Goal: feed audio from a PC to a circuit that will trigger a relay

sghioto

Joined Dec 31, 2017
3,058
Check the audio level out from the PC at max volume without connecting to the relay circuit. I'm wondering if the transformer might be loading the level down. Sounds like you may just need to boost the audio to the radio.
 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
Check the audio level out from the PC at max volume without connecting to the relay circuit. I'm wondering if the transformer might be loading the level down. Sounds like you may just need to boost the audio to the radio.
That is exactly what I was going to do next. What is strange is that it was working and I made a couple of contacts and then it just stopped delivering the necessary level. I’m thinking the input to the transformer was just at the hairy edge. So it might need some amplification. Would that go before or after the xfmr?
 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
After the xformer. I'm working on a new circuit. Do you have any op amps like a LM358?
I do not but I can always order one. Just as an FYI I bypassed the audio isolation transformer and the radio still does not xmit audio.The relay latches but I’m not getting enough audio from the pc to the rig now. I was this afternoon. Bugger.
 

MisterBill2

Joined Jan 23, 2018
11,590
Do you have a link to this circuit? I like the 555 it’s an old friend
The circuit and the article are printed in many versions of "The Radio Amateur's Handbook", published by the ARRL. I do not have a link, any web search should turn up some access information. I would avoid the much newer editions because they seem to be far less hardware oriented.

And if a circuit that had been working satisfactorily suddenly stops working, the first suspect would be a failed connection some place. So I suggest verifying that the signal is still getting to where it needs to be at an adequate level. And a good VOX circuit can work with a microphone output level, as low as 50 millivolts. (0.050 volts.)
 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
After the xformer. I'm working on a new circuit. Do you have any op amps like a LM358?
OK, hold the phone again. It logically didn’t make any sense that the radio is getting audio and not transmitting so I unplugged our circuit and plugged in the microphone. The issue was in the radio. I need to open it up and do some troubleshooting there. So hold off on that amplifier. Thank you again for your assistance
 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
The circuit and the article are printed in many versions of "The Radio Amateur's Handbook", published by the ARRL. I do not have a link, any web search should turn up some access information. I would avoid the much newer editions because they seem to be far less hardware oriented.

And if a circuit that had been working satisfactorily suddenly stops working, the first suspect would be a failed connection some place. So I suggest verifying that the signal is still getting to where it needs to be at an adequate level. And a good VOX circuit can work with a microphone output level, as low as 50 millivolts. (0.050 volts.)
Yes thank you I came to the same conclusion and then I just had to look at the transmitter and discovered that it keys up but is not transmitting any audio even with the microphone. So I got a problem in the radio. The circuit that our other friend provided was working brilliantly until the radio crapped out. Just something else for me to do ;)

Thank you for your suggestions and for joining the conversation
 

MisterBill2

Joined Jan 23, 2018
11,590
Finding the problem in a radio is like most other diagnostic task. First, know how it works and what each section does, and then examine and see which section is not doing as it should. That will point very closely to the failed part or failed connection.
Is the radio still receiving, and does it deliver a carrier when commanded to transmit? two fairly simple things to verify. Then, is the audio even reaching the radio? And is the radio really getting the transmit command? Not even with the microphone? Then check the selector between microphone and external audio input. ( all of this is just verifying blocks in the block diagramthat I have not even seen.
 
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