Third attempt ... successful.
I'm not sure if this is common for 79 series land cruisers but I found I could not remove the aerial and rope without hot wiring the aerial motor. You see, once the aerial securing nut was removed from the guard and when using the aerial switch in the cab, the aerial would only extend to the height of the aerial, and would not "unwind" the rope further!
So, hot wiring the aerial motor overcame what was happening to me.
My first attempt I wasted about 2 hours :(. I had bought a complete aerial, motor and all. I removed the auxiliary battery, disc connected all there associated wiring, removed the batter carrier, removed the aerial as much as I could then I thought I'd better sus out the female end of the coax (at the head unit).
Bgr me. The female receptor was as I expected, a round receptacle. The male connector, part of the coax and attached to the aerial, was square, doh!#. Re-assembled everything for a very disappointing experience.
kennym