Coff,
Thanks. I hadn't heard of the PV141 before and while I was looking it up, I saw that the PTR170 UHF set was also a stand-by radio for other aircraft. I hadn't realized that.
It still amazes me that limited-channel crystal-controlled sets were still being produced in the 60s. The technology for frequency-synthesized radios had been around for a while and could have been used to produce a much more flexible radio.
I remember having a conversation with the tower at Syerston, trying the convince a very surprised Air Trafficker that even though I had a UHF radio, I could not change to her Local frequency and would have to stay on 362.3 (sad that I can remember that, I know).