I lot of broadcast operations have a frequency that isn't in the broadcast band that they use to send their signal to a remote tower. Presumably if you point a stronger transmission at the receiver you can become the dominant signal. Or at least that's what I always thought. I would think you would have needed some inside information or otherwise have worked in the industry at the time to really pull this off? Maybe not, though.
So hijacking it would not be trivial. You need to be in the line of site and be able to produce enough power to overwhelm the real signal, which isn't trivial at those frequencies. There's also probably something similar to ATIS to stop unauthorized transmissions.
Here's KIRO uplink from their studio to a tower atop Queen Anne Hill in Seattle. The exact location of the transmitter and receiver are in the locations tab.
> ...hijacking it would not be trivial. You need to be in the line of site and be able to produce enough power to overwhelm the real signal, which isn't trivial at those frequencies.
-While power at 10GHz is non-trivial (though significantly less so now than in the eighties!), you can cheat by being closer to the remote tower than the official source, as received power is reduced by the square of the distance from the transmitter.
You can find "lobe diagrams" for common antennas. You just look at the angle that the receiving point is at in relation to the transmitting antenna in the lobe diagram.
There is no mention of the read broadcast being overlaid by or fading into the attackers signal, which I would expect if they were pointing an antenna very carefully to maximize their attack.
Instead, I think someone physically unplugged a signal cable somewhere and plugged in their own feed. Possibly even an insider.
-Just wagering a guess here - the link was probably frequency modulated; an FM receiver has a very strong capture effect - the strongest signal received on the tuned frequency is the only one demodulated; any other, weaker signals are effectively just raising the noise floor.
Smaller antennaes needed for the same gain as lower frequencies.
Terrible ability to go through, say, a concrete wall, but that’s an issue for broadcast, not point-to-point. Possibly an advantage by reducing noise from other 10ghz signals (maybe harmonics from a bad microwave oven?).
They also have narrower fresnel zones than lower frequencies, so it’s easier to hit your target without having to be too high at both sides.
And the usual tradeoffs: Spectrum is available and you want equipment that’s cheap and reliable, but not too cheap either.
That's a good question. Thinking of the paths I usually see them take though, I think the beam would always be too low. They'd end up both too close to the tower and too close to the ground.
The Wikipedia article seems to indicate even the engineers never figured it out.