The following article – written by Roger G3SXW - first appeared in the May issue of CDXC Digest, and is reproduced here with the author’s knowledge. We believe a wider audience should read this most insightful tale into the nasty world of DQRM – and how one particular individual was literally caught in the act. Download the article (pdf format)
I worked in Signal Intelligence in another life (about 50 years ago) and the tracking of this DQRM character strongly resembles what we did to find certain Bad Guys when certain Bad Guys were our enemies (and some still are). Very good work on the ham's part. We could find someone within five miles from a distance of 300-500 miles. Not bad for vacuum tube technology. Not only that, we had RFP capability too. I really like to read success stories like this! Too bad we have to do it, though.
I wonder if it would be possible to implement the wide-area DF function in near-real time. If you can imagine something like a DX cluster site (this would be a DQRM-cluster site) where you would go when you heard intentional interference during your operations... You would enter a report consisting of: 1) Your call 2) Time/date of incident 3) Optional lat/long if you were mobile or portable (not at your home QTH) 4) Observed S-meter reading of QRM 5) S-meter reading of an 'empty' frequency on that same band and time. The data obtained would be crude, but the number of possible reports would be HUGE and it might be possible to process the data of 100+ crude reports (as opposed to 3 or 4 calibrated station reports ) and get something usable. Just a half baked idea...
Interesting idea! We used what we called a Flash Net to alert our guys to listen on a freq for the Bad Guys which is virtually the same as what you're proposing.
It is certainly feasible to DF signals to specific locations, not tricky at all. The trick comes in the manpower to do so, the large number of sources, correlating each signal with each source, not impossible but very resource intensive, given the near random time and frequency of the offending signals. Suppose all these obstacles were overcome, and a definite perpetrator identified with specific, detailed, recorded acts of DQRM. Now what? When I was involved in tracing 2M jammers on a San Diego repeater system a couple of decades ago, there wasn't much one could do. The FCC would not base an accusation on evidence gathered by non FCC personnel. Confrontation seems risky on several fronts. Publicizing the information can lead to expensive and demoralizing legal entanglements and aggressive self help is likely to result in crimes being committed, essentially becoming vigilantes. There, over a long period of time, we were able to develop a relationship with the FCC personnel to furnish to them DF info we collected. It took a long time to establish our bona fides, that we were capable, able to gather and report accurate, reliable useful info, and were not on our own vendettas, etc. The FCC then had that intel to aid in its own monitoring activities. This eventually resulted in a couple of revocations, show cause orders, a few warnings, etc. It was successful only because of the enthusiasm, persistence and malevolence of the perpetrators, the relatively small geographical area, the concentration of DQRM to one repeater system primarily, and some luck, which luckily we were prepared for when it happened.
Goal was reached, he stopped, great work by all and a great report. Buttttttttttt I would have hung him out to dry. Just my nature. Adios
One of my professional specialties is direction finding and interference hunting -- I've done quite a few whitepapers and webinars/seminars on DF, including doing a workshop last year at the VA Tech Wireless Symposium and will be a panelist at a NIST conference in a few months. I also have done a lot of field work tracking down interferers. I come across a very disproportionately large number of amateur radio operators in my line of work: some of the best (professional) DF and interference hunting folks are hams in their spare time, and I'm sure this is no coincidence. Excellent (team)work on this case, especially given they were not using "professional" tools (which are well, well out of financial reach of most hams).
From the article: "A well-positioned radio amateur DXer is employed in UK with access to professional DF facilities. He joined our small, ad hoc investigative group and was permitted by his employer to track EASSYL when not otherwise engaged in his professional duties. This facility is extremely accurate, determining a heading to within two degrees azimuth and may simultaneously take automated bearings from several different sources (countries). The headings are automatically drawn on a map and the lines converge on one point, indicating the location of the signal within the range of a very few miles. This facility was used, during 2014, to help locate EASSYL. " The "well positioned radio amateur" worked at Baldock Monitoring Station which is the government monitoring station for the UK. http://stakeholders.ofcom.org.uk/binaries/enforcement/spectrum-enforcement/baldock.pdf
I've visited this facility and provided training to them as well (some of Ofcom's DF equipment is made by my company), so I'm somewhat familar with their DF capabilities. The really impressive part was the local Italian team that had to narrow down the precise location of the transmitter: "In the car was a receiver but with only three feet of wire as the receiving antenna". I've done a LOT of similar direction-finding as part of my job (looking for actual sources of interference), but even with a profesional portable monitoring receiver and antenna (PR100 / HE300) it can sometimes be a challenge. Finding the station with a "normal" receiver and a few feet of wire is pretty impressive.
I would think with HF pinpointing a signal coming from a specific antenna would not be impossibly challenging, once you got within a mile or so. For one thing, it is not often as though you are looking for a clandestine radio, like the SOE or CIA might be using. A great many of these bozos are DXers with high power and large prominent antennas. The big challenge might be arranging directional antennas that are mobile/portable. Timing is the challenge since you usually cannot predict when the offender will be active, or when he will suddenly stop, often maddeningly just as you get close. My transmitter hunting was all at VHF-UHF, with ordinary amateur gear, modified to reduce sensitivity as you got closer, and a 3 el yagi sticking out the window or sunroof. Not many jammers were running high power either. That was ~35 years ago. I can imagine the state of the art has progressed significantly since.
