[Top] [All Lists]

[AMPS] Hold on - SWR meter placement

To: <>
Subject: [AMPS] Hold on - SWR meter placement
From: (Phil T. (VA3UX))
Date: Tue, 05 Oct 1999 22:05:19
Hold on a minute gents.  I've been waiting for this to slow down a bit
before commenting on one item only.

Jon has said that SWR is constant regardless of line length or position of
the SWR meter (witness the Smith Chart - it says so ).  Absolutely right.

Rich says but...the SWR reading DOES change if I move the meter ahead or
back in the line, in the real world.  Also absolutely right. The SMith
Chart says this shouldn't happen, but it does anyway.

Real world experience and theory don't quite seem to match.  But the
explanation of this contradition - with proper data - is covered quite well
in Walt Maxwell's book "Reflections", and to some extent in Byron Goodman's
classic QST article, "My Feedline Tunes My Antenna".

I ran tests on my own station back in 1990 as a result of Maxwell's book,
and by gum, he's right.  Before I made the changes, the SWR reading in the
shack would change if added or took away a 6 ft length of coax, and the R-X
readings on my GR-916A RF impedance bridge would change also (as expected).
 After the changes, the SWR reading remained constant when I added or took
away the extra piece of coax.  The R-X readings continued to change also,
but they were different than the "before" changes.

I'm not going to do a book review here.  You can read the referenced
material yourselves.

Please continue....


At 09:07 AM 10/5/99 -0700, you wrote:
>>measures wrote:
>>>?  Let me see if I have this straight.  You agree that the 50-ohm SWR 
>>>meter will read 1:1 at the ends of the 1/2 wavelength section, and that  
>>>it will read 1.86:1 at the 1/4 wavelength point?
>>YES!!!! ARRGH!
>>Do you just reply to posts and not read them?
>>Come on, Rich.  Read a little more carefully.
>?  I'm trying, I'm trying.  .  I thought I recalled reading that you 
>supported the theory that the placement of the SWR meter would make no 
>difference in the SWR reading.   I was wrong.  Sorry, Jon.  
>-  Rich..., 805.386.3734,  
>FAQ on WWW:     
>Administrative requests:

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>