100 percent modulated input signal voltage the grid leak detector can demodulate without excess distortion is about one half of the projected cutoff bias voltage , corresponding to a peak unmodulated carrier voltage of about one quarter of the projected cutoff bias. For power grid detection using a directly heated cathode tube, the grid leak resistor is connected between the grid and the negative end of the filament, either directly or through the RF transformer. Effect of tube type Tetrode and pentode tubes provide significantly higher grid input impedance than triodes, resulting in less loading of the circuit providing the signal to the detector. Tetrode and pentode tubes also produce significantly higher audio frequency output amplitude at small carrier input signal levels (around one volt or less) in grid leak detector applications than triodes. Advantages The grid leak detector potentially offers greater economy than use of separate diode and amplifier tubes. At small input signal levels, the circuit produces higher output amplitude than a simple diode detector. Disadvantages One potential disadvantage of the grid leak detector, primarily in non-regenerative circuits, is that of the load it can present to the preceding circuit. The radio frequency input impedance of the grid leak detector is dominated by the tube's grid input impedance, which can be on the order of 6000 ohms or less for triodes, depending on tube characteristics and signal frequency. Other disadvantages are that it can produce more distortion and is less suitable for input signal voltages over a volt or two than the plate detector or diode detector. See also Tuned radio frequency receiver Regenerative radio receiver Radio References Further reading Schematic of Philco model 84 A superheterodyne cathedral radio from 1933 that uses a regenerative detector. (Note: The capacitor for the detector's control grid is the "tickler coil" winding on the IF transformer.) Analog circuits Radio electronics Radio technology Vacuum tubes History of radio de:Gittergleichrichtung