/8" id* Aluminum tube 3/8" id* Aluminum square channel Aluminum strip . This antenna is intended primarily for fixed installations. The dipole design described in this chapter is designed to operate in the frequency band of 140-150 MHz. If you are the experimenter type of radio operator then this design is for you.brass or GI U-bolt with accompanying hex nuts and washers Self tapping metal screws 1/8" x 1/2" 1/8" x 3/8" 1/8" id Dimensions 38" long 6" long 1" x 1" x 12" 1/2" x 4" 1 1 2 2 1 6" 3 Miscellaneous: Epoxy glue *id. Because the middle of the dipole element is electrically inactive. Some antenna constructors choose to build this antenna because it presents them deeper understanding of the electrical principles of antennas compared to other simpler designs like groundplanes or coaxial dipoles.inside diameter 56 . some radio operators were able to use it succesfully in mobile operations by modifying its mechanical construction. It radiates its signal in an omni-directional pattern.
The hole is 3/8" and slightly oversized so that the tube will not be scratched upon insertion but not too loose as to sacrifice rigidity.2). Next prepare the mounting channel by drilling a hole at one end (see Figure 6. 57 .2 Drilling a hole through the middle point of the radiator element. Figure 6. Figure 6.3). Drill a hole (1/16" diameter) through and through at the middle of its length (see Figure 6.3 Preparing the mounting channel.Construction The radiator element is made from 3/8 od* aluminum tube cut to a length of 38 inches. The diameter of the hole must accomodate the aluminum tube that will be inserted into it.
Drill another pair of holes (3/16" diameter) at the same side but at the opposite end of the channel (see Figure 6. Drill the hole through and through.5).4 Drilling holes for the gamma mounting bracket. Figure 6. drill two small holes (1/16" diameter) at one side of the channel perpendicular to the axis of the bigger hole (see Figure 6. The size of the holes and the distance between them must conform to the dimensions of the U-bolt used. Figure 6.4).5 Drilling holes for the U-bolt at the opposite end . 58 .Next.
7 Inserting the aluminum tube into the mounting channel. See dimensions in the following illustration.6 Drilling a single hole.7).Drill a single 1/8" diameter hole at the other side opposite to the two small holes (1/16" diameter). Figure 6. Figure 6. Insert the aluminum tube through the large hole and align the hole at its middle part to the 1/8" diameter hole at the side of the channel (see Figure 6. 59 .
Insert a self tapping screw through the sidehole and forcibly screw it into the smaller hole of the tube inside (see Figure 6. Prepare the feedpoint angle bracket.9 Preparing the feedpoint bracket (gamma mounting bracket). An alternative method is to saw off a portion of a 1" x 3" rectangular aluminum channel. The bracket is cut from a small strip of aluminum and bent into a right angle. This will give you a more durable bracket with a near perfect angle.8 Locking the tube with a self tapping screw.8). Tighten the screw until the aluminum tube is rigidly held in the aluminum channel. Figure 6. Figure 6. 60 .
61 . This lone hole must be large enough to accomodate the BNC female connector (see Figure 6.11). Figure 6.10 Drilling mounting holes in the bracket. Figure 6.Drill two small holes (1/8" diameter) at one side of the angle bracket. Attach the bracket into the mounting channel by screwing it with small self tapping screws (see Figure 6.10).11 Fixing the feedpoint bracket on the mounting channel. Drill another hole at the other side of the bracket.
62 . Cut about 4 inches of the flat strip and form both ends to a ring clamp by bending it around an aluminum tube.13).13 Preparing the tuning clamp.12). Next step is to prepare the tuning clamp and the gamma matching tube. Figure 6. fabricate a flat strip from a scrap tube (about 4 inches long) by pressing it in a table vise until it is completely flattened.Insert the BNC female connector in an upside down position into the large hole of the feedpoint bracket and secure it with its nut (see Figure 6. The ends must be formed to fit around the tube (see Figure 6. First.12 Installing the BNC connector into the feedpoint bracket. Figure 6.
Insert the 6 inch long tube into one loop of the clamp and secure the clamp with a 1/8" x 3/8" stove bolt. Don't tighten this bolt too much at this time! Figure 6.14 Drilling holes in the tuning clamp.14).15).Drill two holes (1/8" diameter) in the tuning clamp (see Figure 6.15 Inserting the 6 inch long gamma tube into the tuning clamp. 63 . Attach a nut to the bolt and tighten it lightly (see Figure 6. Figure 6.
17). Cut away a small portion of the PE inner insulator exposing the copper conductor inside (see Figure 6. While the epoxy is drying. Place epoxy glue over the cotton wad inside. Figure 6.Waterproof the top end of the 6 inch gamma tube by inserting a substantial volume of cotton wad inside the open end. Let the epoxy set and dry (see Figure 6.16 Sealing the top end of the gamma tube. The cotton wad serves as a stopper for the epoxy. Figure 6. 64 .17 Preparing the gamma match from a short length of RG-8/U. prepare the gamma match from a short length of RG8/U coaxial cable.16). Cut a piece 6 inches long and remove its vinyl outer jacket and its braid.
Figure 6.19). insert the gamma match into the gamma tube (see Figure 6. carefully insert the free end of the tuning clamp into the radiator element (long tube) starting at the top end. 65 . Next.Solder the exposed copper conductor of the gamma match directly into the center pin of the BNC connector attached to the mounting channel.18 Soldering the gamma match into the BNC connector. As the tuning clamp is lowered down along with the gamma tube attached to it.
install it to the mast or tower following Figure 6. Figure 6.19 Assembling the gamma tube into the gamma match. Insert a bolt into the tuning clamp attached around the radiator element and tighten it lightly enough to hold the gamma matching assembly in place. it only needs to be tuned to resonance for proper operation. 66 . Connect a VHF transceiver to the SWR meter (usually marked 'transmitter') and set its frequency to either the center or extreme frequencies of the band. Key the PTT to transmit and read the SWR response. Connect the coaxial cable to the BNC connector in the angle bracket and connect the other end to a suitable SWR meter. The antenna is already mechanically ready at this point.Stop the gamma tube just about 1/2 inch above plane of the angle bracket or just enough for the gamma tube to cover the whole PE insulator. In tuning the antenna to resonance.1.
67 .21).20 Raising or lowering the tuning clamp to find the best match. Move the tuning clamp either lower or higher about 1/4 inch at a time (see Figure 6. If you have finally found the right position (after several trials) then you have succesfully tuned the antenna to resonance. Figure 6.20).To tune the antenna: move the tuning clamp and find the position where you can get the lowest SWR response for the center frequency and a relatively flat response curve over the entire band. Tighten the nuts at the tuning clamp permanently and place a moderate amout of silicone sealant (RTV compound) around the open lower end of the gamma matching tube to seal it off from moisture and rainwater (see Figure 6.
I n n IMPORTANT: Do not touch any part of the antenna while keying the rig or reading the SWR response.Figure 6. 68 . Do not move the tuning clamp while the transceiver is still transmitting.21 Sealing off the lower end of gamma tube with silicone.
On the other hand other element forms may also be used to effectively function as an antenna. 69 .7 QUADLOOP ANTENNA Model QA-2F In preceeding chapters all of the various antenna designs presented are assemblies of linear halfwave (or approximately halfwave) dipole elements. Figure 7. This is the type of antenna with a radiating element made of a loop having a perimeter of one wavelength and used in much the same way as a dipole. One example is the quad antenna described in this chapter.1 A quad loop antenna model QA-2F.
Drill additional holes (1/8" diameter) in the tube as shown in the following illustration (Figure 7. Figure 7.7 Drilling additional holes in the tube. 73 .7).6 Flattening and drilling the ends of the tube. The holes must be drilled through and through. Be careful in drilling the holes to avoid deforming the tube.6). Figure 7.Flatten a small portion at both ends of the tube and drill a hole (1/8" diameter) in each flattened end (see Figure 7.
Figure 7.Insert two stove bolts (1/8" x 3/8") through the holes at both ends of the loop and attach the necessary hardware as shown in Figure 7.8 Installing the necessary hardware at both ends of the tube.9 Fixing the loop on the plastic mount. Figure 7. Attach the prepared loop into the plastic mounting plate by bolting it through the 1/8" diameter holes as shown in the following illustration.9. Use 1/8" x 1" stove bolts (brass or stainless steel).8. See Figure 7. 74 .
10 Connecting the coaxial cable to the loop element.11). Solder the two conductors to the two eye terminals in the loop.Prepare one end of the coax cable by separating the inner conductor from the copper braid. Figure 7. 75 . Figure 7. The braid is costumarily connected to the lower terminal (see Figure 7. Clamp the coaxial cable to the plastic mounting plate (see Figure 7.11 Clamping the coaxial cable to the plastic mount.10).
Installation of QA-2F Figure 7.12 Installing the QA-2F to the mast. 76 .
