On Wed, 27 Jan 2021 10:16:22 -0000, "Brian Gaff \(Sofa\)"
wrote:

Yes but he presumably meant dab and FM, presumably the latter as the
modulation type on digital is more complex and a lot more powerful due to
the duty cycle.
After all you are just sending a movable blank carrier on fm, more or less.
I think they probably my use travelling wave tubes at uhf though not sure
about the dab as that is band 3.
With regard to Long wave, there are whole transmitters around I think that
could be used at those low frequencies, but its true, the more specialist
the valve, the less likely it is to be available against when everyone was
using them. I'd imagine the low end of Medium wave type transmitters use
similar devices but the current Long wave transmitter is much higher power
than most of the medium wave outlets.

Is the valve used specific to the frequency transmitted or could we
buy valves from long-wave transmitters that are closing down?