Andrew Heliax is fine cable - just what you need to run
up a tower (it comes in many sizes). But in an airplane?
Like the man said - it's overkill. I'd recommend RG142.

As for the isolation - engineers have an inside joke that
goes something like this:

Oh say can you see.....
Three Hundred Dee Bee....

This is a range greater than that between the smallest
detectable signal to an unimaginable amount of power.
In other words, it doesn't exist in the natural world.
AFAIK, nobody makes anything with "300 dB of isolation".
Any engineers out there who would care to comment?

David Johnson