John,
concerning the point "a", source line and load, I was not talking of SWR
changes but of impedance changes between antenna and transmitter, moreover
as a direction and not as a versus.
The best condition to transfer energy is that generator and load have the
same impedance. A 100 Ohm transmitter used to feed the combination of a 50
Ohm line and load, independly by the SWR @ 50 Ohm, will work in a badly
mismatched condition, similarly to a transmitter looking into a load that
causes high SWR.
This consideration has twice sense because in the amateur world the
transmitter antenna is very often also the
receiving one (a source) and creating a symmetrical condition where no
impedance transformations occurs is quite a desiderable condition to
preserve.
Concerning the point "b", the half wave multiples, you're right and I
apologize not to have specified again about the most obvious and known
property of the transmission lines many times threated.
73,
Mauri I4JMY
-----Messaggio Originale-----
Da: John Devoldere (ON4UN) <john.devoldere@village.uunet.be>
A: Maurizio Panicara <i4jmy@iol.it>; Gilmer, Mike <mgilmer@gnlp.com>; 'AMPS'
<amps@contesting.com>
Data invio: mercoledì 29 settembre 1999 0.28
Oggetto: Re: [AMPS] Re: swr
Let me "improve" this a little:
a/ line and load have same impedance (the matching condition at the
"observing end" of the feedline does NOT influence the SWR!)
b/ the line is a half wavelength or multiple of half wavelengths long
73
John, ON4UN
----- Original Message -----
From: Maurizio Panicara <i4jmy@iol.it>
To: Gilmer, Mike <mgilmer@gnlp.com>; 'AMPS' <amps@contesting.com>
Sent: Tuesday, September 28, 1999 20:07
Subject: R: [AMPS] Re: swr
>
> Not considering losses, there are only 2 conditions were no changes in
> impedance occurs between antenna and transmitter :
>
> 1 ) Source, line and load have the same impedance
> 2 ) The line is half wavelenght
>
> 73,
> Mauri I4JMY
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|