[arm-allstar] URI audio noise

[Samuel Skolfield]

You wouldn't believe it! I completely eliminated the noise by moving my ground from URI pin 13 to pin 20. The Schematic that DMK offers for the URI shows all Ground pins tied to a common ground point, so maybe this is specific to mine. 
Thanks Doug, and everyone else, for bearing with all the questions, hopefully some other newbie will find them helpful one day in a search. 
73
KJ6QFS

Sent from my iPhone

On Oct 31, 2014, at 6:15 PM, Doug Crompton <doug at crompton.com> wrote:

> Sam,
> 
>  A scope would be real helpful in tracing this. It sounds like switching power supply noise. This could also come from a fan as many small fans used for rig cooling are actually AC fans with internal switchers. I have often seen this type of EMI and a RC filter works well in that case. About a 30-50 Ohm resistor in series and a 500-1000uf cap to ground on the 12V lead to the fan.
> 
> I don't think this is a normal thing with the URI or a large number of us would be seeing it on our systems. Something specific to your setup is causing it. With all of your tests I think I would rule out a ground loop or power supply to the BBB.
> 
> 73 Doug
> WA3DSP
> http://www.crompton.com/hamradio
> 
> 
> Date: Fri, 31 Oct 2014 14:06:54 -0700
> From: kj6qfs at gmail.com
> To: arm-allstar at hamvoip.org
> Subject: [arm-allstar] URI audio noise
> 
> Hello again to all, 
> I've interfaced a DMK URI to an RLC-4 Repeater controller. Everything works great, with the exception of the common "USB noise" (high-pitched whine, sounds like square wave) on both TX and RX audio from the URI. 
> Here's the troubleshooting I did so far, to no avail.
> 
> *double-checked my grounding between the URI and controller. ( RLC-4 radio port pin 1 -> URI pin 13) 
> *tried different USB cables between URI and BBB
> *tried powering BBB with mini-USB cable attached to charger-less laptop instead of my +5V wallwart
> *tried powering BBB with USB cigarette adapter plugged into controller's +12VDC supply
> *tried removing ethernet cable 
> 
>  Any tips/ideas would be greatly appreciated. 
> Thanks!
> 
> KJ6QFS
> Sam Skolfield
> 
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