I wonder if the amount of coax added here were really coax stubs. The old
method of matching a line was to add an open or shorted coax stub at the 50
ohm point and have the stub exactly cancel the reactance at that point
producing a perfect match from the stub back to the transmitter. This was a
classic problem to solve back in "Fields and Waves" for me in 1966. We used
smith charts and slide rules back then to solve the problem.
Carl Moreschi N4PY
Franklinton, NC
----- Original Message -----
From: <AC5E@aol.com>
To: <tentec@contesting.com>
Sent: Wednesday, January 29, 2003 9:22 PM
Subject: [TenTec] Jupiter SWR, and VSWR generally
> This question has come up many times and always reminds me of my old
> professor deponing "If you don't like the VSWR, change the length of the
> transmission line."
>
> Essentially, the indicated SWR changes with feedline length. Within
reason,
> some length of transmission line will provide an INDICATED match to the
> transmission line regardless of how mismatched the transmission line to
load
> match may be.
>
> Back in the days when George and I were young, one of the most popular
home
> brew accessories was a box with short lengths of RG8 and toggle switches.
>
> If you couldn't get the antenna to match straight through, you could
switch
> in 1, 2, 4, 8, 16, and 32 foot chunks of cable, stretching your coax 1, 2,
3,
> 4, 5, 6, 7, 8 feet, etc.. Some combination would provide a good match to
your
> transmitter.
>
> And that being the case, it's no surprise that the SWR in a transmitter
and
> the SWR in an outboard meter are different; unless the actual SWR at the
load
> is really 1:1. The only surprise would be if the meters read the same.
>
> 73 Pete Allen AC5E
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