On 07/02/15 17:24, Jeff wrote:

Very true. Weren't there all sorts problems later on when some of our
emergency services got radio, and some areas used and AM, and some
used FM?

Even in the areas where the police used FM they were required to have
one AM channel for compatibility (on VHF). Some of the later police
mobiles were capable of both AM or FM on a channel by channel basis.

Really? The only ex-emergency service radio I've seen with AM and FM was
the 'Whitehall' which, if memory serves, was a Low Band unit and useful
for 4m. I repaired on once, quite a beast, with a mass of cables to
connect the boot unit to the control box.

Later radios tended to be pretty standard PMR sets from the likes of
Storno.

The 'Met' police did have a mix of AM and FM radios at one time but they
were different units. I think the AM sets were around 150MHz. FM was
just above 2m and UHF (450 or 460 ish). I think the cars, especially
those on traffic, used AM. Certainly the personal radios were UHF FM. I
knew someone who worked in the Met comms side.

I recall a major fire locally in 1990 or so when the police and fire
couldn't talk to each other at all via radio. In the end, they had a
couple of RAYNET people relaying messages between them, one was with the
senior fire officer the other with the senior police officer. The police
didn't even have enough radios for all of their officers and relied on
RAYNET.