Comms Boy, Tigersaw and Scot Cabin, thanks for all the info and suggestions, all taken in ....
re: the computer comment, as Scot Cabin said, a lot of the RF stuff is still getting down and dirty with electronics.
Superhet was a great suggestion, will definitely be brushing up on that.
In the first stage assement there were questions on propagation, modulation, circuits etc...
AM demodulator was one of them (the simple diode, with the CR circuit)...
but they had 2 or 3 questions on scenarios where there was a faulty component and which do you think it was and why, so wouldn't surprise me at all if there were more of that asked in the interview.