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Re: [TowerTalk] Stacking tribanders (SteppIRs)

To: "'Terry Gerdes'" <>, <>
Subject: Re: [TowerTalk] Stacking tribanders (SteppIRs)
From: "Joe Subich, W4TV" <>
Date: Mon, 31 Jul 2006 11:14:19 -0400
List-post: <>

Look carefully at the design of ANY stacking switch.  Many use a 
single fixed 2:3 turn radio autotransformer  (2.25:1 impedance 
ratio) as a compromise for both two antenna and three antenna 
stacks.  In a 50 Ohm system this results in "best case" SWR of 
1.13:1 with two antennas and 1.33:1 with three antennas.

There are techniques that will allow proper matching (switchable 
taps or multiple transformers) with either two or three antennas 
however, they are more expensive than the compromise designs. 


   ... Joe Subich, W4TV 
       microHAM America 

> -----Original Message-----
> From: 
> [] On Behalf Of Terry Gerdes
> Sent: Monday, July 31, 2006 10:05 AM
> To:
> Cc:
> Subject: Re: [TowerTalk] Stacking tribanders (SteppIRs)
> Hi Howard,
> Thanks for the replay.  Does the Comtek switch work better than 
> the Stackmatch?  What I see here is the lower and mid antennas 
> have flat SWR when running standalone but when I put them into a 
> stack, the SWR jumps high enough to get close to dumping the Alpha 
> amp off-line.  Does the Comtek switch provide a better match?
> Terry


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