The thin metal strips used to clamp the two overlapping edges of the cone is for mechanical reasons only. Its signal pattern is similar to that of a quarterwave groundplane antenna. In designing the discone. The discone antenna described in this chapter is made of wirescreen mesh. Specifically speaking. The discone antenna is a broadband antenna. Amazing! Well.the RF waves travel down to the cone edge and not around it.8 DISCONE ANTENNA Model CD-2W Most of the antenna designs described in the preceeding chapters are all suitable for VHF work requiring omni-directional pattern of radiation. This problem can be solved by using a discone antenna described in this chapter.4 Gigahertz! The lowest operational frequency is called cut-off frequency. these designs are simple and easy to construct which makes them very popular among radio operators. Radiowaves from the transmission line emerge at the feedpoint (cone apex) and travel along the antenna surface to the edges of the cone and disc. Meaning it can operate over a wide range of frequencies. Also in the mechanical viewpoint. Theoritically. a discone antenna can achieve that because it functions more like a transformer than a conventional antenna. so an electrical connection is not important. It couples the low impedance transmission line to the higher impedance of free space. This material is purposely used to minimize the effect of wind to the antenna. Although this handicap can be avoided by using a different antenna tuned to a different frequency band. the dimensions of the antenna are carefully computed so as to make the impedance at its edges similar to that of free space. a properly designed discone antenna can operate up to a frequency 10 times the value of its lowest operational frequency. If one attempts to operate his transceiver outside these frequency limits (assuming he has a wideband transceiver) the signal response becomes weaker as the operating frequency of the transceiver is moved farther away from the operational bandwidth of the antenna. However all of them have a limited bandwidth of 140-150 MHz. Below this frequency the SWR will increase rapidly. the process of changing antennas everytime the operator changes his operating band becomes time-consuming and cumbersome. if a discone antenna is designed to operate with a lowest operational frequency of 140 MHz. 77 . At the same time the SWR in the transmission line increases and can reach an intolerable point which may cause damage to the transceiver. then it can be conveniently used up to 1. Naturally the discone radiates a signal because there is a maximum transfer of energy when impedances are matched.
Power gain is 1 dB (unity gain) and its installation is fixed. The discone antenna does not need tuning after construction. SCALED DOWN APPEARANCE Figure 8.This unit has an operational frequency bandwidth of 140 MHz up to 1.1 78 . SWR is measured to be less than 2:1 over the entire bandwidth. It is also popular for use in automatic scanning wideband monitors.4 Gigahertz although best results can be obtained if its use is limited up to 1 Gigahertz only.
brass or GI Hex nut 1/8" id* Hose clamp .Materials List Quantity 1 Specification/Description Aluminum or GI wire screenmesh medium gauge .aluminum (customized dimensions see text) Plastic bushing (customized dimensions see text) Stove bolt .inside diameter 79 .stainless steel Metal plate 1/8" thick Aluminum strip gauge 14 or 16 U-bolt with hex nuts and lockwashers Dimensions 1 1 1 1 2 1 25" long 30" long 1 1 1 1 1 2 4 1/8" x 1-3/4"+ 1-1/2" diameter 3" x 6" 1/2" x 22" *id.enough to support itself without reinforcement Aluminum tube 1" id* PL-259 VHF male connector PL-258 VHF straight connector Coaxial cable RG-58/U Eye terminals 1/8" Washer .
3.3 Plastic bushing dimensions. prepare the customized aluminum washer to be used as a disc holder. Machine it according to the dimensions shown in Figure 8. Figure 8. 80 . Next.2 Customized aluminum washer dimensions.Construction First. Figure 8. Machine it from a thick aluminum plate or rod following the dimensions shown in Figure 8.2. prepare the plastic bushing from a small piece of engineering plastic rod with the required diameter.
The tube must be 1" in diameter and 25 inches long. Figure 8. This hole will accomodate the screw to hold the coaxial braid inside the tube as described later in the final steps.Next.5 Drilling the hole which accomodates the coaxial braid lockscrew.4 Drilling holes at one end of the mounting tube. 81 .5). prepare the aluminum mounting tube. Drill three holes (1/8" diameter) around one end of the tube with the holes equally spaced between each other (see Figure 8. Drill a single hole (1/8" diameter) at the same end but slightly lower than the first three holes (see Figure 8.4). Figure 8.
12). Insert the free end of the coaxial cable into the mounting tube starting from the tube's end with sideholes (see Figure 8.13 Inserting the coaxial cable into the mounting tube. 85 .Cut a 30 inches long RG-58/U coaxial cable and solder the inner conductor at one of its ends into the eye terminal held by the bolt below the plastic spacer.12 Connecting the coaxial cable to the top disc element.13). Figure 8. Figure 8. Attach a vinyl insulated eye terminal into its braid (see Figure 8.
Insert the plastic spacer/bushing holding the top disc element inside the tube and align its hole to the tube's sideholes.15 Securing the braid inside the mounting tube. Align the lower hole to the eye terminal of the braid inside the tube.14 Securing the top disc element to the tube. This procedure is the main reason why you should use an eye terminal with a 1/16" diameter eye. Figure 8. Tighten the screw to hold the terminal firmly (see Figure 8. Figure 8. If it is not aligned yet.15). insert a slender stick inside the tube and remotely move the eye terminal until you can see it through the hole outside. Fix the bushing to the tube per-manently using metal screws (see Figure 8.14). Insert a metal screw into the hole and turn it until it catches the eye terminal inside. 86 .
Solder a PL-259 to the free end of the coax cable and connect a straight connector (PL258) into it prior to the final installation of the antenna (see Figure 8. coaxial cable and the mounting tube into the cone starting from the top until the apex of the cone reaches just a tiny fraction of an inch below the plastic bushing holding the top disc element (see Figure 8. Finally.16 Connecting the PL-259 and PL-258 to the coaxial cable.16). Figure 8. insert the PL-259. 87 . Figure 8.17 Inserting the mounting tube into the cone element.17).
Attach the stainless clamp around the upturned portion of the wiremesh just under the disc.18 Clamping the apex of the cone element to the mounting tube. 88 .18). Figure 8. Trim the excess wiremesh protruding above the edge of the tube clamp (see Figure 8. Tighten the clamp to hold the cone in place.
The only trade-off is the total cost of the antenna because metal plate is more expensive. The only and obvious difference between the two models is the utilization of a metal plate for the disc and cone elements of CD-2P (P for plate).meaning if your area is regularly visited by heavy rainfall or strong winds. This is a precautionary measure to avoid a lightning striking your antenna and possibly causing damage to your transceiver or to you.but don't paint the aluminum mounting tube under the cone element to ensure adequate grounding connection of the antenna to the mast or tower. just do it . In most occasions. 90 . a GI metal plate is satisfactory but you can also use a more expensive aluminum plate if you desire so. then you must opt to construct and install this more robust model than the wire-screen version.9 DISCONE ANTENNA Model CD-2P The discone antenna model CD-2P described in this chapter is functionally similar in most respects to the discone antenna in chapter 8. Metal plate is more durable than a wire-screen. Aluminum is less susceptible to corrosion so it is highly recommended if you plan to use the antenna near seashores or in places where there is a high level of salt present in the surrounding moisture. The choice of using a metal plate becomes evident when the antenna is intended to be installed in areas with less than excellent weather conditions . Paint has a negligible effect on the RF signal so if you decide to paint the antenna to make it look attractive.
Cut the cone and disc elements out of the thin metal sheet following the dimensions shown in Figures 9. Figure 9. Construction In constructing most of the parts of CD-2P. follow the instructions for the Model CD-2W except those for the disc and cone elements.2 and 9. Also the two thin metal strips are not needed. 91 .Materials needed The materials necessary for the antenna Model CD-2P are the same with those needed for CD-2W except for the wire mesh for the cone and disc which is replaced with a thin metal sheet in CD-2P.2 Disc element dimension. However you have to retain the blind rivets for the same purpose.3.
Cut a metal sheet and shape it to a form of a ring as shown in Figure 9.Figure 9. 92 . Unlike the wire mesh cone of CD-2W.4 Preparing the sleeve.3 Cone plate dimensions. the cone for CD-2P must have a metal sleeve soldered to the opening at the apex.4. Figure 9.
Figure 9.6).5 Soldering or welding the sleeve to the apex opening of the cone. The assembly of CD-2P is similar to the steps for assembling the CD-2W (see Figure 9.5).Solder this sleeve to the rim of the apex opening leaving a small gap between their ends (see Figure 9.7 93 Assembled CD-2P. . If you are using an aluminum plate for the cone and sleeve. you need to electrically weld the two pieces together using a special technique for welding aluminum with protective gas. Figure 9.
