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Re: [TowerTalk] Coax Lengths for Stacked Yagis

To: "Richard (Rick) Karlquist" <richard@karlquist.com>, towertalk@contesting.com
Subject: Re: [TowerTalk] Coax Lengths for Stacked Yagis
From: Wes Stewart <wes_n7ws@triconet.org>
Date: Fri, 4 May 2018 13:07:32 -0700
List-post: <mailto:towertalk@contesting.com>
I probably should have been a little more specific; there are some special case exceptions.

Roy Lewallen says on page 6-15 in my 22nd Edition of the ARRL Antenna Book:

"The only cases in which the current (or voltage) delay is equal to the 
electrical
length of the line are
1) When the line is flat; that is, terminated in a purely
resistive load equal to its characteristic impedance;
2) When the line length is an integral number of half
wavelengths;
3) When the line length is an odd number of quarter
wavelengths and the load is purely resistive; and
4) When other specific lengths are used for specific load
impedances."

Wes


On 5/3/2018 9:24 PM, Richard (Rick) Karlquist wrote:
Isn't it true that for lines that have a length
that is any multiple of a quarter wave,
the phase shift when matched is the same as when mismatched?

Otherwise, (1) is correct AFAIK.

Rick N6RK

On 5/3/2018 9:06 PM, Wes Stewart wrote:
Another point or two and then I'll shut up.

1)  The expected phase shift in a line is only achieved when the line is matched.

On 5/3/2018 7:28 PM, Wes Stewart wrote:
Quarter wavelength lines have the magical property that the output current is equal to the input voltage divided by the line Zo.  So with multiple inputs tied together, and obviously having the same voltage, the output currents will be equal.


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