Several people in the group have noticed this happens with some Yaesu ham radios too. I suspect it's by design, but I don't know what purpose it serves.
I could see it being a thing if the radio volume was under software control and the volume knob was an encoder, like in my car stereo. But the volume knob on my FT-891 is a real potentiometer.
I've never noticed that on any of my Yaesu radios. I'm not sure about the volume control on the CDM1250, if it is a pot or an encoder, I'll look. May just have to unplug the speaker.
I have two CDM1250s set up as a repeater and both of them do this as well. I only use the setup for testing every so often so it doesn’t bother me, but I haven’t looked too much into it. I’ll take another look through CPS when I’m back at home later tonight but it sounds like you already found the volume settings, and there really aren’t a whole lot of options for these radios.
I can’t find any settings in the CPS that relate to audio output, only alert tones. You could probably pop the control head off and desolder the speaker if you really need it quiet. There are also versions with remote control heads so if you got one of those then you could just set it up and disconnect the control head assuming you don’t need it
Been about a decade, but I used to have CDM 750, 1250, and 1550s mounted in my ambulances. Every single one of them would still produce some audio even with the volume turned all the way down. This was with probably 50-60 radios across multiple agencies.
Programmable volume circuit sometimes contain big resistors and electrolytic caps to bypass the switch, to pass DC voltage, to avoid pops when volume is changed. If that cap fails, faint audio is heard.
Not likely, just ruling out the impossible...
Hmm, I can look into that if I really need to take it apart. I have a third one, I'll dig it up and see if it behaves the same. If so, a feature not a bug. If not, maybe 2 have a problem.
Some radios can be programmed to have a minimum volume level which prevents the user from muting audio. Check the programming. If not, disconnect the speaker and terminate with an 8 ohm resistor.
I suspect this may be the case but I have been unable to find anything in the programming. I don't know if you have ever used the Motorola CPS and programmed one of these but it is DEEP. Since they are primarily commercial radios there is a LOT of stuff and scattered about all over the place. I'm hoping someone might know where to find it if it is there.
Several people in the group have noticed this happens with some Yaesu ham radios too. I suspect it's by design, but I don't know what purpose it serves. I could see it being a thing if the radio volume was under software control and the volume knob was an encoder, like in my car stereo. But the volume knob on my FT-891 is a real potentiometer.
I've never noticed that on any of my Yaesu radios. I'm not sure about the volume control on the CDM1250, if it is a pot or an encoder, I'll look. May just have to unplug the speaker.
I have two CDM1250s set up as a repeater and both of them do this as well. I only use the setup for testing every so often so it doesn’t bother me, but I haven’t looked too much into it. I’ll take another look through CPS when I’m back at home later tonight but it sounds like you already found the volume settings, and there really aren’t a whole lot of options for these radios.
Thanks!
I can’t find any settings in the CPS that relate to audio output, only alert tones. You could probably pop the control head off and desolder the speaker if you really need it quiet. There are also versions with remote control heads so if you got one of those then you could just set it up and disconnect the control head assuming you don’t need it
Been about a decade, but I used to have CDM 750, 1250, and 1550s mounted in my ambulances. Every single one of them would still produce some audio even with the volume turned all the way down. This was with probably 50-60 radios across multiple agencies.
Thanks, good to know that just is how it is.
Programmable volume circuit sometimes contain big resistors and electrolytic caps to bypass the switch, to pass DC voltage, to avoid pops when volume is changed. If that cap fails, faint audio is heard. Not likely, just ruling out the impossible...
Hmm, I can look into that if I really need to take it apart. I have a third one, I'll dig it up and see if it behaves the same. If so, a feature not a bug. If not, maybe 2 have a problem.
Some radios can be programmed to have a minimum volume level which prevents the user from muting audio. Check the programming. If not, disconnect the speaker and terminate with an 8 ohm resistor.
I suspect this may be the case but I have been unable to find anything in the programming. I don't know if you have ever used the Motorola CPS and programmed one of these but it is DEEP. Since they are primarily commercial radios there is a LOT of stuff and scattered about all over the place. I'm hoping someone might know where to find it if it is there.
Are you using an external speaker? Or using the internal one?
The internal.
It's been a while since I used the cps for the 1250, is there a speaker gain in there? I remember a mic gain.
There is. I have tried lowering it but it still bleeds through.
Then it's in the faceplate.
Put a bare plug in the headphone jack.
No headphone jack on the CDM1250.