Never use a metallic wire to hang the antenna because it will distort the radiation pattern of the signal or short out the disc and cone elements. Those seemingly small items like portable transceiver. then the U-bolts intended for mounting may be discarded. the antenna can be tied with a thin nylon rope on its mounting tube near the feedpoint and hung under a post or branch of a tree. The actual length of a packed discone is merely 8 inches! When the telescopic rods are extended to their maximum length and set in the proper angle. could easily total up to more than 20 kilos of deadweight if cramped together inside a single backpack. Experience showed however that three elements for each disc and cone function are enough on most occasions. charging box. coaxial cable. 94 . log books. solar panels. This portable version of a discone antenna has the same electrical characteristics with the two full-sized models described in chapters 8 and 9. The antenna model described in this chapter is specially designed to satisfy the need for a lightweight and transportable discone antenna. The chrome plated telescopic rods are quite expensive so the total cost of this antenna is higher than the two preceeding models. scanning monitor. etc. Theoritically the more elements used the better. Add to it the supply of food and few personal belongings and it will surely feel like a nightmare when travelling across a rugged terrain. The over-all bulk of the load is another problem.10 DISCONE ANTENNA Model CD-2T In mobile operations the problems related to antenna installation are much greater than those encountered in fixed stations. Just imagine travelling while lugging a full-size metal plate discone at your back! Because of this. spare batteries. The only difference is in the mechanical construction. If this antenna will be used solely for mobile operations. Instead. The problems are worse particularly for a one-man-mobile-station which travels on foot. The cone and disc elements are replaced with retractable telescopic rods so that the antenna can be collapsed into a small unit and conveniently stored inside a backpack. myriad of wires. they approximate the function of a full disc and cone elements. the tendency of mobile operators is to bring only the most important piece of equipment and is usually a portable and lightweight version to trim down the total weight and bulk of the load.
Scaled down appearance Figure 10.1 95 .
see text for customized dimensions Aluminum cone base mount see text for exact dimensions PL-259 VHF male connector PL-258 VHF straight connector Aluminum plate 1/8" thick Eye terminals .with swivelling threaded base Aluminum disc base mount see text for exact dimensions Plastic spacer .no insulation U-bolts with accompanying hex nuts and lockwashers Stove bolt .with swivelling threaded base Telescopic antennas .brass or GI Self tapping metal screws Self tapping metal screw Hex nut .brass or GI 1/8" x 2" 1/8" x 3/8" 1/8" x 3/4" 1/8" id* 3" x 6" Dimensions 7" fully extended 3-5" retracted 22" fully extended 5-6" retracted 3 1 1 1 1 1 1 2 4 1 6 1 1 *id.inside diameter 96 .Materials List Quantity 3 Specification/Description Telescopic antennas .
2 Disc base mount dimensions. Figure 10. Figure 10. prepare the plastic spacer/bushing from a piece of an engineering plastic. 97 .3 Plastic spacer dimensions.2). prepare the top disc elements base mount by machining an aluminum rod to the necessary dimensions. Second. The size of the holes (holes marked with a) and their thread gauge must conform to the dimensions of the short telescopic antenna you intend to use. This plastic spacer insulates the disc base mount from the cone base mount.3. Machine it to the form and dimensions shown in Figure 10. Follow the dimensions shown in the illustration (Figure 10.Construction First.
thread gauge. Figure 10. the plastic spacer and the cone base mount together following the arrangement shown in Figure 10. Secure the assembly with self tapping screws to the appropriate holes as illustrated. Machine it to the form and dimensions shown in the following illustration (Figure 10. 98 .Next step is to prepare the cone elements base mount from an aluminum rod with the necessary size. Figure 10. and deepness of the holes at the side (holes marked with a) must conform to the base dimensions of the particular type of telescopic antenna intended for the cone elements.4).5 Assembly of the elements' base mounts.5.4 Cone elements base mount dimensions. The size. Assemble the disc base mount.
Figure 10.Attach the remaining eye terminal to the lone hole at the rim of the cone base mount (see Figure 10. Never interchange the connection. Figure 10. 99 .7). The inner conductor must be soldered to the center terminal and the braid must be soldered to the eye terminal at the rim (see Figure 10. Solder one end of the coax cable to the two terminals at the base mount assembly.6).7 Connecting the coaxial cable to the terminals.6 Eye terminal attached to the rim of the cone base mount.
9). Insert the aluminum base mount assembly into the tube and align the holes at the sides. Place screws through the holes to permanently attach the base mount assembly into the tube (see Figure 10. Insert the free end of the coax cable inside the aluminum tube starting at the end with sideholes. 100 . Figure 10.8 Preparing the mounting tube.8). The holes must be equally spaced from each other. Drill three holes (1/8" diameter) at one end (see Figure 10.9 Fixing the base mount assembly into the tube. Figure 10.Next step is to prepare the aluminum mounting tube by cutting it to a length of 6 inches.
10). Figure 10.Solder the PL-259 to the free end of the coaxial cable and attach a straight connector (PL-258) into it (see Figure 10. Figure 10.11). Attach the three short telescopic antennas into the disc base mount (see Figure 10. 101 .10 Connecting the PL-259 and PL-258.11 Telescopic antennas attached to the disc element mount.
Similarly.12). 102 .12 Attachment of long antennas to the cone element mount.Next.13 Mounting the completed antenna to the mast. extend the three long telescopic antennas to their full lengths but they must be bent to about 60 degrees angle drooping downwards to the ground.13. attach the three long telescopic antennas into the cone base mount under the first set of antennas (see Figure 10. Figure 10. Attach the assembled antenna to the mast by using the aluminum mounting plate and one U-bolt. Extend the top telescopic antennas to their full lengths maintaining them in horizontal position. See Figure 10. Figure 10.
To carry the CD-2T in collapsed form for transportation. 103 .14 Antenna CD-2T in collapsed form.14). retract all the telescopic elements and bend them towards the mounting tube (see Figure 10. Figure 10.
A version of a 5/8 vertical with radials is presented in this chapter. It is omni-directional and can be used either with radials or a solidplane body (such as the one afforded by a car). All of the materials used in this model are readily available at hardware stores and can be bought cheap. When the contact is finished the transceiver is again switched back to the 5/8 wave vertical antenna. The two antennas are connected to a common transceiver via a switching box. In comparison. It has a gain of 1. It is designed for fixed station installations. The common practice of radio operators is to install this antenna atop a tower with rotatable Yagi arrays positioned a few feet below it. Only one antenna is active at one moment.8 dB over a standard dipole reference. a commercial version of this antenna costs more than a thousand pesos! This antenna model WA-2 is designed to operate in the 140-150 MHz VHF band. It exhibits an SWR of less that 1. This does not mean however that the average radio operator who cannot afford to erect a tower and a Yagi array should refrain from installing a 5/8 wave vertical.11 5/8 WAVE ANTENNA Model WA-2 Probably one of the most popular vertical antennas for both mobile and fixed station installations is the 5/8 wavelength vertical because it has some gain over a dipole. The 5/8 wave vertical is used as a monitoring antenna because of its omni-directional characteristics. A properly constructed 5/8 wave vertical antenna if used singly works perfectly well! Perhaps one advantage of constructing this antenna by the radio operator himself is the over-all cost of the unit. the operator quickly switches over to the Yagi antenna and beams it towards the other station to optimize communications.5:1 over the entire band if properly tuned. Once a contact has been established during operation. 104 .
inside diameter 106 .Figure 11.4" long 1" id* x 8" 20" long 3" x 6" 28 " long Dimensions 3 1 1 1 1 1 1 1 4 1 1 6 1 1 * id .brass or GI Self tapping metal screws Eye terminal vinyl insulated Short hook-up wire 12" long 1/8" x 3/8" 1/8" x 3/8" 1/16" id* 3".see text for dimensions Aluminum tube Copper wire gauge no. 14 Aluminum plate 1/8" thick U-bolts with accompanying hex nuts and lockwashers Coaxial cable RG-58/U Stove bolt .1 Materials List Quantity 2 Specification/Description Brass rods 1/8" diameter the brass rod for acetylene welding is recommended Brass rods 3/16" diameter Engineering plastic rod see text for dimensions PL-259 VHF connector PL-258 VHF straight connector Aluminum bushing .
3 Aluminum bushing dimensions.Construction First prepare the plastic coil form by machining the engineering plastic rod to the dimensions shown in Figure 11. Figure 11. Next. Figure 11.3.2.2 Coil form dimensions. prepare the bushing by machining the aluminum rod to the dimensions shown in Figure 11. 107 .
Secure the assembly with metal screws. Join and solder the two notched ends together to make a long single rod (see Figure 11. Prepare the radiator element.4 Assembling the coil form and the bushing together. File a notch at one end of each 1/8" diameter brass rod.5 Joining the two brass together to make the radiator element.Assemble the plastic coil form and the aluminum bushing together. Screw only through the two holes and temporarily leave the third hole unscrewed (see Figure 11. Figure 11.4).5). 108 . Figure 11.
Insert one end of the radiator rod into the top hole in the plastic coil form. Figure 11.6 Securing the radiator element into the coil form. Screw forcibly the 1/8" x 3/8" stove bolt through the hole at the side of the plastic coil form pressing the brass rod inside to hold it firmly (see Figure 11.7). 109 .6). Cut the brass rod to a length of 46 inches measuring from the point where it emerges from the plastic form (see Figure 11.7 Cutting the radiator element to its proper length. Figure 11.
