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396XT Speaker Noise
Posted: Fri Jan 20, 2012 12:17 pm
by pks
Has anyone noticed a short burst of noise from the speaker right after a keytone while listening to P25 transmissions? For eg, during a P25 transmission, if I press any key to cause a beep from the speaker, I would hear a short burst of noise right after the beep. This also happens after the beep of low battery. Anyone else experienced this?
Re: 396XT Speaker Noise
Posted: Tue Feb 14, 2012 12:03 pm
by commsmc
I have noticed this recently, it's quite annoying. Sounds something like 'psssst'. I think it only occurs when there is P25 audio being decoded and a 'beep' comes through...
Mike
Re: 396XT Speaker Noise
Posted: Tue Feb 14, 2012 12:36 pm
by Bigfella237
Sounds to me like DSP is being stopped to allow the beep to have full use of the speaker, then takes a fraction of a second for processing to restart?
Andrew
Re: 396XT Speaker Noise
Posted: Tue Feb 14, 2012 3:45 pm
by citabria
P25 only sends its frame sync every 180ms during a voice transmission, so if the scanner stops and loses sync (ie, its busy playing a beep or whatever) then it can take up to 180ms before a frame sync is sent again. The frams sync is what the radio uses to identify a P25 transmission, so until this is sent, the radio treats the transmission as FM.