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

[David McGough]

Chris,

Switching wall-warts don't typically have 60Hz or 120Hz audio noise. It's 
almost always much higher frequency buzz---like in the 1KHz to 3KHz range.

Since the noise is intermittent, some type of poor connection (somewhere) 
might also be the cause.


73, David KB4FXC


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

> I'm using the wall-wart I bought with a Pi 4.
> 
> I have a ferrite choak on its cable right at the Wall-wart end, and I am 
> not hearing 120 Hz on my audio.
> 
> 
> Now it's just the 1,046 Hz I'm sortig out. right now it's absent, as 
> long as I don't move anything on the desk. :)
> 
> 
> 
> On 2021-06-15 8:55 a.m., "David McGough via ARM-allstar" wrote:
> > 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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