[arm-allstar] USB Cables With the Most Shielding?

[David McGough]

Hi Chris,

If you're hearing the whine on both RX and TX, the noise is probably audio
path related; likely a ground loop or other ground noise.

What type of power supply are you using on the RPi board?  I have seen
situations where very noisy AC switching power supplies (mostly "wall
warts") would produce a whine that got in the audio. Frequently these have 
significant and detectable AC leakage showing up as common-mode noise on 
the DC power output.  This can rip the USB audio to shreds!

I know numerous different power supply and wiring protocols have been
developed and adopted by various AllStar users.  I prefer powering the RPi
board via a DC-DC converter, directly from the radio/repeater power
source.  I keep all my grounding points a the same physical spot,
minimizing the potential for ground loops / noise.  Since I went to this 
strategy, my audio noise issues have reliably disappeared.


73, David KB4FXC


On Tue, 15 Jun 2021, "Chris Smart via ARM-allstar" wrote:

> Hmm, good question.
> 
> Right now it's completely gone, but if I move that USB cable a little, I 
> can bring it back easily enough. Sometimes I hear it on TX, sometimes on 
> RX. sometimes both.
> 
> 
> 
> On 2021-06-14 10:38 p.m., "David McGough via ARM-allstar" wrote:
> > Hi Chris,
> >
> > How is the whine getting into your node---via an audio or RF path??
> >
> >
> > 73, David KB4FXC
> >
> >
> > On Mon, 14 Jun 2021, "Chris Smart via ARM-allstar" wrote:
> >
> >> Hi.
> >>
> >>
> >> I'm running an Alinco node radio and the RIM-Alinco device, along with
> >> the supplied short, very thin USB cable. I'm tired of gently moving the
> >> bulk of that USB cable around, an inch this way or that, and it going
> >> from major USB wine (1,046 Hz) to nothing.
> >>
> >>
> >> Do people here have a prefered brand of USB cable with lots more
> >> shielding, including ferrite? I believe I need USB-A to MINI-B, right? I
> >> always get mini and micro B confused.
> >>
> >>
> >> I'm also going to put a serial cable on the back of that port so I can
> >> get the RIM-Alinco much farther away from the transmitter, since it's
> >> running 5 watts.
> >>
> >> I want the best-sounding, quietest node in town, and I"m almost there. :)
> >>
> >>
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> >>
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> >>
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