Tracking down interference with the RSP

At the Sea-Pac convention in Oregon a couple of couple of weeks ago,  Steve Brightman’s “Introduction to Software Defined Radio” presentation was immediately followed by an interesting talk by Dave Cole (NK7Z) entitled “Noise on the bands and how to tame it”.  The presentation was created by W7VO, ( and Dave himself.  Dave has many years of experience tracking down and eliminating RFI and offers the following comments:

“Over the past several years it seems I have done nothing but hunt RFI sources.  This process reminds me much of the old child’s game called “Whac-A-Mole“.  In that game, you have a playing field filled with holes.  A mole pops up randomly from one hole, and you then strike the mole on the head with a hand held mallet.  The mole is then driven back into the hole from whence it came– only to have another mole pop up from another randomly selected hole as soon as the first one is gone.  You then strike the new mole, again driving it back into it’s hole.  This process then repeats itself ad infinitum…  Locating RFI is a bit like that…

You locate one source, get it fixed, and within a few months a new one appears.  Unlike Whac-A-Mole, more than one RFI source can rear it’s ugly head at a time.  If you leave things alone too long, the RFI sources just keep popping up until you have no spectrum left.

As a free service, I do RFI locates for a lot of the locals in the Amateur Radio community via our local club.  I must admit to an ulterior motive for this– it gives me a lot of experience in tracking down RFI.  As part of a difficult RFI locate, I will do a simple site survey prior to any serious on the ground direction finding.  This helps define start/stop times, frequency, and the nature of the RFI prior to looking.  That data helps in the location process.  It further gives me a feel for the area’s RFI environment.  Having a feel for an area speeds the search process up considerably.”

Above: Twenty Four Hours of 30 Meter RFI.

We were delighted to find that Dave’s SDR of choice in his endeavors is the venerable RSP1. You can see more about this on Dave’s website here:

While you’re there check out his “I have RFI: Series”,  for a lot of useful information as well as his presentations. The home page is:

Thank you Dave, and keep up the good work!