It seems the same misconception has appeared on two reflectors simultaneously,
the TT reflector and this one! That being that adding a length of transmission
line somehow affects the SWR on the line.
The addition of lossless transmission line changes the complex impedance, but
not the SWR. A perfect SWR meter would not show any difference with the
addition of a length of lossless transmission line. A vector impedance meter of
course would see a difference. For example, as transmission line is added, a
Smith chart would show the different points along the line as a circle, having
different real and complex impedances, but having a consistent SWR.
So what you are seeing is changes in the reported SWR with the internal meters
you have due to impedance changes. This can be for one of two (or more) reasons:
1. There is RF on the outside of the coax. Try adding several beads on the coax
and see if this makes things calm down, and gets identical readings with and
without the jumper. Many SWR meters can be affected by RF on the outside of the
line.
2. The meters are sensitive to the load impedance, and are not 'perfect' or
'ideal' SWR meters. The internal SWR detection in HF rigs are usually pretty
bad in this respect. Perhaps try a Bird meter to see what is really going on.
Another approach is to use a half-wavelength of line. This will make the actual
input impedance at the amp repeat itself at the rig.
-Tony, K1KP
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