[RFI] 40 M QRN

Dale Martin kg5u at hal-pc.org
Wed Feb 11 19:59:56 EST 2009


Have you turned off all power to your house to confirm the noise is not from

Also, you might want to drive around--the noise may be coming from farther
away than you think.  

I had an intermittent noise that drove me batty on all bands from 10 thru
80.  I finally found it over a mile across the subdivision -- it was a
doorbell transformer in someone's attic.  Once I zeroed in on it, I asked
the owner if he was seeing noise on this TV - he was.  I told him it was by
his transformer arcing internally and that it was a serious fire hazard.  I
let him listen to it on my 2m HT -- it broke the squelch.   The noise was
gone by the time I got home. 

Hope your as successful. 



-----Original Message-----
From: rfi-bounces at contesting.com [mailto:rfi-bounces at contesting.com] On
Behalf Of Ash Thornton
Sent: Wednesday, February 11, 2009 2:30 PM
To: rfi at contesting.com
Subject: [RFI] 40 M QRN

I have been watching the various discussions, but not sure I have seen the
situation I an experiencing.

I notice a very wide band QRN situation which is very noticeable on CW with
a 500Hz filter, usually S 3 spanning up and down the spectrum. It often
rises to S 5 or S 7 for short periods. On AM it is a very fast buzzing
noise. I use a 4 Square and usually it is from the south, but not always. On
a horizontal it is also there and same directions.

It also shows up on 80 M, but the noise is higher there and I do not operate
as much 80 CW.

After dealing with this for several years it makes me think it could be a TV
as the times could mirror watch TV at breakfast and the even and more so on
the weekends. Certainly could be something else. I have had not luck trying
to pin it down with an Icom HF handheld, does not register on the Icom.

The noise blanker does not affect this QRN. Taking out a preamp helps a bit.

Not sure it is the same noise, but at times it appears to roll down the
band, at least by tracking it on the S meter. Sometime sthe noise sounds
like a carrier on AM, could be a different source.

I am looking for ideas given walking around with the small HF receiver does
not show anything?


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