Re: {Collins} R388 TR Relay

FWIW, I also checked for residual signal with the power switch in standby but the mute off. Nothing. I think the antenna part of the mute relay is to protect the input of the receiver in case something is connected wrong. I suppose its possible that these receivers were sometimes used with antennas separate from the transmitter and no T-R relay. The input signal I used from the GDO is extremely strong so I think I would have heard it if there was any leakage at all. About diversity work: Some 51J series receivers have the necessary connections for diversity but many do not. Diversity requires that there be an external connection to the detector diode so that the two or three receivers can be connected to a common diode load. Usually the AVC is also brought out. The simplest type of diversity system uses the output voltage from the diode getting the strongest signal to reverse bias the others. The transition is fairly sharp. Combining the AVC tends to keep all receivers operating in their linear ranges. Some more elaborate combiners use the IF output. Receivers used for more modern diversity reception generally have some means of operating the local oscillators and BFO (when used) from an external source.

Richard Knoppow
Los Angeles

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