[BC] Problems that make you want to scream!

[DANA PUOPOLO]

You are not changing the VSWR. What you are doing is changing the position of
the voltage peak. 
See, most VSWR detectors read voltage. By adding to (or taking away) line, you
are moving the voltage peak away from the voltage reading detector (think sine
wave here).

The VSWR does not change, only the meter's reading of it.

-D

------ Original Message ------
Received: 
From: Cowboy <curt at spam-o-matic.net>
To: Broadcast Radio Mailing List <broadcast at radiolists.net>
Subject: Re: [BC] Problems that make you want to scream!

On Thursday 13 October 2005 07:01 pm, Bill Croghan wrote:
>A high SWR indication on my Moseley 950 system went away on the Moseley when
>I added a short jumper length of cable to insert the Bird meter in line.
>The bird did not indicate much reflected at all.  It was acting like a
>matching section I guess.  I didn't bather to calculate the correct Matching
>length, but rather just fixed the system.  At 950 MHz it's practically
>witchcraft at times.

 Sounds like the old CB good buddy thing of simple cutting the line to
 make the transmitter happy.
 Works fine below about 50mhz, provided the line loss is low enough,
 but much above that the losses become significant, and any indication
 of a change in VSWR due to a change in line length, by inserting a Bird,
 or much of anything else, suggests that fixing the real problem ( the
 mismatched load ) is a far better approach.
 ( unless, of course, your tuning a multi-cavity filter, in which case the
 designed coupling lines will frequently have very specific lengths, and
 may not be changed without upsetting the whole apple cart )
 Can anyone say "linear transformer" ?

-- 
Cowboy

http://cowboys.homeip.net

My theology, briefly, is that the universe was dictated but not
signed.
		-- Christopher Morley

_______________________________________________
This is the BROADCAST mailing list
To send to the list, email: broadcast at radiolists.net
For sub changes, archives and info on this other lists:
http://www.radiolists.net/