Figure 11. After you have soldered the eye terminal. Wind 10 and 1/2 turns evenly spaced and distributed to cover most of the length of the plastic form.8).Wind the No. attach it into the aluminum bushing with a metal screw (see Figure 11. Figure 11. 14 copper wire around the coil form. The eye terminal must be positioned in such a way that its eye is aligned with the unscrewed hole in the aluminum bushing.9).8 Winding the coil around the coil form. Solder the top end of the copper wire to the base part of the brass rod (see Figure 11. Solder an eye terminal to the lower end of the copper coil. 110 .9 Securing the coil to the aluminum bushing.
111 . Solder the upper end of the hook-up wire to approximately 6 and 1/2 turns counting from the coil's lower end connected to the aluminum bushing (see Figure 11. Cut 12" length of coaxial cable RG-58/U and separate the braid from the inner conductor at one end (make a pig tail).10 Tapping the coil for feedpoint.11). Insert it into the hole in the plastic coil form until it protrudes from the center hole at the bottom. Figure 11. After joining the two wires. This connection is temporary only and it may be necessary to move the wire during tune-up procedure. insulate the joint either with a shrinking tube or just a plain vinyl tape.Cut a short length of stranded hook-up wire (about 3 inches). Solder an eye terminal into the braid of the coax cable (see Figure 11. Figure 11.10).11 Connecting the coaxial cable to the hook-up wire. Solder the inner conductor into the hanging end of the hook-up wire at the bottom of the plastic form.
insert the bushing inside the tube and align the holes at their sides. Secure the bushing into the tube by screwing self tapping screws into the holes (see Figure 11.13 Securing the aluminum bushing into the mounting tube. Figure 11. Drill a single hole at the same end but slightly below one of the first 3 holes (see Figure 11.12).12 Preparing the mounting tube.13).Next step is to prepare the mounting tube. The holes must be 1/8" in diameter and equally spaced from each other. insert the free end of the coaxial cable into the mounting tube starting at the end with sideholes. 112 . Figure 11. When the aluminum bushing and tube meet. Next. Cut 1" diameter tube to a length of 12 inches and drill three holes at one end.
Note that these rods are larger than the radiator rod. Figure 11. Next. prepare the groundplane radials. You may need to use a wooden stick inserted into the tube to position the eye terminal exactly under the hole. Figure 11. Tighten the screw to hold the eye terminal against the wall of the tube (see Figure 11.Secure the braid by inserting a self tapping screw into the lone hole and tapping into its eye terminal inside the tube.15).14). 113 . Each rod must be 28 inches long and threaded at one end (see Figure 11.14 Securing the braid inside the tube with a metal screw. Cut three lengths of 3/16" diameter brass rods.15 Cutting the radials and threading one of their ends.
114 . Mount the antenna to the mast by using a metal plate adaptor similar to one described in the preceeding chapters (see following illustration).16 Mounting the WA-2 to the mast.Final assembly and installation Attach the three groundplane radials into their mounting holes at the aluminum bushing. Figure 11.
17 Preparing the antenna for tuning to resonance.17).Tuning WA-2 to resonance Mount the antenna to the mast as previously described. Figure 11. Attach also a short coaxial feeder into the input of the SWR meter (usually marked 'transmitter') and the other end of the feeder must be plugged into the output connector of your transceiver (see Figure 11. Connect a coaxial cable into the PL-258 connector of the antenna and attach the other end into the output of an SWR meter (marked with 'antenna'). 115 .
19).Set your transceiver's frequency to the center of the band and key the PTT. Read the SWR response and write it down to a chart similar to the one shown in Figure 11.18. 116 . Resolder the hook-up wire to another point in the copper coil to get the lowest SWR response in the center frequency and a relatively flat response over the entire band similar to the charted response shown below (see Figure 11.18 SWR chart. Figure 11.19 A sample of a charted SWR response. Figure 11.
left or right . solder the hook-up wire permanently (see Figure 11.20). Move the tap only about 1/4 inch farther each time. You must check the SWR reading over the entire band everytime you move the tap.to the left.You can move the soldered point or tap either way .depending on how the SWR responses. After you have found the best point in the copper coil. 117 .20 Resoldering the tap to a different point to find the best SWR response. If you have moved the tap to the right and the SWR went higher then obviously you must move the tap to opposite direction . Figure 11.
Place the heat shrinking tube into the antenna wrapping the entire coil form and heat it over a flame or with a blow drier.Dismount the antenna from the mast and remove its three groundplane radials. Figure 11. don't let the flame touch the tube directly. The coil form and shrinking tube must be rotated continously over the heat to result to an even shrinking of the tube (see Figure 11. If you are heating the tube over the flame.20).21 Heating the shrinkable tube. 118 .
However. This current is negligible in the HF frequencies but must not be ignored in VHF or UHF frequencies.it detunes the system for stray currents present on the ouside of the line. 119 . Why is this so?. This problem is remedied by the metal cones described in this particular model . Stated simply. The overall result is that current will flow on the outside of the outer conductor. if a coaxial cable is used to feed the antenna. it has two metallic cones attached to a long tube which doubles as support for the radiator element. let us first go back to some basics to understand this phenomenon. In a perfectly balanced antenna the electrical current within each leg of the element is symmetrical. As can be clearly seen in the following illustration. the coupling action is inherently unbalanced because of the physical construction of the coaxial cable. Its function is to nullify the unbalanced coupling between the transmission and the antenna feedpoint and prevent the unwanted current from flowing on the outside of the coaxial cable.12 Model WD-2 5/8 WAVE ANTENNA This antenna is an improvement of the basic design of 5/8 wave vertical with radials. There will be no problem in coupling the RF signal to its feedpoint when a balanced feedline is used. The cones are not intended for novelty but serves a very important purpose for a more efficient performance of the entire antenna system. The cones are also called " detuning sleeves" or "decoupling sleeves". Well. the outside part of the outer conductor is not coupled to the antenna in the same way as its inner part is coupled to the inner conductor.
Desense and feedback is avoided by using high-Q cavitly filters inserted in the transmission line for the transmitter or receiver antenna or both. The difference between the two models is that the mounting tube for the model WD-2 is 104 inches long and has no groundplane radials but instead it has two decoupling sleeves made of metal cones attached to the lower portion of the mounting tube. Although the frequency of the transmitter unit is different from the frequency of the receiver unit.8 dB compared to a standard dipole reference. Using a decoupled antenna system such as the one described in this chapter will save you from the trouble. The radiation pattern is omni-directional.An antenna system with a properly decoupled line is commonly used in repeater systems because by the very nature of its design. It has a gain of 1. The model WD-2 is specifically dimensioned to operate in the 140-150 MHz band. A repeater station has both receiver and transmitter units simultaneously operating when used.5:1 over the entire band. It exhibits an SWR response of less than 1. Feedback also results to loud squeal heard by the users. Additionally. The entire system ceases to function as a repeater then. a repeater station is very sensitive to any kind of stray RF signal. the automatic switching electronics of the repeater is also protected against picking up unwanted RF by enclosing it in a metal box and by extensive use of decoupling circuits in all the leads going in and out of the box. the very close proximity of the two units tends to blank out the generally weak signals from distant stations. 120 . However all of these efforts could fail if the stray current that travels along the outside part of the transmission line is so strong that it penetrates all filters installed in the repeater system. This results to a phenomenon called "desensitation" or "desense" where the repeater cannot receive the signals from the user stations. Materials needed This antenna is basically the same with the antenna model WA-2.
Figure 12. overlap its edges and drill holes along the edge. Cut the cone form from a metal plate (GI sheet or aluminum) following the dimensions shown in Figure 12.Construction Construct the antenna following the procedures described for the model WA-2 in chapter 11 except for the length of the mounting tube which is 104 inches long for the model WD-2. In forming the cone.2 Fabricating the decoupling sleeve (or 'decoupling skirt'). construct the decoupling sleeves and attach them to the mounting tube following the procedures described here. Furthermore. Rivet the ovelapping edges through these holes.2. 121 . you don't need them for this antenna anyway. Also skip the procedure for preparing the groundplane radials. before you tune the antenna to resonance.
3).4 Soldering the ring to the cone. If you use an aluminum plate you must electrically weld the two pieces together using a special welding technique with protective gas. 122 . Figure 12.3 Preparing the metal ring. This ring will serve as a mounting sleeve so that the decoupling sleeve or skirt can be securely clamped to the mounting tube (see Figure 12. Figure 12. Solder the ring to the apex of the cone (see Figure 12.Cut a narrow strip out of a similar material and form it to a ring with a diameter of 1 inch as shown. Leave a small gap between the two ends.4).
6). Place a tube clamp over each cone and tighten it to secure the cones firmly to the mounting tube (see Figure 12.Attach the two decoupling sleeves/skirts into the mounting tube following the distances shown in Figure 12. Figure 12. 123 .5.5 Mounting the decoupling sleeves to the antenna.
124 .Figure 12. Tuning the antenna to resonance The tuning procedure for this antenna is the same with the procedure for tuning the antenna model WA-2.6 Securing the cone to the mounting tube with a hose clamp. Just follow the procedures described in chapter 11.
