[arm-allstar] Noise on the output rpi2 and uri.

[Doug Crompton]

Andrew,

   You didn't describe what the noise sounds like but most noise comes from some switching source. It could be a cooling fan, a switching power supply, etc.  Also have you eliminated RF problems? Since this is on TX only maybe put the transmitter on a dummy load just to check. Are you using shielded cable for the radio connection? Are the grounds all good?

You need to probe at different points along the path to see where the noise is being introduced. Asterisk Allstar itself would not introduce any noise, at least not objectional noise as you describe.  

What are you using for a power supply for the 5 volts? 
73 Doug
WA3DSP
http://www.crompton.com/hamradio


Date: Sun, 24 May 2015 23:41:41 +1000
From: andrew.gilbett at gmail.com
To: arm-allstar at hamvoip.org
Subject: [arm-allstar] Noise on the output rpi2 and uri.

Hi All,
I have just setup a RPi2 & URI combo and it work quite well. Except it has quite a high noise level on the tx.
I noticed that this was also the case on the beagleboard xm and lox board combo as well. I was hoping it was peculiar to that hardware but it is not unfortunatly.
Basically it sounds like it is being encoded with gsm  and being compressed with noise added to it.
If I connect via IAXRPT the signal is quite clear but not perfect so there is a little bit of noise on the input but it is the output where it is degraded again.
I am using Simoco SRM9005 radios using the rear io on the db15.
Could someone shed a little light on the audio path through asterisk and where noise could be coming from there?
This is for an ultra portable repeater that is carried up hills for events and I have found that apt_rpt and asterisk is awesome because it is a complete voip switch. Keep up the good work.
Andrew

VK2XAG

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