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These are being used by the Ukrainian army for detecting incoming russian drones.

https://www.linkedin.com/posts/eyesonukraine_drone-detector-...

The firmware source is on GitHub at https://github.com/erikkaashoek/tinySA.

If they know frequency of drones (i.e. Lancet in this case) can they create something like a HARM drone, which will guide itself on source of the signal to intercept the drone itself?

A drone dangling balls of yarn...

Are they using any peculiar feature of the TinySA? From the photo it seems they're doing normal spectrum monitoring, but for that purpose a SDR dongle would work as well, For rexample the one by rtl-sdr.com. Beside being much cheaper, it can be interfaced easily with also cheap *Pi-like single board computers and operated remotely to cover wide areas. But again I have no idea if the TinySA offers any advantage over a SDR receiver in that context.

The other reply to you is buried for some reason but as they said, a hand-held battery powered unit is more convenient than something that requires a computer.

Unfortunately, the bandwidth on the RTL-based dongles is quite limited. This means that you'll only see some kHz of spectrum around your LO frequency.

1Mhz on either side but your point stands.

Portability and effectiveness. Sure, for you a dongle is great. But not if you're in the trenches covered in mud and you have to dig it out of a pocket somewhere ..

It surprises me that military drones aren't using spread spectrum to make this harder.

A lot of the drones are off the shelf drones. This war is revolutionary from a tech POV, a lot of the solutions are cobbled together -> see "cope cages"

Yeah or satellite uplinks that only transmit straight up, much harder to detect and to jam.

Is that a real thing, or a star trek reference?

A real thing: https://en.wikipedia.org/wiki/Spread_spectrum

Fun fact, the famous actress Hedy Lamarr actually was instrumental in inventing it!

You can tell GP is under 40 or they'd probably remember cordless phones "Now with 900mhz spread-spectrum technology"

Definitely a real thing. Also, during WWII actress Hedy Lamarr developed a system for spread spectrum torpedo guidance to prevent jamming, but the general idea predates that.

Yes, it’s a thing. A long time ago, my work involved a frequency hopping, spread spectrum radio link. Can’t say much about it but I’m sure that the technology has improved since then.

Hopefully its not pedantic or unwelcome of me to make the distinction between spread-spectrum and frequency hopping.

With frequency hopping only one frequency is used at once, and they're selected according to a sequence that matches a shared PRNG. As I understand it, that's what Bluetooth and some Wifi links do. They switch between discrete bands very fast.

Spread spectrum is a little different. During modulation, as with FM a series of side bands spread out. Normally we would limit these as they're considered "interference". But with the right modulator you can spread (and indeed encrypt at the RF link level) information into some bands but not others. Although all sidebands are present, to an observer who can't tell which ones carry the data at any moment, it makes no sense to even try demodulating the signal.

Neither solutions are much use if you need to communicate back because triangulation alone is enough to find you.

Curious if this tallys with your understanding, its over a decade since I had anything to so with this sort of thing. The best summary I recall was in Ross Anderson's "Security Engineering" book (first ed.)

>Hopefully its not pedantic or unwelcome of me to make the distinction between spread-spectrum and frequency hopping

Spread spectrum refers to any technique where a narrowband signal is deliberately spread to occupy a larger bandwidth.

Frequency-hopping is an example of a spread spectrum technique; they're not different things. Direct-sequence spread spectrum (which is what I think you're describing) is also a spread spectrum technique.

There are also other techniques; the most popular one is probably the chirp spread spectrum as used in LoRA.

Thanks for the clarification NW

No, it’s fine by me. I believe that it was thought that the combination of frequency hopping and spread spectrum would make it difficult to monitor and jam ( other than very wide band jamming). My application was rapidly moving so triangulation would be difficult.

If I understand the capabilities of modern Software Defined Radio systems, then they can monitor many different frequencies at the same time which might defeat those old systems. It’s been a long time since I read up on the current ideas and capabilities.

> If I understand the capabilities of modern Software Defined Radio systems, then they can monitor many different frequencies at the same time

Haven't been keeping up with it as much as I should, but that's very interesting.

Isn't good old cdma a spreadspectrum technique, used for cell phones back in the day from quallcomm?

Yes, one of the four basic types. CDMA is the Direct Sequence Spread Spectrum variant.

https://en.wikipedia.org/wiki/Spread_spectrum

Spread Spectrum is very real, it was used in 802.11b.

Yes and Bluetooth.

In those cases it's not used to make detection harder though but to be more resilient against interference.

This might have to be my next DIY project...

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