Just tracked a randomly selected transmitter using the Kraken SDR, and it only took about 10 minutes of driving. This is classic “fox hunting” in the amateur radio community: a longstanding direction-finding sport that pits operators against each other in locating hidden signals. Yet beyond the fun, it delivers... a sobering real-world demonstration of how rapidly any transmitting station can be located the moment it keys up. The Kraken SDR achieves this with a compact circular array of five evenly spaced dipole antennas connected to fully phase-coherent receivers. All five channels share a common high-precision clock source and run continuous calibration to maintain synchronization. As the incoming RF wavefront reaches each antenna at microscopically different instants, the system measures the resulting time-of-arrival differences (equivalent to phase shifts across the array). Using advanced correlative interferometry and the known physical geometry of the antenna placement, it computes the precise direction of arrival (bearing) in real time and overlays it directly on an interactive map. Mitigation techniques are essential if you wish to minimize your detectable footprint: transmit at the absolute lowest effective power required, limit yourself to extremely short bursts, employ directional antennas carefully oriented away from potential listeners, implement frequency agility or hopping patterns where feasible, and, when operational security demands it, maintain complete radio silence. In today’s environment, understanding and managing your RF signature is no longer optional.show more

How accurate has it been to just get LOB from a fixed position? Have you messed around with locating meshtastic nodes at all?

The accuracy of obtaining a LOB from a fixed position using the KrakenSDR has proven to be quite good, typically within 8 degrees under favorable conditions. That's a good enough level of precision for effective direction finding, especially when multipath interference is minimal and the antenna array is properly configured. Combining bearings from multiple locations while driving substantially improves overall geolocation accuracy and typically pinpoints the location fairly quickly. Regarding Meshtastic nodes, I have not yet attempted to locate one. However there are no fundamental technical barriers to direction finding one of these devices with the KrakenSDR. Meshtastic operates primarily in at 915 MHz (in the U.S.), using low-power, intermittent LoRa transmissions. I’ll have to try locating one in the future, but will need to construct a 915 MHz dipole antenna set first.

Are you swapping antennas on the array to target specific signals or does it use something more like a wide band scanner style antenna. I want to get a kraken sdr sometime this year hopefully.

Two or more of these units at stationary locations can link up and triangulate a transmission instantly. I have not done it but I hear it works a peach.🍑

I have two units but haven’t tried this yet.

Should work good for habitual kerchunkers. You can just answer them by name and say their kerchunk hit the repeater loud and clear. 🤣

In other news, I wonder how big of a baseline could be achieved… for amateur radio astronomy purposes. Early in my career I did long baseline interferometry for NRL, then a few years later I spent some time at NASA Goddard helping measure continental drift via VLBI. So I ought to be able to handle the math.

Such like you had an interesting career! For VLBI on using the KrakenSDR (or any amateur SDR) each site could use external references disciplined by GPSDOs to synchronize clocks. However, phase stability would likely remain a significant challenge. It would nevertheless be fun to explore.

Is this similar to wardriving?

It bears a superficial similarity to wardriving in that both involve collecting RF data from a moving vehicle. However, they differ fundamentally in purpose, technology, and target signals. Wardriving refers to the practice of searching for and mapping Wi-Fi wireless networks. In contrast, radio direction finding employs coherent multi-channel reception and phase-based algorithms to determine the precise bearing of signals to triangulate the location of active transmitters.

Could you hard mount a similar antenna pattern on a truck for long term utilization? Pic for reference

Absolutely. I’ve see government vehicles setup like this. Some police vehicles also have this for locating LoJack on stolen vehicles. As a side note, the Starlink Mini is much harder to radio direction find because its phased-array antenna creates a very narrow transmit beam (typically 1–2 degrees wide) steered precisely upward toward an overhead satellite, concentrating power skyward while severely suppressing off-axis emissions. This results in drastically reduced signal strength in most terrestrial directions, often below reliable detection thresholds, and uplink bursts are short and adaptive under strict power control, limiting coherent signal availability for accurate bearing estimation.

That’s so cool. I’d love to learn that shit.

It’s fun and not hard to learn.

@cemaxecuter I love it and I want to get your form factor down and increase portability!

@cemaxecuter Me too. Haha. At the moment, I basically have all the hardware thrown into a box. I will eventually get everything mounted with external connections for the antenna and power.

@cemaxecuter I have a mad box of cables and hot glue. You are far more refined, sir

@cemaxecuter Sweet

Kraken SDR 😍

I literally was having a X argument 2 months ago, the guy was saying this couldn't be done and I was like oh yeah it can, and it's here now

If your transmitting you can be found.

Yep! not just overtly transmitting. Even "just receiving" there are LO's and other clocks running that radiate.

Setup a scenario where you have multiple transmitters (6+) transmitting intermittently and not more than 1 transmitting at a time. Have fun! Lol

One effective approach to this scenario involves deploying two or more KrakenSDR units at known locations separated by a suitable baseline distance. Each unit, equipped with its antenna array, would independently determine the direction of arrival (bearing) toward the active transmitter whenever one of the six or more sources transmits intermittently. Since only one transmitter operates at any given time, the system captures a clean bearing from each KrakenSDR during that brief transmission window. The intersection of these bearings, typically two or three for reliable triangulation, provides an estimated location of the active transmitter. This method leverages the KrakenSDR’s built-in correlative interferometry capability for accurate single-unit direction finding, while multi-unit coordination enables precise geolocation without requiring phase coherence across distant sites. The KrakenRF RDF Pro software and cloud-based mapping tools provide this exact capability, combining bearings from multiple distributed units (fixed or mobile) to achieve near-instantaneous triangulation, even for intermittent signals. I have two of these units, so I will need to set this up at some point to give it a try.

That’s amazing!

I did fox hunting with my Dad (G4 BPC) in the late 70s, great fun with much skullduggery when we were the fox. Happy days.

My dad was never into it, but sounds like it must be some great memories.

kool

Awesome tech.

I worked on DF equipment back in the day (P/F/T DOA) so I know this works. But maybe not DFing a large fixed radio tower in the demo video would better get your point across 😂

I just picked a random single but fair point.

Is it just one receiver or can you define multiple? Curious how many targets you can track simultaneously

Love this shit right here. Wish I had time to deploy my old setup

All hail the classic war drive!

705 best

NVIS transmitted from a valley might be a bit hard to track, too?

2 years ago I almost purchased the older model. The one with the multi antenna array. Real good shape but he wanted what they had been asking on eBay. Still on my most wanted list but after seeing this I might do some more homework. This looks like a lot less gear.

It’s not a large amount of equipment. The setup primarily includes the KrakenSDR, a compact computer (such as a Raspberry Pi), and antennas. Small extendable antennas with magnetic bases work well for this purpose. Magnetic mounts are not feasible on the Jeep roof, so I recently upgraded to dipoles and constructed a dedicated base.

Love my SDR

This sounds like an improved version of Lo-Jac. Also like a doppler shift, but analyzed in the radio.

Everyone gets a RC-135 in their pocket nowadays

Quite educational

Don't forget time delay and remote operation as ways of mitigating risk to the operator. A raspberry pi and a python script can make it trivial to send a message once the op is clear of the point of transmission. Gear can be picked up later or replaced.

Why do all radio fags have receding hairlines?

trawling fishing

This could have been simplified to just say, wave come in, circle of antennas can see where wave hit first and get direction of signal

what does a kraken setup like this cost all included?