nalogue digital examples were 32 QAM, which is used for transmitting 12kbit/s Bandwidth 10MHz 5(or 3.5) MHz data on a voice channel. Since the microwave system under con- sideration has a voice channel capacity of 600, it might be said to Voice Chan Cap have a data capacity of 12kbit/s X 600 = 7200kbit/s. However, even Max Data Cap 11.52MBit/s 2.75Mbit/s higher data rate types of data modems may operate at 19.2kbit/s. Therefore, the 600 channel microwave system might also be said to T-1 Capacity 10DS-1s 8DS-1s have a maximum data capacity of 19.2kbit/s X 600 = 11520kbit/s. System Gain 110.4dB 114.5 (or 113dB) ADS-3 digital microwave system has a capacity of just over 50/14 Line of sight radio systems capacity of only 192 vs. the 600 channel capacity of the analogue 2. No baseband slot allocation difference to consider. system. 3. Performance advantage for voice users in large systems and for For this case (similar data or T-1 capacity) the digital microwave high speed (T-1) data. system appears to be superior in terms of bandwidth usage effi- Given similar bandwidth and voice channel capacity: much ciency if primarily data or DS-1s are to be transmitted. However, if high data or T-1 capacity. primarily voice is to be transmitted, the analogue FM system has a Given similar data or T-1 capacity: much more bandwidth clear capacity advantage. efficient for data or T-1 transmission. 6. Given similar System Gain and bandwidth: higher data or T-1 50.3.6 System gain comparisons capacity. Another significant way to compare analogue microwave and digi- Advantages of analogue microwave: tal microwave systems is in terms of System Gain, i.e. the transmit- ter power to receiver sensitivity ratio in dB. Higher System Gain is 1. In small to medium sized systems: superior voice channel generally viewed as a desirable characteristic of microwave radio performance. equipment, since it is related to the ability of the system to withstand 2. For most system sizes: performance advantage for voice chan- undesirable microwave propagati