[Moon-Net] QRM on 1296.000

Mary Brown maryalanab at gmail.com
Thu Nov 10 05:01:56 CET 2016


Wifi oscillator maybe... 

-----Original Message-----
From: moon-net-bounces at mailman.pe1itr.com [mailto:moon-net-bounces at mailman.pe1itr.com] On Behalf Of Courtney Duncan
Sent: Wednesday, November 09, 2016 9:50 PM
To: moon-net at mailman.pe1itr.com
Subject: [Moon-Net] QRM on 1296.000

I made a first real attempt today to find the source of serious QRM on 1296.000 at my location.  Fortunately, it is confined to the band 1295.990 - 1296.010 so I can do most normal EME operations except for looking for ON0EME.  I’ve made CW QSOs on .020.

I have ruled out the IF rig by using two different IF rigs, FT-817 and DSP-10.  Same thing on each.  Same place.

I have ruled out a specific IF frequency by switching the transverter from 144 MHz to 146 MHz output.

The problem is actually at 1296.000 and sounds like some electronic equipment oscillator.  But, very stable, always in the range quoted above.

First I turned off power to the house at the mains outside.  The IF rig continued to operate on its own internal battery, the transverter and LNA on an external battery in the shack.  Problem still there.

Disconnected everything on the shack battery except the transverter and LNA.  Problem still there.

Turned off the computer and everything powered from it (dongles, mouse, anything on a USB, speakers, monitor etc.) and disconnected from charging power (which was off anyway since the mains to the house were off).  Problem still there.

Went around the house removing the batteries from everything — clocks, wireless thermometers, cordless phones, smoke detectors.  Problem still there.  (It was time to change batteries in some of these anyway.)

Turned all cellphones completely off.

Then spent half an hour putting everything back together and setting all clocks that don’t set themselves and turning things back on.

As I move the dish around, the signal level and other properties changes, meaning it has some directivity to it, but there is no direction I can point, including straight up, that doesn’t see it, at about the same levels - 

I can send anyone who is interested a screen shot of the waterfall of this noise.  It doesn’t decode, of course, but is quite audible, on the level of a local beacon that decodes at about -3, on the order of 20 KHz wide.

Listening to this QRM, sometimes it sounds like it has modulation like a paging transmitter.  Sometimes it just squeals like a wall wart.

Seems likely that this is something in a neighbor’s house, hospital, or commercial transmission site.  Neighbors are tens of meters away, the nearest hospital about a kilometer.  I don’t know of any transmitters except on the hospital itself.  I do receive other QRM when I point directly at the hospital.

Has anyone experienced any QRM that was this stable and been able to determined what it was?

Thanks and 73, Courtney, N5BF
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