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
|