[RFI] How far does RFI travel?

Scott Yost nm8rmedic at rocketmail.com
Tue May 10 20:27:09 EDT 2016

Like most absolutes in life, this one is not absolute.There is a device which you MUST track by itsnoise signature – the Sling Media Homeplug Ethernet device.  In Europe it is called PLT.  

It uses a homeowner’s house wiring – and thewiring of every other home sharing the commercial power distribution transformer – tobroadcast its ‘wifi’ signal.  A singleunit, in one home, will radiate from every foot of wiring in every home on thesame transformer.   DF’ing one with my National HFDF showed signal –everywhere.  There were peaks and nullsof course, but it originated from every home and outbuilding with AC wiring.   Since it is an HF signal and by design has no VHF component,going higher in frequency to precisely resolve its location is notpossible.  You have to describe thedevice to the homeowner, and then find it by a hard search.   I have samples of its audio (RF) signatureif you encounter this beast and want to shorten your time spent in locatingit.   Description: repetitive at approximately a 2 secondinterval.  Fairly regular.  It sounds similar to an electric fence, butunlike electric fences, it is very frequency specific.  No RFI > 25 Mc.  It is notched to avoid the amateur bands, but blankets the 19meter and other higher and lower SW bands. Also there is no component in the AM BCB. What my National HFDF unit did locate, was a pair of arcingAC power connections in the attic of my neighbor’s home.  We found the Sling unit almost by accidentwhile killing breakers to repair the arcing wiring.   
I am not a professional RFI investigator.  Just a poor dumb engineer.  

    On Tuesday, May 10, 2016 1:48 PM, Frank N. Haas KB4T <utility.rfi.pro at gmail.com> wrote:

 While extreme, the last example should be adequate proof that there is no
predicting how far RFI CAN or will travel.
I categorize this question in the same manner I categorize questions about
what a source might be by the recorded sound of the source. That is,
speculation about the nature of a source may be entertaining but it serves
no other useful purpose.

Each case is unique just like every other case. Time is best spent choosing
the best method for locating the source followed by actually locating the
source. Whether the source is 100 feet or 100 miles away, once it is found
all questions will be answered.

For the billionth time: RFI is not pinpointed with eyes or ears alone. Good
equipment ("tools") coupled with proper interpretation of the data provided
by the equipment will lead the investigator to the source. Guessing what a
source might be or how far away it might be is a fruitless waste of time.

It is my opinion that the primary message here should be: *Find it first.*
The answers will then be apparent.

Frank N. Haas KB4T
Utility RFI Investigator
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