"Avery Fineman" wrote in message
...
In article ,
"Larry
King" writes:

"J M Noeding" wrote in message
...
......
You seldom see such large dimensions, believe they had
waveguide for the over hoizon radio link system on 900MHz, but usually
WG is not practical below 3.3GHz .......

Nonsense, rectangular waveguide is used quite frequently in UHF
television
broadcast transmitting installations. Granted it's pretty good sized
stuff
to get the lower cutoff frequency down where it needs to be in the 450 -
800
MHz range (WR1150, WR1500, and WR1800 for example) .. at least 6" x 12"
outside dimensions. But it's definitely practical at those frequencies
which are far below 3.3 Ghz.

Rectangular waveguide below 1 GHz (which is above UHF TV)?


Sure, take a look at the URL in my original message from the Dielectric
webpages :-) And the Andrew Corp. extolls the virtues of its circular
waveguide product line for the same application.....

http://www.andrew.com/search/docviewer.aspx?docid=398



Coaxial structures, yes, especially for the visual-aural diplexer.
I've walked INTO the channel 13 diplexer for KCOP on Mount Wilson
(serving Los Angeles with 50 KW into the antenna). Just open the
door in the corner formed by the visual and aural transmitters and
one comes upon a massive array of round structures...:-)

When I first read this, I though you meant that you were ***inside*** of the
diplexer [hopefully not while it was 'on the air'] :-) Then I reread it,
and understood what you meant. Yes those coaxial cavities can be quite
impressive.

73s