[App_rpt-users] Random Keyup & Hum

[Sam Nabkey]

Sounds like 120hz from a bad power supply or an HT in a charger.  Changing
the pl away from 123.0 would eliminate the repeater keying but it still
would be present on the input.

Over my 30 plus years of repeater building  for commercial, public service
and amateur service I've seen lots of things causing this.  TV preamps long
forgotten in attics killing VHF repeater inputs and old unstable garage
door opener receivers wiping out a large segment of 455-458mhz miles from
the repeater.

Listen on the input from various parts of the coverage area and see if you
can hear it.  Start at the site and move away.

Good luck!

Sam - K8SN


On Jan 29, 2015 1:04 PM, "Mark Johnston" <markjohnston73 at gmail.com> wrote:

> Does anyone know what might cause this, (attached audio file)
>
> I was having this on my node, using a GE Mastr II with URI and DSP to
> decode the PL tone
> 123.0 - my first thought was feedback loop from the TX but it just happens
> without anyone keying up or an ID occurring.
>
> However also considered someone jamming / txing a near dead carrier with a
> hum on their signal.
>
> Tried reboot, and this would happen whether I was connected or not, it
> also has the courtesy tone, which is the local tone, as if it was a station
> here (local).
>
> Changed the PL lower in freq and it all cleared up. Not sure what could
> have caused it though?
> As far as I know nothing has changed at the repeater site, haven't been up
> there in ~ 2 months since the last change where I raised the antenna, from
> 10 to 30' and brought it about 15' closer to the repeater.
>
> If anyone has a thought other then some station keying up to cause this,
> jamming etc... what else could happen to do that?
>
>
> 73's
>
> Mark KC7DMF
>
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