[Amps] Trimming the transmission line

[Gary Smith]

Thanks for the VERY good explanation on this issue.
73's,
Gary...wa6fgi


----- Original Message ----- 
From: "Peter Chadwick" <g3rzp at g3rzp.wanadoo.co.uk>
To: <amps at contesting.com>
Sent: Thursday, October 11, 2007 9:05 PM
Subject: Re: [Amps] Trimming the transmission line


> The 30S1 is a bit of a special case, since it relies on the length of line 
> because of phase changes. Because there's a change in input impedance with 
> power level, if the length of line isn't an exact multiple of 90 degrees, 
> the input reactance changes faster than the change in the real part of the 
> impedance, and thus you get phase distortion.  Pappenfus states, regarding 
> the 30S1, 'Other transmission line lengths can be used if the attendant 
> increase in distortion is acceptable'. If you use a 30S1 with a modern 
> solid state transceiver, a differnt length is going to be needed, since 
> the length of line for the 30S1 is designed to go with the various Collins 
> tube rigs of that era.. And I suspect the input SWR may not good enough 
> for a modern solid state rig. It is perhaps arguable that all amplifiers 
> should have a special length of line, but whether or not the phase 
> distortion introduced is of such level as to be worth worrying about is 
> another matter.
> There are other places where line length matters, such as phasing lines 
> for vertical arrays, but they aren't trimmed for SWR!
> 73
> Peter G3RZP
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