[RFI] 160 Meter RFI

David Robbins k1ttt at verizon.net
Thu Dec 6 17:04:28 EST 2018

I would start with the smallest antenna you can hear it on from home.  I
have had good luck with a 3 or 4 turn loop about 18" in diameter, and for
closer in just the built in ferrite loopstick in a grundig g5 handheld sw
receiver.  You think NE from home so I would go N or E 1/4 to 1/2 mile, wait
for it and record a bearing and strength, then move and record them again,
get as many as far apart as you can each time it happens till you have a few
good bearings... then go 90 degrees off from where those bearings point and
try to get crossing bearings and signal strengths to refine the location.

When you get it down to a house and think it is safe to approach the owners
think about things with patterns like that, if you are in cold country maybe
a heater... is it on more often or longer at night or when the temperature
is colder?  Is it on all day or only at night?  only at night could be an
electric blanket.  Fish tank heaters cycle like that and would be less
sensitive to outside temperatures.  Maybe a refrigerator or electronic wine
cooler?  Cycles like that are often some kind of heating or cooling
equipment, not lights, tv's, computers, etc.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373

-----Original Message-----
From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of Ray
Sent: Thursday, December 06, 2018 21:42
To: rfi at contesting.com
Subject: Re: [RFI] 160 Meter RFI

Thanks Dave and everyone else who responded.
To answer your questions:
It does change sounds right at the end and sounds like a few tones before it
It seems to be on every 20 to 45 minutes and stays for 5 to 10 minutes. I
kept data all last weekend and can't see any more of a pattern than that.
It is always the same as far as I can tell It does not show up on any other
bands that I can tell but I don't think it's confined to exactly 160 meters.
I will try to be more definitive on that when I look tonight.
I am fairly certain it is not in my house. I have pretty directive RX
antennas on 160 that are pretty well decoupled and 200 feet from my house
and it is definitely strongest to the North East of my house. There are 10
or 15 houses in that general direction although I am not sure yet if that is
the area or it is further. One of those has a solar system (still not sure
why solar cells on your roof are OK but antennas are not).
I am in a no antenna HOA area but manage to put up some impressive stealth
antennas in the woods. For the recent ARRL 160 contest I managed 1228
contacts and 47 countries but could have done much better without this
I will work on hunting it down with a loop but if anyone has any ideas of
specific equipment I think it would help in my discussion with the
Thanks again & 73,
Ray K9RS

-----Original Message-----
> From: RFI 
> <rfi-bounces at contesting.com<mailto:rfi-bounces at contesting.com>>
> On Behalf Of Dave Cole (NK7Z)
> Sent: Wednesday, December 5, 2018 5:29 PM
> To: rfi at contesting.com<mailto:rfi at contesting.com>
> Subject: Re: [RFI] 160 Meter RFI
> Hi Ray,
> Trying to guess the source from looking at captures can be tough...
> That said, here are a few questions:
> 1.  Does it ever change sound?
> 2.  Does it run on a schedule?
> 3.  It is always the same?
> 4.  Is it just on 160?
> If it runs on s schedule, kill your house power at one of the run 
> times for it to test if it is in your home...
> It looks like a SMPS.  Once you get proof it is not in your home, buy 
> or better yet, build a loop.
> Look over Jim's paper, it does make a difference for the better, if 
> you follow his steps for quieting down your RF environment.
> Take a look at my page at:
> https://www.nk7z.net/sdr-rfi-survey-p1/
> That is part I of a two part series on getting to know your RFI 
> environment using an SDR.  There are several other links on the right 
> dealing with RFI as well...
> 73s and thanks,
> Dave (NK7Z/NNR0DC)
> https://www.nk7z.net
> ARRL Technical Specialist
> ARRL Volunteer Examiner
> ARRL OOC for Oregon
> On 12/5/18 9:10 AM, Ray wrote:
>  I have this 160 Meter RFI :  https://youtu.be/QI08sE2FS40 It shows up  
> once or twice an hour for 5 to 10 minutes. Any ideas what it is?
>  Thanks,
>  Ray K9RS
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