Audio Interference with SDR on Broadcastify Calls?

[Kingscup]

I am providing a feed to the Calls platform and I seem to have some sort of audio interference being uploaded to the feed. Most times, it only happens on 1 or a couple of frequencies. Other times, it is on all frequencies. It generally lasts 3-5 seconds. I am able to filter out much more by not having it upload anything less than 2 seconds. I woke up this morning and it was going crazy. I have attempted to Google RF interference audio but I could not find any sounds that sound like this. Here is a copy of the audio. Audio Interference

I am using Trunk Recorder with conventional analog frequencies on 2 RTL-SDRs and a Raspberry Pi 4. 151 MHz and 153-154 MHz. I have turned off everything in the house with the exception of the RPi and USB hub and it still happens. I have many theories but nothing concrete. Any ideas?

 

[krokus]

Is that all the time, or just when scanning? Just one SDR, any of them? Have you tried other freqs, such as NOAA weather?

 

[Kingscup]

I am monitoring 11 frequencies off of 2 SDRs. Sometimes it only happens on one frequency or a few. Other times it is on all frequencies on both SDRs. It seems to be random times. It only happens when there is no radio traffic as I believe the signal is stronger than the interference. The Calls platform doesn’t scan frequencies. The SDR monitors each frequency at the same time 24/7 and then uploads the audio to Broadcastify.

 

[ScanYak]

I experienced something similar to this, using the same setup, Pi 4 conventional analog. I noticed it occurred while 2 recorders were recording different frequencies at the same time on the same SDR. I found some success by adjusting squelch and gain settings. It may or may not be the same problem.

 

[Kingscup]

I experienced something similar to this, using the same setup, Pi 4 conventional analog. I noticed it occurred while 2 recorders were recording different frequencies at the same time on the same SDR. I found some success by adjusting squelch and gain settings. It may or may not be the same problem.

I can't tell for sure but I don't think that is the problem. I can see that maybe the gain/squelch settings might be a problem. I have them set fairly high as I am trying to reach as much of the county as I can. The county is not on simulcast. They use repeaters as more of a regional repeater vs a countywide simulcast system. Thanks for the suggestion.

 

[Kingscup]

I started this thread after moving my Calls setup further away from the other electronics (computer, scanner etc) but this caused constant interference. After tweaking things and rebooting the RPi 4, things settled down. I tweaked the squelch and gain settings some more as ScanYak suggested. I do notice more interference on the command prompt screen but I have filtered out anything less than 2 seconds to not upload to the Calls system. So far, interference uploads seem to only occur once or twice a day from what I can tell. I am happy with that if it stays that way.

A couple of other things I have noticed since the move. It may be similar to ScanYak's problem earlier. When 2 SDRs are recording at the same time, I can hear the other SDR transmission in the background of the first SDR transmission once it is uploaded. This didn't happen in the past. Because of the new location of the RPi, I had to daisy chain a second multicoupler for the antenna wires to reach the RPi. That is the only thing different with the setup. I am also using a USB hub since the beginning. I am wondering if I need a better quality one. It is not a cheap one but maybe not the best either.