[RFI] An interesting RFI "noise" on 40 meters

David Robbins k1ttt at arrl.net
Thu Apr 23 19:24:17 EDT 2015

Exact sound is probably not all that useful... but the characteristics may
help you narrow it down when you go DF it... something on and off for 30
seconds at a time... unstable... 12khz spacing.

The 30 seconds is very suspicious... something cycling to maintain
temperature, or overheating and cycling... think about aquarium heaters,
electric blankets, or something like a lamp ballast with a bad bulb... any
street lamps flickering nearby every 30 seconds or so... check it at night
when its colder and see if it is much faster or slower, maybe give you an
idea if it is exposed to the elements.

Unstable, 12khz spacing... think cheap or poorly regulated switching supply
rather than tv or monitor that is usually more stable, again maybe a lamp
ballast, supply for led lamp, battery charger, etc.

But in any case you won't know until you go find it!

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net

-----Original Message-----
From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of Kenneth G. Gordon
Sent: Thursday, April 23, 2015 22:12
To: Rfi at contesting.com
Subject: [RFI] An interesting RFI "noise" on 40 meters

So, now I have a "new" one...at least for me. Some sort of weird-sounding,
very unstable raucus oscillation sound. Appears about every 12 kHz from 7002
kHz to at least 7350 kHz, although that is as far as I've so far tuned for

Wanders back and forth at 2 to 3 kHz while it is on, then suddenly stops for
up to 30 seconds following a slight "pop", then resumes. Seems to start out
somewhat "quiet" then build in intensity over a period of about
20 to 30 seconds.

Signal level is 10dB over S-9 throughout the entire spectrum. Normal band
noise level during the day here is S-9.

Receiver is an FT-890 in USB mode. In AM mode, it isn't nearly as annoying,
although still strong.

I have a short .WAV file of it if anyone would care to listen to it. I
cannot find anything on the ARRL's sounds of RFI list to match it.


RFI mailing list
RFI at contesting.com

More information about the RFI mailing list