I am working on setting up a new simplex node and I thought I’d try out the CM119B board from technobygeorge.com. I have the “ARA-1+” board.
Out of the box, the green heartbeat LED blinks as usual, PTT works, COS probably works (haven’t really got that far yet), and audio output from the CM119B works.
However, I am unable to get any audio input to show in the simpleusb-tune-menu, nor with the USBradio module and radio-tune-module. No audio is shown in the menu “bar” meter for either. I tried several gain values from 0 to 999. My audio source is a 1 KHz tone at 1Vpp. I should see a little bar drawn across the screen showing the audio level, correct?
Connecting the CM119B module to my desktop Linux box (Mint 20) works fine, audio flows as expected, gain controls work, etc. This tells me the hardware is, in principle, working with my audio generator and connection.
Can anyone advise on how to get this working, or if it’s a known problem? I’m fully comfortable with asterisk configuration files and linux commands, I’ve had nodes running for nearly a decade now using CM118 hardware.
You’re probably right, I could get along ok without COS. But I have a nice GE Phoenix here all tuned up with Channel Guard, so I’d like to use it :). Call me old-school but I do really like these radios and a proper COS/CG signal.
I read some posts on the archives here that came up searching for “CM119B” and from what I can tell, it isn’t the preferred chipset at all. I’m kind of surprised that an audio device needs a dedicated crystal for stability (you’d think the USB clock, once divided down enough, would be pretty stable!). At any rate, if anyone knows how to squeeze audio in that would be great. The device definitely works fine in linux for other purposes.
That’s what I was getting at but I wasn’t clear… I’m not at all sure the VU (receive level display) meter on simple-tune-menu works if there is no COS of CG as appropriate.
I’m with you there. I always use the repeater’s P/L, both encode and decode. And there’s nothing better that the 'ol reliable Micor squelch chip. However, I’ve found the RTCM units squelch circuit does a darn good job.
I also like to use the repeater’s pre/deemphasis filters. You were probably reading @kuggie posts on the CM119. I know he disagrees with me on that and is a big fan of USBradio which I am not. But that’s ok. We’re still good friends
I’ll take another stab at it, forcing the COS to ON.
Which do you think sounds better – discriminator audio into asterisk with the software filters, or “speaker” audio into asterisk without software filters? I can go either way here with the GE. Same goes for transmit actually.
I can tell you, from looking at the analog audio output on the CM119B and the CM108, the anti-aliasing is awful. There’s not been much effort within the chip to smooth out the waveforms, and you can clearly see the sample rate staircase in the output. Presumably once you’re working with an 8 KHz sample system this would disappear, but it sure is ugly! The connection to pre-emphasis is that if one injects audio into the radio’s transmitter, there needs to be adequate filtering to remove the spurs caused by these converters. (If you want to see for yourself, run a CM108 or 119B at 44.1 KHz and play back a 3 KHz sine wave. It’s frightening.) Maybe this is why the more expensive URI box has so much filtering…
Some people would say that you should use the AllStar filters if you have different repeater hardware in your network. That way all repeaters sound the same.
You bring up a good point about anti-aliasing. Perhaps the choice of sound dongles is more critical than people realize.
With the official ASL Pi image, should the CM119B show up in alsamixer? Mine does, I wonder if there’s a conflict preventing it from working as an audio input?
That’s an interesting point about the uniformity of the (filtered) audio between nodes. With software, we can get them all on the same slope. Personally, I may be changing my repeater soon to not use asterisk as the “through” audio processor. I think it sounds a bit more “squeezed” than it could.
You know what? It was COS the entire time. Once I correctly activated COS, the VU meter responded as expected. Both RX and TX audio seem correct, with functioning level controls.
That VU meter really should have a message when COS is off, “Waiting for COS”. Or maybe it could show level either way – that would be useful for me with my GE repeater where the audio is always available.
Y’all accepting pull requests for this kind of stuff?
Take care, and thank you for the work you are doing,
