"As for the frequency-hopping being tracable by direction finding, it's designed to be random noise digital signalling. so to direction find it, you'd need to know the FSK OTP already to differentiate it from the background."
Nope.
Radio communication contents can be digital if desired, but the physical electromagnetic radio transmission wave itself is always analog.
Look up at the stars tonight. Some of those stars transmit radio waves (which are analog by definition) at seemingly random frequencies and times.
Yet a typical college astronomy student can sweep a spectrum analyzer over any such star and quickly see on an oscilloscope the "random" frequencies on which the star is emitting radio waves.
In fact, the student can sweep the spectrum analyzer over black sky to "discover" stars that aren't even seen.
Now, does it matter if there is data digitally encrypted/encoded on any of those radio frequencies/waves? Not for the purpose of discovering the direction of said transmitter.
...
Pause
...and likewise, such digital encryption matters not to a DF team...said team being interested only in the fact that your antenna is emitting energy.
Energy can be tracked. That's what DF'ing is all about.
And if you are moving, then the directional antenna that is tracking you won't even care about background noise. Won't matter.
Likewise, changing frequencies will change where on the spectrum your energy is detected, but it won't change the fact that the energy you are emitting is being detected.
And if two antenna's detect your radio transmission frequency, then it becomes a simple matter to determine your location.
Ok, I guess I need to spell this out.
For any given microsecond, the frequency choice is between two frequencies previously assigned via a One-time use ROM chip. If there is a signal on one, it's a '1'; if there is a signal on the other, it's a '0'. The ROM is programmed easily by an antennae tuned to your favorite random number generator, the universal background noise.
So, there is no "signal" to find. The power used is trivial, and looks like noise. Even a Direction-finding antennae needs to be tuned to a band; it can't just listen to everything. It would end up pointing at the nearest broadcast station.
It gets a bit tougher when they jam, since then the operator has to activate a higher power mode, which might be descernable in a rough way. But then their jammer also would be on the same band that they are trying to DF, with the result being finding the jammer.
Now, if you are quite through with mincing words and trying to sound like you know something, you can go crawl back under your rock.
However, this digital system is the newer one, I'm not at all sure the Israelis had it in field. But it's simple enough that It would take less than 50 man-years to develop from scratch.