Challenging RDF target - a doubler

We have an interference source that likes to double with legitimate stations on a repeater input. There are multiple signal on the same frequency active at the same time. I am looking for advice on how to best use the Kraken in this scenario. There are effectively 3 notable sources in this case:

  • net control, transmits frequently, fixed location
  • legitimate participants, generally transmit once or twice for a small portion of the net and then are not heard again
  • the jammer, transmits frequently, and transmits over both net control and legit users. Percentage of the net transmittings varies but it can go on for 10s of minutes on and off.

Legit stations and net control follow protocol and don’t double. So generally there are 1 or 2 sources at a given time. The net control will show up frequently as will the jammer.

I am wondering if setting number of sources to 2, would be the best option in this case and let the Kraken plot the net control and jammer and ultimately toss the other signals (if heard) as noise?

Any sage advice out there?


Yep I would try setting it to two sources.

Afterwards you might need to do some manual post processing in Excel to toss out the legitimate signals if you aren’t able to turn the logging on and off quick enough.

If the interfering signal goes over the others then starting at the repeater with reduced rf gain may be worth a try. You could also get net control to reduce his tx power to aid.

We had the exact issue here in Oregon with a jammer that normally played his game during specific nets. Ironically one was the weekday 10am Technical Net. The twist we were dealing with was that he was moving along the interstate highway and we assumed it was a trucker. I have an upgraded Kerberos to a Kraken and figured I could use it. Problem was the competing signals and most were stronger than his. I reached out to this team for a way to filter or fingerprint his signal. Sadly its not there yet and maybe future upgrades will get that capability. I also own the KN2C DF2020 doppler, trying to use that became immediately useless since the doppler was spotting every signal on the input and there was no way to pinpoint which was our jammer. The good news he has been caught and recieved the FCC letter that shut him up for a few months. Just recently found out he is screwing around again in the Portland area. It took a VK3YNG Mk4 Sniffer to nail him. There were two of us using them to track him down. I have one of the sniffers in my shack attached to an Elk Log Periodic on a rotator in my attic. Being close to the highway he traveled I could follow his pass southbound or northbound and knew when he passed our overpass. The wife and I spent many hours posted along side the highway 30miles north and 40 miles south and several spots in between. If you know anything about the “Blue Box” and its automatic attenuation (audio and numerically) when you are reading a 5 you’re almost on your target. Everytime he was approaching us by watching the numbers rise somebody with a stronger signal would key up and yap, not understanding we were out hunting. By the time the jammer made noise he had passed us. The other issue was he’d take a short break and his next transmission indicated he passed us again. The repeater owner was at the right spot at the right time and picked up the 5 signal looking at a truck using his tape measure antenna. He and I were convinced he pegged him. I had a contact retired from ODOT Motor Carrier and he was able to get all the information on the guy. His delivery routes and sporadic days really complimented the jammers actions. It has been a real learning experience but the Sniffer was the answer. Feel free to contact me if you’d like any additional information. Bryant W7BDB

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I looked in QRZ and if you are the ham up in Seattle you may be in luck. The jammer down here made trips up to Seattle then over to ID and UT then back into OR coming up from the south. He’d blast the repeater on Fridays -Sundays evenings in route to his home in Portland. BTW his trucking firm is named after a popular strain of marijuana. :slight_smile: