A lot more complicated than a Pantry Xmitter

[ppppenguin]

If you want multiple radio channels to receive in a museum environment then you can use multiple pantry transmitters fed by multiple audio sources. Seems like a simple solution to me. Though there may be a problem finding enough usable frequencies. Also more chance of upsetting somebody by causing them interference. If you're doing a setup like this you really should be using some sort of spectrum analyser (an SDR should suffice) to make sure you're not radiating harmonics.

Same with TV though you would normally use a wired distribution system. In many areas Band IV is full of digital multiplexes while Band V has been largely turned over to other users. Too much chance of interference (inward and outward) to radiate freely. Bands I and III also have other users now. Multiple modulators, with harmonic filtering if needed, can be combined using standard CATV splitters. Then a decent amplifier and split to feed as many sets as you like. I've lost touch with the Dulwich Museum setup but I think it was designed for up to 256 outlets. It's big, but hardly complicated.

At Dulwich, we have to avoid all of Crystal Palace's TV multiplexes. Even with a wired system, the high field strength means enough of CP gets in to cause grief. A DTV MUX looks like white noise to an analogue TV.