PRC-77 Squelch Issue

[graffspee]

I have a PRC-77 that transmits and receives fine when it is in the "ON" position but when you put it in "SQUELCH" it will transmit but will not receive. I have replaced the Squelch module and tried troubleshooting using the Maintenance manual but so far I have not been able to narrow down where the issue lies. Anyone have an idea what may be causeing this issue?

 

[m38inmaine]

In order for the squelch to "open" the radio has to receive and decode a 150Hz tone. Either your radio's tone decoder is off frequency or not working or the other radio is not transmitting the tone or the tone it is transmitting is off frequency.

 

[T. Highway]

Are you using another Mil radio that is transmitting the 150Hz Squelch Signal, to talk back to the PRC-77?

Bert

I guess that you type way faster than me m38inmaine.

 

[graffspee]

Are you using another Mil radio that is transmitting the 150Hz Squelch Signal, to talk back to the PRC-77?

Bert

I guess that you type way faster than me m38inmaine.

Thanks for the reply... I have tested it with several different known working radios so I am sure that the issue is with mine. So going with what is being said the issue would likely be with the 150Hz. signal in my radio. My test equipment is limited. Would be easier if I had a working Oscilloscope but I get by. When I first got this unit id dint work at all. It looked like it fell of the back of a tank. I have been able to restore it to working order with the only remaining issue is with the squelch but now I have a little bit of a better idea of what might be going on....

 

[papakb]

In receive mode (squelch on) the A55 audio module sends the 150 hz tone back to the A54 module to open the squelch relay. You might want to pop in a different A55 and see what happens.

Kurt
KG6KMJ

 

[graffspee]

In receive mode (squelch on) the A55 audio module sends the 150 hz tone back to the A54 module to open the squelch relay. You might want to pop in a different A55 and see what happens.

Kurt
KG6KMJ

I have not tried testing the A55 module. I will try it this weekend and see what happens and post the results.....

THANKS
Mike

Here is an update. I replaced the A55 module and tested the radio. It still will not recieve in Squelch mode but transmits fine. So I am thinking the issue must be with the 150Hz. tone .

 

[Lenny]

Hi there. I just joined the group and I have a question I'd like to ask. I have a couple of PRC77's, and I would like to convert them to carrier or "noise" squelch. I have the TM and a separate schematic for the squelch module which is apparently for a Canadian version of the A24. This schematic version I have is for an A24C which I'm told is the direct replacement for the A24 in the PRC25 or the A54 in the PRC 77. Is this correct? I'm told that the A54 is what I apparently have in my radios now. If I can find two of these A24C's (or if I have to build them) will this work? Thanks, Lenny