[RFI] New RFI source for me...

Frank N. Haas KB4T utility.rfi.pro at gmail.com
Sun Jul 24 11:36:41 EDT 2016

I will not speculate as to what the source might be. As I have said in this
forum many times, I consider such attempts to be a complete waste of time.

However, I will say that the periodic character of the source should make
it easier to find. If the highest frequency at which this source can be
detected at your location is 4.0 MHz, options are limited. The first tool I
would use is a battery operated receiver and the National RF HFDF Vector
Gun active loop antenna kit.

You don't describe the antenna or radio equipment being used to hear the
source. You also don't describe the  relative signal strength though from
the audio recording it would seem that the source is fairly strong. It may
be difficult to hear the source on any portable receiving system. If so,
you may have to perform an expanding circle or square search to find a
location where you can hear the source well enough to begin pinpointing it.

I have been faced with this kind of source many times over my RFI
investigation career. Patience, good record keeping, more patience and an
open mind are essential.

Don't waste time trying to guess what this source might be. Find it. Then
report your findings.

Each time one is involved in a search of this sort, the experience is
valuable, educational and, when successful, very satisfying.

Good luck and good hunting.

Frank N. Haas KB4T
Utility RFI Investigator

On Sunday, July 24, 2016, Dave Cole <dave at nk7z.net> wrote:

> Hi,
> I have had a new RFI source pop up here in the past few days...  It
> appears to be on a timer, running at night, but does not sound like a
> lighting system I am familiar with.  It starts about 8:30 PM, and ends
> at about 8 AM the next morning.  It is quite odd from my prespective, in
> that I have never heard one like this before...
> Audio is here:
> http://nk7z.net/wp-content/uploads/2016/07/2016-Jul-24-14-13-38.mp3
> Anyone ever hear something like this?
> It appears to cover 1.7 MHz., to about 4.00 Mhz, and I swear, it rolls
> off to protect the AM band.  It reminds me of one of the Ethernet over
> power line devices when I look at it with a Spectrum Analyzer.  The
> signal looks to be rolled off starting at 1.7 MHz., and gone by 1.6 MHz.
> Anyway, any suggestions as to what it might be would be helpful to me in
> locating it.    My mobile antenna is under repair at this time, so I am
> doing my homework prior to a locate run.

Frank N. Haas KB4T
Utility Interference Investigator

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