[arm-allstar] hum on my allstar nodes

[David McGough]

Mike,

With radio-less nodes, the biggest issue I've had is noise of the power 
for the mic element. This gives just like you're describing: everything 
from hissing sounds to various hash/hum noises.

How are you powering your mic circuit? 


73, David KB4FXC

On Mon, 27 Apr 2020, "Michael Fleetwood via ARM-allstar" wrote:

> 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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> > >
> >_______________________________________________
> >
> >ARM-allstar mailing list
> >ARM-allstar at hamvoip.org
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> >
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> 
> Mike Fleetwood
> Canberra Australia and Sidcup UK.
> 
> Worldwide email address is:     mfleetwood at gmail.com 
> 
> _______________________________________________
> 
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>