7 Mounting the WD-2 to the mast. 125 .INSTALLATION Figure 12.
portable transceivers in general have low power transmitters because of obvious limitations in the type of batteries practically allowable for mobile operations. However. sensitivity. The average transmitting power of handheld units range from 0. Because of this.1 5/8 wave antenna model PF-2C. 126 .13 5/8 WAVE ANTENNA Model PF-2C Most mobile operators use portable handheld transceivers because these are lightweight and small. PLL stability and many other unique features. computerized funtions. most antennas used for portable sets are of gain type to increase the effective radiated power.5 watts to 5 watts maximum. Figure 13. There are also available models today that equal the capabilities of their base station versions in terms of frequency coverage.
The telescopic element may be used while retracted or collapsed and will function like an ordinary "rubber ducky" antenna that comes as a standard accessory for portable transceivers. Furthermore an invaluable knowledge can be gained during the actual construction of this antenna.The antenna described here is a portable version of a 5/8 wave vertical antenna. 26 or approx. 1 1 1 1 1 4" long 5/8" or 3/4" od* x 4" long Miscellaneous: Epoxy glue • od . Gain can only be realized if the antenna is used while the radiator is extended to full length. The materials used for this model can be bought cheap and constructing it can save a lot of money. The antenna is then mounted high up in a post or tower.outside diameter 127 .approx. The total cost of the antenna is a mere fraction of the price of its commercial version. It is loaded at the base by a coil that doubles as a flexible spring supporting the telescopic rod. It exhibits an SWR of less than 1. an antenna of this length has a slight gain over a dipole. The radiator element of this model is made of telescopic rod so that the overall length of the antenna can be reduced if desired. This can be accomplished by using a length of coaxial cable to connect the antenna to the transceiver. Sometimes it is desirable to raise the height of the antenna to increase its effective range. a gain of 1. This particular model is dimensioned to operate in the frequency band of 140-150 MHz. Tuning is easy as described in this chapter. 22 stranded Heat shrinkable tube Dimensions 46" fully extended 6" to 7" retracted 24" or 60 cm. Installing the antenna to a higher position clears it from most obstructions such as houses or trees and extends the horizon farther away thereby increasing the area covered or "seen" by the antenna. Materials List Quantity 1 Specification/Description Telescopic antenna . It can also be hung under a tree by using a non-metallic material such as nylon or fishline. Approximately.5:1 over the entire band if properly tuned. 7/16" od* of the base tube Brass wire no.8 dB can be attained with this type of antenna. As stated earlier. 3/32" diameter BNC VHF male connector 10 pF/150 Volts capacitor glass type Hook-up wire no.
Figure 13. 128 .2).Construction Wind the brass wire into a spring like coil form. The inside diameter of the coil spring must be force fit to the outside diameter of the BNC connector or approximately 3/8" id*. *id-inside diameter Solder about 2" long hook-up wire to the center pin of the BNC connector. The total length of the finished coil is approximately 3 inches (see Figure 13. Figure 13.3 Soldering the hook-up wire to the center pin of BNC.2 Constructing the spring coil. Wind 13 turns of the wire with a pitch of approximately 4 turns per inch.
4 Fixing the center pin to the BNC connector with epoxy glue.Place a moderate amount of epoxy glue around the soldered part of the needle. Let the epoxy cure and harden.5). 129 . Solder the part of the coil that wraps around the body of the BNC connector (see Figure 13.5 Assembling the BNC connector and the spring coil together. Figure 13. When the epoxy hardens insert the BNC connector into one end of the spring coil. Insert the needle into the BNC connector and cover the empty space inside with a liberal amount of epoxy (see Figure 13.4). Figure 13. Avoid coating the epoxy around the body of the center pin.
7). Figure 13.6). Figure 13.8.7 Soldering one lead of the capacitor to the grounded portion.Pry out the free end of the hook-up wire inside the coil spring and solder it to the point of the coil which is 1 and 1/2 turns counting from the ungrounded portion of the coil (see Figure 13. solder the upper lead of the capacitor to the 6th turn of the coil spring counting from the ungrounded portion. Insert the 10 pF capacitor inside the spring coil and solder its lower lead to the grounded portion of the coil (see Figure 13.6 Soldering the hook-up wire to a temporary tap point. Figure 13. 130 .8 Soldering the upper lead of the capacitor. Next. See Figure 13.
it only needs to be tuned to resonance for proper operation. Figure 13. At this point the construction of the antenna is already finished. 131 .9). Let 2 turns of the coil hold the base of the antenna and solder it to secure the two pieces together (see Figure 13.9 Final assembly of the antenna.Next step is to insert the base of the telescopic antenna into the open end of the coil spring.
10). 132 . Similarly.10 Preparing the PF-2C for resonance tuning. connect the SWR meter to the transceiver using a short length of coaxial cable (see Figure 13. Figure 13.Tuning the antenna to resonance Attach the antenna directly to the output connector of the SWR meter using the necessary adaptors.
Read all the SWR responses from the lowest frequency up to the highest frequency in the band and mark all the results on the chart until you get a response curve similar to the one shown in Figure 13.12 A sample of an SWR curve. 133 . Figure 13.12.11.11 A sample chart for SWR readings.Set the transceiver to the center frequency and key the PTT. Figure 13. Read the SWR response and note it on a chart similar to the one shown in Figure 13.
13 Resoldering the capacitor's lead to find the right tap. If you have moved the tap to the right and the SWR went up then obviously you must move the tap to the left.5 at extreme ends of the band similar to the response curve shown in Figure 13.1 at the center frequency and 1.Resolder the capacitor's lead to a different point or tap either to the left or right of the original tap.14.13). 134 . Repeat the whole process until you find the point in the coil that results to a very low SWR reading on the center frequency and relatively balanced responses on the extreme ends of the band. it is possible to get an SWR response of 1. Key again the PTT and mark the SWR responses once again on the chart. Move the tap about 1/8" farther at a time (see Figure 13. Figure 13. If you have followed the instructions in constructing this antenna carefully.
solder it to the coil spring permanently. 135 .15).Figure 13. Figure 13.14 A sample of a good SWR response. Rotate the antenna and the tube continously while being heated to get an even shrinking of the tube (see Figure 13. After you have found the right tap.15 Heating the shrinkable tube. Insert the spring coil into the heat shrinkable tube and heat the tube over a flame or with a blow drier.
A collinear array is a broadside radiator. It has two identical dipoles fed with a coaxial phasing line or 'harness'. 136 . this type of antenna is limited to fixed installation only because of its mechanical construction. The dipole elements are always driven in phase otherwise the array simply becomes a harmonic type antenna. meaning the direction of maximum radiation is at right angles to the line of the antenna.5:1 over the entire band. It has an SWR response of less than 1. In fact. One advantage of this design is its ability to attain high gain. it is the same design of dipole just 'doubled' and fed simultaneously. Each dipole element is tuned by a gamma matching system similar to that described in chapter 6. Tuning procedure is similar to that described for dipole model DP-2.14 COLLINEAR ANTENNA Model SD-22 (2 stacked dipole) A collinear antenna is made up of a multiple number of dipoles mounted in a common structure with their axis arranged in one straight line. This configuration gives a gain of 3 dB compared to a single dipole. When dipole elements are stacked collinearly. Obviously. This model is dimensioned to operate in the frequencies of 140-150 MHz band. An actual working design of a collinear array is presented here. it radiates an omni-directional pattern. When mounted vertically. the power gain increases in direct proportion to the number of dipoles used.
2 pcs.1/2" clamping capacity 6 pcs. The mounting channel for model SD-22 is slightly different and is described in the following illustration (see Figure 14. 2 pcs. Additionally. In short the additional materials needed for SD-22 are as follows: Quantity 2 pcs. BNC VHF male connector BNC 'T' connector Construction Follow the procedures for constructing the dipole antenna model DP-2 and make two identical dipoles. 1 pc. Description Square aluminum channel Square aluminum channel Hose clamp Dimensions 1" x 1" x 8" 1" x 1" x 115" 2 . Also. The mounting channel for SD-22 is shorter being only 8 inches long and has slits on two sides instead of two holes.Materials needed Most of the materials needed to build the antenna model SD-22 are the same with those needed for antenna model DP-2 except for the mounting channel. 137 .2). another long square channel is needed to mount the two dipole elements into a single mast. a system of phasing harness made of coax cable is required to feed the two dipoles simultaneously.
A hose clamp will be inserted into these slits for the purpose of mounting the channel to the supporting mast (see Figure 14.Figure 14. Saw shallow slits at two sides of the channel using a hacksaw. 138 .2 Mounting channel dimensions.3 Saw slits at two sides of the channel.3). Figure 14.
