A Neat TSCM-Adaptable Toy, And Some Crazy Antenna Theory

For those of you who have been hiding under a counterespionage rock, one of the niftier tools in the bug-hunter’s toolkit is the NLJD. In essence it’s a “non-linear junction radar” — it finds semiconductors hidden in walls and the like by bouncing a signal off them and looking for higher-order harmionics.

In the context of the NSA computer-embedded bugs (the “ANT” leaks which Appelbaum presented at 30C3) we discussed a more advanced version of this, which you build yourself… hooking up a sweep generator and spectrum analyzer, then sweeping the whole spectrum looking for odd-order harmonics indicative the NSA had tampered with your kit. (As a side benefit, this technique is reportedly far more effective than any store-bought NLJD unit.)

Unfortunately, spectrum analyzers and sweep generators are notoriously expensive… you’d be looking at upwards of 1500 units of your local currency, quite probably more like 15,000.

It turns out there may be an alternative. Just crossed my desk is a device known as the miniVNA. [1]

For under 400 EUR (plus applicable import duties if you’re outside the EU) this handy little device contains a paired sweep generator and SDR, which covers 1-3000Mhz with 70dB dynamic range.

While 70dB isn’t great, I suspect it’s probably enough to wreak some bug-hunting havoc. And, it’s both TINY and (by radio standards) cheap.

Speaking of radio stuff, here’s something to throw the RF geeks among you for a loop. Investigating the characteristics of magnetic loop antennas, a British professor came to the conclusion that “the RF capture area of an
antenna such as a half wave dipole is bigger than its physical size, because the antenna changes the refractive index of the space around it.” [2]

In other words, the antenna causes the space around it to act as a “lens,” focusing radio waves onto the antenna!

Over the course of a much longer presentation [3] this same professor proceeds to use this theory to develop and demonstrate antennas which should be impossible and unworkable by conventional theory. (Needless to say, they work fine.)

The key benefit here? Being able to transmit on HF bands without needing a massive-ass antenna.

[1]
http://wimo.de/instrumentation_e.html
http://miniradiosolutions.com/

[2]
http://www.sthost.co.uk/webspace/cats/CW%20nov%2009finalforweb.pdf ” the RF capture area of an
antenna such as a half wave dipole is bigger
than its physical size, because the antenna
changes the refractive index of the space
around it.”

[3]
http://www.ahars.com.au/wp-content/uploads/2014/05/Impossible-Antennas-and-Impossible-Propagation-Sept13-2013.pdf

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