Hello Hank:
I have observed this same 4 KHz RFI interference coming from wall warts,
computer power supplies and switching power supplies used for charging
batteries, etc.
They could be your own power supplies or a neighbor's. In every case - the
RFI uses the AC mains power line as an antenna - so they can be heard for
considerable distances.
73,
Tim K3LR
-----Original Message-----
From: rfi-bounces@contesting.com [mailto:rfi-bounces@contesting.com] On
Behalf Of pfizenmayer
Sent: Tuesday, July 17, 2012 9:39 PM
To: rfi@contesting.com
Subject: Re: [RFI] 4khz spaced birdies
About two days ago I started getting families of carriers spaced exactly
4 khz apart - usually in groups of about 15 -20 carriers - and the groups
seem to move 10 to 20 khz from time to time then stay there for some hours.
So far only detectable on 40 meters (two groups , one group starting at 7000
up to about 7060 and another group starting about 7132 and ending about
7176) and on 80 meters starting about 3496 and going to 3576 at the time did
not find another group up higher on 80. The carriers are very stable and I
do not detect any modulation on them - guess it could be very slow phase
change which I am not looking at . If any there on 20 it is extremely weak
and in noise - When checking , the frequencies on 80 and 40 do not appear
to be harmonically related.
The carriers are not on exact 4 khz steps - always appear to be about 50
cycles below the integer freqs. (6999.850)
I have checked on different receievers with entirely different
architecture (Orion II and Drake R7 ) and they are there on both. I cannot
find those signals anywhere in house with ICOM R10 rx and its ant held
against power lines , computers , router , TV sets ,stoves . refrigerators
,a/c etc etc etc. 40 M rotary dipole at 50 feet seems to null NE/SW but not
a deep null as I normally get so may be very close . Too damn hot to walk
street with R10 and loops right now and bum knee .
Any ideas what this might be ?
73 de Hank K7HP
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