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Re: Topband: [TowerTalk] RX 4 square

To: "Roger D Johnson" <>,"Top Band Reflector" <>
Subject: Re: Topband: [TowerTalk] RX 4 square
From: "Tom Rauch" <>
Reply-to: Tom Rauch <>
Date: Sat, 1 Sep 2007 21:16:45 -0400
List-post: <>
> It's my understanding that, if a cable is terminated in 
> it's
> characteristic impedance, the phase shift will be equal to 
> the
> electrical line length regardless of source impedance. If 
> this is
> true, then the phase shift through the antenna matching 
> system,
> whether it be active or passive, would be irrelevant as 
> long as
> all were stable and equal.

That's true for the cables, but the source can shift phase.

This is why a high-Q antenna (one that changes reactance 
rapidly with frequency) is bad news.

It's important for the source (the elements) to have the 
same voltage into the line and there be a minimum of 
reactance shift with frequency.

Many years ago in Ohio I had loops that were not matched at 
all to a phasing system, but the array worked quite well. 
This was because the loops had such high reactance compared 
to the 75 ohm load impedance any change in reactance with 
frequency didn't cause the source to shift phase or level 
very much. That array actually became critical to tune and 
use when I tuned the loops.

73 Tom 

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