Jim Weir wrote:

Will somebody explain to me what this has to do with r.a.IFR?
r.a.homebuilt perhaps.

Probably their best guess at an appropriate newsgroup. One of the amateur
radio newsgroups might be more help, e.g. rec.radio.amateur.antenna

-Will a wideband aviation antenna, that receives across 50 MHz up to over
-1000 Mhz, be useful for VHF and UHF TV reception as well as aviation
-frequency reception?

Useful, yes. Optimum, no.

-Can such an antenna be used by multiple devices listening to different
-frequencies at the same time?

Yes.