I’m trying compare different audio settings. This includes two different URIs. Also different settings on a Motorola CDM1550 LS need to be compared. There’s too much time between simple A/B comparisons because changing settings is time consuming.
One idea is to use an audio recorder on a smartphone to record audio when played back from a parrot node. This is perhaps the most easiest way for a quick A/B comparison between two settings.
Another idea is to somehow tap into the parrot playback with an audio spectrum analyzer. That removes the subjectivity my hearing.
This is all based on the difficulty I’m having getting my CDM radio dialed in from an audio perspective. I’m having issues getting the deeper audio response present in the Allison telemetry. My parrot audio playback sounds tinny by comparison missing lower frequencies.
If you’re hearing tinny audio, Check your emphasis settings. The 1550 itself should be programmed for flat audio, and both de-emphasis/pre-emphasis should be enabled in simpleusb, or the option set to flat in usbradio, depending on what you’re using.
Also make sure you have plfilter enabled in simpleusb. usbradio defaults to a 300hz high pass filter (rxhpf = 0), but I prefer using option 1, which is less steep at 250 Hz.
@N2DYI
I have an idea. I recognize your callsign and looked at your qrz bio. Perhaps we could meet on the air if that’s okay. There’s a few things that make me think my 1550 is off. Such as ridiculously low audio requiring max mic gain. Basically I need a Motorola guru!
Let know if you’re okay with meeting on the air and how to connect.
In case on the air help isn’t an option, I’m concerned my 1550 might be a dud. I bought it nearly 4 years ago and used it briefly in DMR mode with a Zumspot modem board. So it wasn’t ever used with regular analog FM until recently. If I use flat rx audio, the audio level is so low I have to compensate with max mic gain. So something doesn’t seem quite right. Also I have to max out the rx level in SimpleUSB.
I’d like to try USBRadio but feel more than a little lost. The PTT acts very different from Simple USB. But I’m willing to try USBRadio if it solves my problem.
Well, I’m not a Motorola guru as such. I built my first ASL node using an old Radius SM50, which was programmed with dosbox. With that radio, I could get away with the RX gain about half way (500) and RXBoost enabled.
If that radio was set up for mototrbo, then you likely would need about 20Db more gain from ASL than you would otherwise. That could just be a programming thing, but I can’t really help much with that radio, or even that series of radios in particular.
I’m coming at this from having tried to use a Kenwood TM-V71A mobile radio set up for 9600 input, which would have required a preamp. Maxing everything out was still too quiet, and it distorted… very quietly. So, I compromised, and wired a cable such that it received from 1200 and transmitted on the 9600 pin-out to get the best audio I could out of that radio.
I am currently monitoring node 508429 if you’d like to chat.
I’ve made a major discovery. There’s an intermittent in the receive section of my 1550. This is something I’ve encountered before. That is the receive input will get way overloaded. And I have to crank the RX Voice Level way down. And then once that’s done usually it will get weak again and I’ll have to max the RX Voice Level way back up. This is a recurring issues I’ve had with each URI and on two different RPi hosts. So it looks like the issue is in the 1550 itself.
The difference today with that the lower RX Voice Level value, about 300, worked for a few hours. Then suddenly I was unable to get the DTMF tones to work. That’s when I set the RX Voice Level to almost max and suddenly it was overloading. I’ve been able to run this max value indefinitely in the past. But today a short burst of my voice seems to have unstuck something and I’m now able to use a value of 300 again.
This makes me think there’s an intermittent in the 1550 radio hardware where the receive audio on the rear connector is flaky. I’m tempted to buy a replacement radio to see if it gets stable again. The rear connector is very solid feeling. Just wish I knew how to fix it. The fact the issue is present with two different URIs points to the radio as the culprit. I believe the rear connector pin is #11?
I’m hoping posting this might remind someone of a similar problem with a fix. Perhaps contact cleaner?
Some random notes… the USBRadio tune menu needs a lot of work. Setting rxmix level there rarely if ever actually changes the mixer setting in the CM1xx IC. If you run the various menu options enough times it eventually calibrates itself appropriately but it’s unintuitive, misleading and unreliable. I often see it working fine for days or weeks and then suddenly one day won’t detect carrier or CTCSS and I have to rerun the calibration steps. And there seems to be almost no documentation on the process other than how to calibrate things with a service monitor which most people who don’t own repeaters will not have. I have a customer who had a similar issue as described above, very low audio out of a TM-V71, spent hours in the tune menu and no matter what he did USBRadio would not increase the rxmix gain. Finally I sent him my .conf file from my setup with the same radio and URI and then everything worked fine. Someday when I have time I plan to go through chan_usbradio.c and clean all this up and document exactly what the menu options are doing, what the settings (eg. rx…adj) are, how they are calculated and how they translate into the CM1xx mixer settings. I suspect there will a number of issues uncovered during this process and some ways to make this much clearer and more robust. The ‘R’ Show Rx Audio Stats function I added a couple months ago is often the only way to see the actual audio levels coming in from the ADC. It would be easy to also add a function to show an FFT or wavelet transform spectrum, will see if I can add that soon.
@N2DYI
I’m fairly certain my problem is solved. However I haven’t been able to contact you on 508429 since that one QSO. I’d like to follow up you on 508429 and do a post mortem.