[arm-allstar] hum on my allstar nodes

[Michael Fleetwood]

I am having a problem with a background hash others hear when I 
transmit using a radioless node with a Pi3A+ an Alinco EMS57 mic, 
modified sound fob and audio amp. Received audio is perfect, but when 
I listen to myself on the parrot the noise sounds a bit like an FM 
signal that is not fully quieting. I have tried optimising grounding 
and using different power supplies including a 12v battery and 7805 
regulator, but the problem persists.

Mike
VK2AMF


At 05:23 AM 27/04/2020, you wrote:
>The "RF" hum is caused by some odd phasing relationship and/or RF overload
>at the site. When you think of it you rarely transmit RF that close to the
>destination most of the time. We have found that distance and selecting
>locations that are best are about the only thing you can do in this case.
>It usually only happens when you are very close to the node. If this is
>your problem the only thing you can do is change locations of equipment or
>antennas and distance from your node.
>
>*73 Doug, WA3DSP*
>*http://wa3dsp.org <http://wa3dsp.org>*
>
>On Sun, Apr 26, 2020 at 11:57 AM "Chris Smart via ARM-allstar" <
>arm-allstar at hamvoip.org> wrote:
>
> > Thanks Doug.
> >
> >
> > What is typically the source of this hum? Wall-wart type power supplies?
> >
> > 73
> >
> >
> > Chris
> >
> >
> >
> > On 4/26/2020 10:46 AM, "Doug Crompton via ARM-allstar" wrote:
> > > Hum on local RF nodes is a common problem when transmitting TO your node.
> > > It is usually because you are too close to your node. If the hum stops
> > when
> > > you move to another location, sometimes just a foot or two one way or the
> > > other then that is probably the problem. It happens more often when using
> > > antennas that are mounted on the node itself. One way to get rid of it is
> > > to use those small mag mount antennas that have 10-15 feet of coax and
> > get
> > > it away from your operating position or use an outdoor antenna. Other
> > than
> > > that there is no filtering or other way to eliminate it. If the hum is
> > > constant at any location even walking hundreds of feet away then it is
> > not
> > > this phenomenon.
> > >
> > > *73 Doug, WA3DSP*
> > > *http://wa3dsp.org <http://wa3dsp.org>*
> > >
> > >
> > >
> > > On Sun, Apr 26, 2020 at 4:08 AM "Jed Barton via ARM-allstar" <
> > > arm-allstar at hamvoip.org> wrote:
> > >
> > >> Hey guys,
> > >>
> > >> So i'm sure i'm not the only 1 with this problem. I've got all my
> > >> allstar pies plugged in.  They each have their own power supply. It's
> > >> the typical wall wart.  They all produce a nice little hum that's just
> > >> annoying.
> > >> I'm sure a lot of you guys have delt with this.  You hear it on the
> > >> node transmitter such as the Shari.  Any ideas for getting rid of it,
> > >> or reducing it?
> > >>
> > >> Cheers,
> > >>
> > >> Jed
> > >> _______________________________________________
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> > >>
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> > >>
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> > >
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> > >
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> >
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> >
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> >
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>
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Mike Fleetwood
Canberra Australia and Sidcup UK.

Worldwide email address is:     mfleetwood at gmail.com