MCC7500 clipping audio
Posted: Mon Mar 21, 2022 11:37 am
Trying to troubleshoot an issue that has been occurring for over a year in our environment with not much progress from the service provider. On our analog VHF channels, we've been having an issue where sometimes dispatch misses an entire transmission, or more frequently misses pieces of a transmission. Field units listening via RF have no problem hearing these transmissions.
The missing audio is absent from the recorder and all the consoles (10 positions). To me it seems like the audio is being gated or not meeting some audio squelch level. On the field side, I can always hear the carrier when someone is keyed up, even if they are not speaking. On the logger and console side, it will go completely silent. I would expect, at the logger/console side, to never drop or gate the audio if it doesn't meet a certain threshold.
Here is some example audio of the issue:
https://sndup.net/b8f3/ - lots of clipping here.
Here is the same transmission recorded from a scanner: https://sndup.net/x2y8/
Other examples of clipping:
https://sndup.net/bvx6/ - clipped after "engine 73", transmission resumes - on the field side, the audio was never clipped
https://sndup.net/g2bs/ - clipped after "county road 24", transmission resumes - on the field side, the audio was never clipped
https://sndup.net/gg4w/ - audio seems to be clipped as there is no trailing "splash"
The missing audio is absent from the recorder and all the consoles (10 positions). To me it seems like the audio is being gated or not meeting some audio squelch level. On the field side, I can always hear the carrier when someone is keyed up, even if they are not speaking. On the logger and console side, it will go completely silent. I would expect, at the logger/console side, to never drop or gate the audio if it doesn't meet a certain threshold.
Here is some example audio of the issue:
https://sndup.net/b8f3/ - lots of clipping here.
Here is the same transmission recorded from a scanner: https://sndup.net/x2y8/
Other examples of clipping:
https://sndup.net/bvx6/ - clipped after "engine 73", transmission resumes - on the field side, the audio was never clipped
https://sndup.net/g2bs/ - clipped after "county road 24", transmission resumes - on the field side, the audio was never clipped
https://sndup.net/gg4w/ - audio seems to be clipped as there is no trailing "splash"