Figure 14. Wrap the two hose clamps around the body of square channel mast and tighten the clamps to hold the dipole elements rigidly.5. insert the hose clamps through the slits in the channel (see Figure 14. 139 .5 Mounting the dipoles to the aluminum mast.4). Figure 14. After the dipoles are completed.Assemble the two dipole elements following the procedures described for antenna model DP-2.4 Assembled dipole element with hose clamp. Mount the two dipoles to the aluminum supporting mast following the dimensions shown in Figure 14.
The antenna must be elevated to not less than 1 meter above the ground supported by non-metallic materials like wooden benches for example. construct the phasing harness using RG-58/U coaxial cables and the appropriate connectors (see Figure 14. 140 . Finally connect the phasing harness to the two dipole elements and secure it to the support mast with plastic binders (see Figure 14. Tuning the antenna The tuning procedure for the antenna model SD-22 is similar to the procedure for tuning the antenna model DP-2. then it can be tuned on the ground by placing it in a horizontal position with the dipoles facing upward. You have to do a lot of shuttling back and forth between the two dipoles before you can achieve a good match. Figure 14.6 Constructing the phasing harness. If it is not practical to tune the antenna right in the main mast.7 Connecting the phasing harness to the antenna.Next. In tuning the SD-22 however. the two dipoles have to be tuned simultaneously.7).6). Figure 14.
the number of dipole elements installed cannot be simply dictated by personal choice.meaning.15 STACKED DIPOLE ARRAY Model SD-24 (four stacked dipole) This model demonstrates the capability of a simple dipole to attain high power gain by simply stacking identical units into a single structure and feeding them all simultaneously with a phasing harness. it the original array has two dipole elements installed. power gain in a collinear array increases in direct proportion to the number of dipole elements used. Everytime the number of dipole elements used is doubled. This arrangement is also called collinear array. As stated earlier in chapter 14. The correct method is to double the original number of dipole units . However. then the next array must have four dipoles and the next must have eight dipoles and so on. 141 . the power ratio is also doubled. in order to construct a practical phasing harness.
The square channel used to mount the four dipoles is larger and twice longer than the one used for SD22. A collinear array having eight dipole elements will have a power gain of 9 dB. Materials List The necessary materials in building this antenna are the same with those needed for SD-22 being its extended version. this array exhibits an SWR of less then 1. If properly tuned. The procedure for tuning this antenna to resonance is similar to the procedure for model SD-22.Ü NOTE: The power ratio is not numerically the same with the dB figure. An array with elements in excess of eight is rarely constructed because of the inherent mechanical problems encountered in erecting structures of this size. 4 pcs. For accurate computations refer to Appendix. Additional materials for Model SD-24 are as follows: 1 pc. The model SD-24 is specifically dimensioned to operate in the frequencies of 140-150 MHz band. 2 pcs. Most collinear antennas are mounted vertically to effect an omni-directional pattern of radiation. Square aluminum channel BNC male connectors BNC 'T' connectors 1-1/2" x 1-1/2" x 235" 142 . Additional set of phasing harness is also needed to feed the four dipole elements simultaneously. The particular four-element array presented here has a power gain of 6 dB.5:1 over the entire band.
3). Mount the four dipoles to the aluminum supporting channel by using hose clamps. Tuning SD-24 to resonance Tuning the antenna model SD-24 to get a good match is similar to procedures for tuning antenna model SD-22.2 Mounting the four dipole elements on the mast. The antenna elements must be attached to the mast with the proper distances from each other (see Figure 15. 143 .Construction Construct the four dipoles following the procedures described for models DP-2 and SD-22. Figure 15. Figure 15.2).3 Constructing the phasing harness. Construct the phasing harness as shown and attach it to the four dipoles in similar fashion to model SD-22 antenna (see Figure 15.
the high gain character of a yagi becomes useless unless the antenna is intended to be permanently beamed to a single direction such as in the case of fixed point-to-point communication. A basic hafwave dipole is cut to resonance at the center of the frequency band and is utilized as the driven element. their diameter. 144 . These parasitic elements are called directors and reflectors depending on their length and positioning with respect to the drive element. The reflector is longer by approximately 5 % and is positioned behind the driven element. The director on the other hand is cut shorter by approximately 5% and is positioned at the front of the driven element. Among these are the number of elements used. the radiation pattern becomes uni-directional and the much desired omni-pattern is completely lost. Maximum radiation of signal is now concentrated at the front of the antenna and there is only minimum radiation at the back. This highly directive and uni-directional characteristics of a yagi antenna necessitates the use of a rotator device in order to beam it to the direction of the station in contact. It was named after the two Japanese physicists who invented it. The basic yagi is one of the highest gain antennas yet developed. The combination of these elements produce the directivity of the radiated signal thus resulting to higher power gain. However. The ratio between the radiated signal at the front and the radiated signal behind it is called 'front to back ratio'. and the spacing between them. High gain is attained by the addition of parasitic elements positioned either in front or behind the driven element. If a rotator device is not used. The ratio between the radiated signal at the front and the radiated signal at the sides is called 'front to side ratio'.16 YAGI-UDA ANTENNA Model YG-23 (3 element beam) A yagi-uda antenna is a type of an array having one active dipole and two or more parasitic elements. Radiation is weakest at the sides of the yagi and these points are called 'null points'. Several factors affect the performance of a Yagi.
It has a gain of approximately 7.3 dB compared to a standard dipole reference.The dimension of model YG-23 is specially cut to resonate in the frequency band of 140-150 MHz. Detailed information for the exact dimensions of additional director elements and their spacing is given in chapter 17.1 Yagi antenna model YG-23 145 . These yagi dimensions are based on the information published by the National Bureau of Standards.5:1 over the entire band. If properly tuned. Scaled down Appearance Figure 16. This is only a basic configuration of a yagi and its gain and directivity can be increased by adding more directors at the front. it exhibits an SWR of less than 1.
Materials List Quantity 1 1 1 1 Specification/Description Aluminum tube 3/8" od* Aluminum tube 3/8" od* Aluminum tube 3/8" od* Aluminum square channel Dimensions 3 feet 4" 3 feet 2-3/16" 3 feet 7/8" 1" x 1" x 2 feet and 32-1/4" Other materials used in constructing the antenna DP-2 are also needed for this yagi antenna except for the mounting channel. 146 .2). The shortest tube will be used as a director element. * od . the longest tube will the reflector element and the medium length will be the driven element (see Figure 16.outside diameter Construction Cut the three tubes to their exact lengths and drill a hole (1/8" diameter) thru and thru at its middle length. Figure 16.2 Preparing the reflector element.
Cut the aluminum mounting tube or boom to 2 feet and 11 inches long and drill three holes thru and thru at one side. Drill also three 3/8" diameter holes at the same point where the larger holes are but at one side. The axis of the smaller holes must cross the axis of the larger holes (see Figure 16. The holes must have a diameter of 3/8" or enough to accomodate the diameter of the tube that will be inserted into it.3 Preparing the driven and director elements. 147 .4 Preparing the boom. Figure 16.4). Follow the dimensions shown.Figure 16.
6 Complete assembly of the driven element. clamp. bracket.g. All other materials and dimensions (e.) are similar to those used for the dipole elements of DP-2 (see Figure 16. gamma. Secure the tube to the boom by placing the screws through the holes at the sides similar to the method of attaching the dipole element of the antenna model DP-2 (see Figure 16. Complete the attachments of the driven element following the procedures described for model DP-2.Insert the aluminum tubes to the boom following the illustration for the proper arrangement of the elements.5). etc. connector. Figure 16.6). 148 . Figure 16.5 Assembling the antenna elements to the boom.
149 .Installation of YG-23 Figure 16. SD-22 or SD-24.7 Installing the YG-23 to the mast. Tuning YG-23 to resonance The tuning procedure for the antenna model YG-23 is similar to the procedure for tuning antennas model DP-2. The most important instruction to keep in mind is to tune the antenna while directly attached to the mast where it will be permanently installed whenever practical.
director elements. The latter is widely popular among the antenna constructors because it is easier to construct and eliminates the need for individual insulators. gamma match. assembly of the whole antenna and tuning procedures are basically the same with the model YG-23. The construction of the reflector. The following table shows the exact element lengths and dimensions for various yagi antennas based on the NBS standard. you can achieve a very high gain figure from this type of antenna. one set for the type of yagi antenna with elements that are insulated from the boom and another set for the yagi antenna with elements directly attached to the metal boom. By adding more director elements at the front and extending the boom length of the yagi. Two sets of dimensions are given. 150 .17 MULTI-ELEMENT YAGI-UDA ANTENNA ARRAY The Yagi-Uda antenna or simply 'yagi' model YG-23 described in the preceeding chapter gives a fairly high gain figure in a very compact and easy to construct antenna. driven element.
