[RFI] Broadband RFI...

Frank N. Haas KB4T utility.rfi.pro at gmail.com
Tue May 31 09:54:08 EDT 2016

A few years back I investigated a broadband source that was noticeable from
1 to about 10 MHz. It turned out to be a privately owned device...the
actual type of device won't be mentioned because what is important here is
the search and not the result. Suffice to say the source was a power supply.

When the complainant demonstrated the problem all that could be noticed was
an elevated S meter reading and a high pitched tone whose pitch didn't vary
anywhere the receiver was tuned between 1 and 10 MHz. If one just listened
to the receiver one would think everything was normal. In reality the noise
floor hovered around S9 to 15 over.

Searching for an elevated noise floor is challenging but not impossible.
Every source has a unique characteristic of some sort. In some cases, the
unique feature can be seen on a receiver scope i.e. Radar Engineers Model
240 or equivalent. In others it may be some aural feature. The search then
becomes a hunt for the location where the signal with the unique feature is

In the case of the broadband source I chased, I had to listen carefully for
a few minutes to learn all of the unique qualities of the source. I ended
up doing an expanding circle search which brought me to the source.

Good luck.

Frank N Haas KB4T
Utility Interference Investigator

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