[ztetranz]

I think that's a phasing device. You attach an auxiliary antenna specially to pick up the noise. The signal from that is phase shifted and mixed into the signal from the main antenna. The phase shift circuitry has knobs to vary the phase and amplitude. You adjust them so that the noise cancels out.

That can be effective but it's really only useful for cancelling out one noise source. I once used a similar device when there was something bad happening on a power pole down the street. It's no use if you have general noise from multiple directions.

[aaomidi]

This would be an effective method against Iran’s scrambling of satellite TV