1 Dir.2λ) λ 21'10-1/16"(3.2λ) λ 1" 1" 3/8" od* 3/8" od* YES NO YES NO YES YES NO YES NO 3'4" 3'4-5/8" 3'4" 3'4-5/8" 3'4" 3'4" 3'5-1/16" 3'3-3/8" 3'4-1/2" 3'2-3/16" -do-do-do-do-do-do-do-doDir.2λ) λ 28'8-1/8" (4. 15 2'10-9/16" 2'10-9/16" 2'10-9/16" 2'11-1/4" 2'11-13/16" 2'11-3/8" 2'11-3/8" 2'11-3/8" 3' 3'5/8" 2'10-9/16" 2'10-5/16" 2'10-5/16" 2'10-5/16" 2'10-5/16" 2'10-5/16" 2'10-5/16" 2'10-5/16" 2'10-5/16" 2'10-5/16" 2'11-5/8" 2'11-3/8" 2'11-3/8" 2'11-3/8" 2'11-3/8" 2'11-3/8" 2'11-3/8" 2'11-3/8" 2'11-3/8" 2'11-3/8" 2'11-1/8" 2'10-13/16" 2'10-9/16" 2'10-9/16" 2'10-9/16" 2'10-9/16" 2'10-9/16" 2'10-9/16" 3'3/16" 2'11-7/8" 2'11-5/8" 2'11-5/8" 2'11-5/8" 2'11-5/8" 2'11-5/8" 2'11-5/8" * od .2 Dir. 14 Dir. 13 Dir.8λ) λ 8'2-5/16" (1.3 Dir.2λ) λ 1-1/2" 3/8" od* 1-1/2" 3/8" od* 1-1/2" 3/8" od* 3''7/8" 3'1-1/2" 3' 7/8" 3'1-1/2" 3'1-1/8" 3'7/8" 3'1-15/16" 3'9/16" 3'1-5/8" 3'11/16" 3'1-3/8" 3'7/16" 3'1-1/8" 3'5/16" 3'9/16" 3'1-3/8" 3'9/16" 3'1-5/8" 3' 7/8" 3'1-1/2" 3'7/16" 3'1-1/8" 2'11-13/16" 2'11-3/4" 3'13/16" 3'3/8" 3'1-7/16" 3'7/8" 3'1-1/8" 2'11-1/4" 2'11-1/8" 3'3/16" 2'11-5/8" 3'11/16" 2'10-9/16" 2'10-7/8" 3' 2'11-1/2" 3'9/16" Dir. 8 Dir.5 15'1/4" (2. 7 Dir. 9 Dir. 10 Dir. 11 Dir.4 Dir. 12 Dir. 6 Dir.NBS YAGI STANDARD DIMENSIONS Boom Length Boom Element Insulated Reflector Driven Diameter Diameter Elements 5'5-9/16" (0.outside diameter 151 .
152 .ELEMENT SPACING WITH RESPECT TO BOOM LENGTH Figure 17.1 Element spacing of a Yagi antenna with respect to its boom length.
Similarly.2). a 17-element yagi with a gain of 13. The distance between the tips of the elements in vertically stacked yagis must not be less than one-half wavelength or it must be approximately 38 inches (see Figures 18.1 2 stacked yagis viewed at their boom ends. the spacing between the antennas is important. If a number of the yagi antennas is doubled.3 dB.3 dB. The distance between two yagis stacked side by side must not be less than 1 wavelength or it must be approximately 77 inches.1 and 18. For example.4 dB if stacked to four identical pieces! In stacking yagis. it will add an additional 3 dB to the original gain figure of the yagi.4 dB will give a whooping 19. 153 .18 STACKING YAGI ANTENNAS Stacking yagi antennas means multiplying the number of yagi antennas and feeding them all simultaneously. Figure 18. it will give you a total gain figure of 10. if you feed two identical 3-element yagi which has a gain of 7.
3 Phasing harness for a 4-stacked yagi antenna.Figure 18. For example. 154 . All the yagis must be fed in phase with a phasing harness.2 4 stacked yagis viewed at their boom ends. the configuration of a phasing harness for the 4 stacked yagis shown above is described in the following illustration. Figure 18.
5 Attachment of the cross-arm to mast.Mechanical Construction Figure 18.4 Attachment of the boom to cross-arm. 155 . Figure 18.
The formula to get the electrical wavelength of a frequency is: In feet: 936 __________ Fc (MHz) In meters: = λ (feet) 286 __________ = Fc (MHz) λ (meters) Ä Ä Fc is the center frequency of the band expressed in Megahertz.5)λ λ /4 or (0.46 feet or 77. the wavelength of 145 MHz is: 936 145 . The electical wavelength of a certain frequency is slightly different from its wavelength in free space.FORMULAS FOR CONVERTING 19 ANTENNA DESIGNS FOR OTHER FREQUENCY BANDS The dimensions of the antenna elements are generally derived from the antenna's electrical wavelength. n For example. Lambda λ is the symbol for the wavelength expressed either in feet or meters depending on the particular units used.52 inches Other symbols of wavelength: λ /2 or (0. = 6.25)λ = halfwavelength = quarterwavelength 156 . where the former is the wavelength of the signal present in the physical conductor of the antenna and is somewhat shorter.
72 12. n Example: Find the length of one groundplane element intended for 220 MHz.25 λ E (feet) = or n To convert E (feet) to inches multiply it with 12.Groundplane elements The formula to get the length of each element of a groundplane antenna is: 468 Fc 2 E (feet) = 0.127 2 1. Solution: E (feet) = 468 220 2 2.72 inches ß this is the length of the element expressed in inches 157 .06 x 12 = E = 12.06 substituting the value of frequency E (feet) = E (feet) = ß this is the length of the element expressed in feet To convert the result to inches: E (feet) x 12 = E (inches) 1.
Solution: E (feet) = 468 Fc 2 468 E (feet) = 110 2 E = 2.5 inches ß 158 this is the final value expressed in inches .5 E = 25.125 feet substituting the value of frequency ß this is the length of the coaxial element expressed in feet Convert the result to inches: E (feet) x 12 = E (inches) 2.125 x 12 = 25.Coaxial dipole elements Formulas to find the elements of a coaxial dipole: 468 E (feet) = Fc 2 E (feet) = 0.25 λ or n Example: Find the length of the element for a coaxial dipole intended for 110 MHz (also known as aircraft band).
12 inches ß this is the final value expressed in inches 159 .51 x 12 = S = 18.25 λ 2 S (feet) = or S (feet) = n Example: Find the length of one side of the quad loop intended for 155 MHz (VHF commercial band).51 feet S (feet) = S (feet) = substituting the value of frequency S (feet) = S = ß this is the length of one side of the loop element expressed in feet Convert the result to inches: S (feet) x 12 = S (inches) 1. Solution: 468 Fc 2 468 155 2 3.Quad loop antenna element The formula to get the length of each side of the loop element for the Quad loop antenna: 486 Fc 0.12 18.02 2 1.
D (feet) = 468 Fc 468 195 2. SD-22.Dipole element The formula to get the length of the dipole element for the antennas DP-22. and SD-24: 486 D (feet) = Fc D (feet) = 0.8 D = 28.8 inches ß this is the final value expressed in inches 160 .4 x 12 = 28.4 feet D (feet) = D (feet) = ß this is the length of the dipole element expressed in feet Convert the result to inches: D (feet) x 12 = D (inches) 2.5 λ or n Example: Solution: Find the length of the dipole element intended for 195 MHz.
25 λ S (feet) = or n Example: Find the spacing between two dipoles designed for 220 MHz.127 2 S = 1.053 x 12 = 12. Solution: S (feet) = 468 Fc 2 468 S (feet) = 220 2 S (feet) = 2.Spacing between dipoles' ends The formula to get the correct spacing between the ends of two dipoles in a collinear array such as SD-22 or SD-24: 468 Fc 2 S (feet) = 0.053 feet ß this is the length of the dipole element expressed in feet Convert the result to inches: S (feet) x 12 = S (inches) 1.45 161 .
l The cone element length is 0.45 inches ß this is the final value expressed in inches Ü NOTE: This spacing is only for the minimum allowable between the ends of the dipole elements in a collinear antenna. Discone dimensions To get the exact lengths and dimensions of the discone antenna. λ λ.25λ and 0.0077 of the wavelength. Optimum spacing is within 0. l The spacing between the disc element and the apex of the cone element is 0.29 of the wavelength.19 of the wavelength. first compute the wavelength of the lowest targeted frequency by using this formula: λ (wavelength in feet) = 936 Fc Formulas for dimensions: l The disc element diameter is 0.5λ. 162 . l The diameter of the mounting tube is not critical. n Example: Find the dimensions of a discone antenna with a cut-off frequency of 120 MHz (upper portion of the aircraft band).S = 12.
