<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>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. </div><div>Thanks Doug, and everyone else, for bearing with all the questions, hopefully some other newbie will find them helpful one day in a search. </div><div>73</div><div>KJ6QFS</div><div><br>Sent from my iPhone</div><div><br>On Oct 31, 2014, at 6:15 PM, Doug Crompton <<a href="mailto:doug@crompton.com">doug@crompton.com</a>> wrote:<br><br></div><blockquote type="cite"><div>
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<div dir="ltr"><font style="" color="#000000" face="Tahoma,sans-serif">Sam,<br><br> 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.<br><br>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.<br id="FontBreak"></font><br><b><font style="font-size:16pt;" size="4">73 Doug</font><font style="font-size:16pt;" size="4"><br></font><font style="font-size:16pt;" size="4">WA3DSP</font><font style="font-size:16pt;" size="4"><br></font><font style="font-size:16pt;" size="4"><a href="http://www.crompton.com/hamradio">http://www.crompton.com/hamradio</a></font></b><font style="font-size:16pt;" size="4"><br></font><br><br><div><hr id="stopSpelling">Date: Fri, 31 Oct 2014 14:06:54 -0700<br>From: <a href="mailto:kj6qfs@gmail.com">kj6qfs@gmail.com</a><br>To: <a href="mailto:arm-allstar@hamvoip.org">arm-allstar@hamvoip.org</a><br>Subject: [arm-allstar] URI audio noise<br><br><div dir="ltr">Hello again to all, <div>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. </div><div>Here's the troubleshooting I did so far, to no avail.</div><div><br></div><div>*double-checked my grounding between the URI and controller. ( RLC-4 radio port pin 1 -> URI pin 13) </div><div>*tried different USB cables between URI and BBB</div><div>*tried powering BBB with mini-USB cable attached to charger-less laptop instead of my +5V wallwart</div><div>*tried powering BBB with USB cigarette adapter plugged into controller's +12VDC supply</div><div>*tried removing ethernet cable </div><div><div><br> Any tips/ideas would be greatly appreciated. </div><div>Thanks!<br><br></div><div class="ecxgmail_signature">KJ6QFS<br>Sam Skolfield</div>
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