Receiver muting

[W9BHI]

I think this has been hashed over before but I don't think a working solution was ever found.
The muting scheme on my HQ-150 is very noisy (popping and thumping) when switching from RX/TX.
I was using a small relay on the rear muting terminals of the receiver with very objectionable results.
I tried using an Omron G3VM601BY solid state relay (optical FET).
It works like a champ!
No pop, and just a hint of a thump.
The device is a small 6 pin IC rated at 600 volts @100Ma. and can be had from DigiKey for $6.22.
(my Hammarlund drew 45 Ma. at the mute terminals.)
I used a 12 volt dc wallwart with an appropriate resistor to give 1.2 volts for the LED input.
The transmitter relay turned the Led on and off.
The output has a polarity so if the receiver doesn't mute, just reverse the connection on the receiver.
I am sure this can be used on other receivers as well.
Try it you'll like it!

Don W9BHI

[WQ9E]

Don,

Thanks for posting a clean and simple solution!

I am a big fan of SS relays and have used them in several amplifiers to prolong the life of the existing main power switch, in my Johnson Desk Kilowatt to replace a balky plate relay, and for the main power switching in my home brew contest amp.  They really are very versatile, inexpensive, and easy to use devices.

Two things I have found is that some of them are sensitive to RF on the relay control line which makes sense given the high impedance of this input.  I used RF chokes bypassed with capacitors on the relay in my Desk KW.  Before I added those it provided some very interesting waveforms to the primary of the plate transformer.  I found on my home brew amp that the control input needs to cleanly transition from the "ON" control value to the "OFF" control value.  A protective board I used in the amp had a slight slope between the on and off values and when the control line was in this gray zone the AC SS relays begin to act like rectifiers providing DC to the transformer and caused the breakers to open.  No damage was done and I corrected the protective circuit but this is something to keep in mind when using the AC version of these relays.

The HQ-150 is a very nice receiver and the only one I am aware of that has both a Q multiplier and crystal filter built in which should make it a very nice CW receiver in addition to AM use.