[BC] Diplexing an AM antenna.

[Wayne]

Ron::

A diplexer is series resonant at one frequency and parallel resonant on 
another with the mirror image on the other transmitter.

Several things you must be careful of,   The circuit Q's should be matched 
between networks, and the bandwidth of both channels should match.

Tall towers do not diplex well without a secondary network to ground.

A single stage diplexer has no ground reference.  The Diplexer comes after 
the matching network, and attaches to the tower.

Just a bit of information.  Good Luck

Wayne Woollard
----- Original Message ----- 
From: "Ronald J. Dot'o Sr." <ron.doto at comcast.net>
To: "The Brain Trust" <tech-assist at radiolists.net>; "Broadcasters' Mailing 
List" <broadcast at radiolists.net>
Sent: Monday, April 30, 2007 7:51 PM
Subject: [BC] Diplexing an AM antenna.


> Hi Gang,
>
> I'm about to take on a job I've never done before and would be grateful 
> for any advice.
>
> I'm under the impression that a diplexer is like a double ATU with filter 
> traps to couple each station to the tower while rejecting the other 
> station from the respective transmitter's output.
>
> Is it very different from tuning a single ATU for each respective station?
>
> Any suggestions on who to get the diplexer from?  Do they usually provide 
> detailed tuning instructions?
>
> The frequencies are 1220 and 1490, both 1 Kw. class C's.  I don't know 
> what the tower resistance is yet.
>
> Thanks for any help,
>
> Ron D.
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