[arm-allstar] Asterisk - Hum

[Chris Souleles]

I know you have received a number of replies but I thought I would give you my experience.  
I built a couple nodes with BF888, RPI3 and DMK URi.  I run them off 12 VDC because I use them mobile as well as at my home.  I used two DC/DC converter adjustable regulators, one set at 5.1V for the RPI3, the other at 4.0V for the BF888.  I twisted all DC power wires and they are no longer than 5 or 6 inches except for the main 12 volt from the DC source to the node power input which is about 8 feet,  I soldered the 5.1 V directly to the RPI3 board to avoid using the micro usb connector for power. I soldered the 4.0 V directly to the BF888 circuit board.  The cable from the BF888 to the DMK USB/Radio interface is about 6 inches long.  I use a 12 inch whip installed directly on the radio.  The radio is out of it's case to facilitate my particular installation.  It is all installed in a plastic tupperware case.    
No hum and I get good signal reports from my house and mobile through my iPhone hotspot.  I have also run the node from a switching power supply set to 12 volts and it also works fine with no hum.
I am not sure of your exact set up, but hum in the audio often comes from the power supply, power supply wiring or ground loops. 
Chris - W6CS - 73



      From: Eric Smyder via arm-allstar <arm-allstar at hamvoip.org>
 To: arm-allstar at hamvoip.org 
Cc: Eric Smyder <N3FIX at qsl.net>
 Sent: Wednesday, December 13, 2017 2:15 PM
 Subject: [arm-allstar] Asterisk - Hum
   
Hello all:

I've been experimenting with HAMVOIP, on a Pi3 at the home QTH with a
BF-888s as my radio.  It is a remarkably good system and easy to
configure.  However, I'm having an issue.  It is actually the same issue I
noticed on the W3HZU 6 meter repeater.

The video links below exemplifies the issue.  When transmitting directly
from the repeater with the hand-mic the repeater sounds great.  When I
trigger the AllStarLink from Asterisk, or when the node makes an
announcement or identifies, there is a distinct tone or hum.  I get the
same thing on my Pi 3 at the house if I key the transmitter and speak into
the BF-888s.  It seems to be coming through the computer or being picked up
somewhere in the connections to the URI.  I have taken measures to shield
the wiring between the radio and the URI, but the hum is still there.

At W3HZU 6m AllStarLink
https://photos.app.goo.gl/OtJn3aK2ZRCd6cPs2

At the home QTH using the Pi3, where the hum is more noticeable.
https://photos.app.goo.gl/XsUC4on5t04LH6CS2

Has anyone else noticed this and is there something I can do about it?

Thanks,

Eric
N3FIX
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