72 7.03 10 10.000 +40 x100.76 3.19 6.68 6. Power loss in relation to the SWR figure in the transmission line: SWR 1 1.42 5.57 9.06 8.98 5.04 = 12.29 10.92 9. a power ratio of 16 which is the same as 10 x 1.22 4.80 6.31 5. including the decimal increment.98 9.91 6.6 2.8 is equivalent to 2.9 2.44 7.56 8. a power ratio of 1.45 8 9.56 6.63 9.04 dB.24 7.0 0.55 dB.91 6.14 10.2 0.02 5 6.3 1.4 1.5 1.24 10.78 7 8.20 8.00 x10 +10 x100 +20 x1000 +30 x10.08 7.30 4.40 8.99 8.1 0.41 3.29 0.79 3.44 10.13 8.85 8. For example.33 0.21 0.48 8.6 is equivalent to 10 + 2.17 0.79 4.86 9.34 10.51 9.25 0.37 1 0.55 4.14 3.5 1. Value from the table may be extended as indicated at the lower left in each section.7 2 3 4 5 6 10 :1 :1 :1 :1 :1 :1 :1 :1 :1 :1 166 Power lost in % 0 2 3 6 11 25 38 48 55 70 % % % % % % % % % % .00 2 3.46 3.92 8.49 10.23 7.32 8.62 5.08 10.33 8.7 2.26 8.90 7.000 +50 How to use this chart: The decibel value is read from the body of the table for the desired ratio.47 5.APPENDIX POWER RATIO TO DECIBEL CONVERSION Decimal Increments Ratio 0.8 2.15 5.63 7.63 8.16 7.32 6.77 4 6.04 0.34 7.39 8.71 8.19 10.81 9.01 3 4.53 7.75 9.13 7.09 0.05 6.81 7.62 5.80 5.04 4.13 0.99 6 7.3 1. For example.44 6.69 9.40 10.
094 yards 167 .54 centimeters 0.914 meter Metric to English Centimeter = Meter = Meter = Meter = 0. If the constructor wants to use the metric system.28 feet 1.305 meter 0. he can convert all the dimensions by using the following conversion guide: English to Metric Inch Inch Foot Yard = = = = 25.3937 inches 39.METRIC EQUIVALENTS Most of the antenna dimensions described in this book are in English units.37 inches 3.4 millimeters 2.
Commonly used at medium frequency and high frequency to provide an effective ground for an antenna. The group of frequencies where the antenna functions efficiently. A linear array of radiating elements (usually dipoles) with their axis arranged in a straight line. A group of frequencies. An antenna that is split exactly at the middle for connection to a feedline. The enclosed angle in degrees inside the cone element of a discone antenna and similar antennas. the condition of the soil and the geographical region. The depth of this point varies with the frequency. or solid dielectric compounds. A metal body such as tubing. Usually a halfwavelength in dimension. Any of the coaxial transmission lines that has the outer shield (either solid or braided) in the same axis as the inner or center conductor. but insulated from ground. helium. An electrical conductor or array of conductors that radiates signal energy (transmitting) or collects signal energy (receiving). The feedpoint region of a discone antenna. such as found in insulators and transmission lines.GLOSSARY OF ANTENNA TERMS Actual ground The point within the earth's surface where effective ground conductivity exists. to form a low impedance. high capacitance path to ground. rod or wires that permits current to travel continously along its length. A wire or group of wires mounted close to ground. Antenna Apex Apex angle Bandwidth Band Coaxial cable Collinear array Conductor Counterpoise Dielectrics Dipole 168 . The insulating material can be air. Popular in VHF and higher frequencies. Also called a doublet. Various insulating materials used in antenna systems.
169 Direct ray Doublet Driven array Driven element Efficiency Feeders Feedline Front to back Front to side Gain Gamma match Groundplane Groundscreen . A dipole would have a ratio of 1 for example. Increase in effective radiated power in the desired direction of the major lobe. A matching system used with driven antenna elements to effect a match between the transmission line and the feedpoint of the antenna. determined in antenna systems by losses in the system. The element to which the transmission line is connected. ground or man made reflector. A wire mesh groundplane. including in nearby objects. Transmission lines of assorted type that are used to route RF power from a transmitter to an antenna. Frequently used singly or in multiples with Yagi or cubical quad beam antennas. It consists of an adjustable arm that is mounted close to the driven element and in parallel with it near the feedpoint. A man made system of conductors placed below an antenna to serve as an earth ground. The radiator element of an antenna system. Transmitted signal energy that arrives at the receiving antenna directly rather than being reflected from the ionosphere. The ratio of useful output power to input power. see Feeders The ratio of radiated power off the front to the back of a directive antenna.Directivity Director The property of an antenna that concentrates the radiated energy to form one or more major lobes. The ratio of radiated power between the major lobe and the null side of a directive antenna. or from an antenna to a receiver. see Dipole An array of antenna elements which are all driven or excited by means of a transmission line. A conductor placed in front of a driven element to cause directivity.
The antenna is a load for a transmitter. Most often used with a parasitic loop director and a parasitic loop 170 Lambda Line loss Line of sight Load Loading Lobe Matching Null Parasitic array Phasing lines Quad . Sections of transmission line that are used to ensure correct phase relationship between the bays of an array of antenna. Also used to effect impedance transformations while maintaining the desired array phase. Maximum power transfer to the load (antenna system) will occur when a matched condition exists. The power lost in a transmission line. Rectangular or diamond shaped fullwave loop antenna. A condition during which an electrical property is at minimum. The process of effecting an impedance match between two electrical circuits of unlike impedance. matching section or a transmission line. The electrical entity to which the power is delivered. The process of transferring power from its source to a load. The null in an antenna radiation pattern is that point in the 360 degree pattern where minimum field intensity is observed. An impedance bridge is said to be 'nulled' when it has been brought into balance. A yagi antenna is one example. usually expressed in decibels. A dummy load is a nonradiating substitute for an antenna. One example is matching a transmission line to the feedpoint of an antenna. The directors and reflectors are not connected to the feedline. See also driven array. Transmission path of a wave that travels directly from the transmitting antenna to the receiving antenna. A directive antenna that has a driven element and independent directors or reflectors or both. A defined field of energy that radiates from a directive antenna. An impedance may contain reactance as well as resistance components. Greek symbol for L used to represent a wavelength with reference to electrical dimensions in antenna work.Impedance The ohmic value of an antenna feedpoint. The effect of a load has on a power source.
See SWR. Radiation pattern The radiation characteristics of an antenna as a function of space coordinates. Large man made structures may reflect radio signals. A VSWR of 1:1 occurs when all parts of the antenna system are matched correctly to one another. A factor of 1 is applied to the speed of light and radio waves in free space. Often called the 'cubical quad'. When cutting a transmission line to a specific electrical wavelength. Standing wave ratio on a transmission line in an antenna system. A continous surface that is the locus of points having the same phase at the same instant. A disturbance that is a function of time or space or both. The ratio of the forward to reflected voltage on the line and not the power ratio. Radiator A discrete conductor in an antenna system that radiates RF energy. A parasitic antenna element or a metal assembly that is located behind the driven element to enhance forward directivity. That which affects the speed of radio waves in accordance to the dielectric medium they are in. Normally. but the velocity is reduced in various dielectric mediums such as transmission lines. The point of origination (transmitter or generator) of RF power supplied to an antenna system. The process of placing similar directive antennas atop or beside one another forming a 'stacked array'.reflector to provide approximately 8 dB of gain and good directivity. 'VSWR' or voltage standing wave ratio. the velocity factor of the particular line must be taken into account. More correctly. the pattern is measured in the far field region and is represented graphically. The element to which the feedline is attached. A radio wave for example. Voltage standing wave ratio. Reflector Source Stacking SWR Velocity factor VSWR Wave Wave front 171 .
Radio Engineering. 1966 172 . The ARRL Antenna Book. chap. The ARRL Handbook. I. Radio Antenna Engineering . July 1957 Rumsey.. P.E. BIBLIOGRAPHY Source materials for more advanced study of the antenna designs presented in this book can be found in the following references: Lytel.R. QST. I. 13 Reynolds. "Circuit Relations in Radiating Systems and Applications to Antenna Problems". "The Element Spacing in 3-element Beams". May 1963 Brown. Antenna (New York: Mcgraw Hill Book Co. Proc. June 1937 Carter. January 1937 Brown. QST. The ARRL Antenna Book. QST.L. Antenna Engineering Handbook (New York: Mcgraw Hill Book Co. 1952 "Omni-directional Antennas For VHF and UHF". I. Lewis... 1973 "Antenna Fundamentals".. 14th ed. Frequency Independent Antennas. New York: Academic Press. chap.2 Jasik.a VHF-UHF Tribander". "Simple Gamma Match Construction". gain type of antenna that utilizes a number of parasitic directors and a reflector. Proc. December 1978 Erhorn.C.2 Bergren.. Allan.. Proc. 14th ed. New York: Mcgraw Hill Book Co. F. Dave.R. ABC's of Antennas. "Directional Antennas". and Epstein.) Laport. 1966 Terman.Yagi A directive.E. chap. 'The Multi-element Quad". Named after one of the inventors (Yagi and Uda).. chap. 11 "Portable and Mobile Antennas". October 1957 "Groundplane Antenna". 14th ed.E. A. "Ground Systems as a Factor in Antenna Efficiency". New York: Academic Press.) Kraus.. June 1932 Geiser. The ARRL Antenna Book. QST.R. 14th ed. "The Discone .
Vhf Handbook Iaru v542
1994 - ARRL Uhf Microwave Projects Vol1
AntennaDesign Proposal

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