[Elecraft] SWR Readings:Differences

[Jeffrey Otterson]

Unless your antenna is exactly the same impedance as your feedline at the
desired frequency (pretty unlikely)  then the feedline is going to
transform the antenna impedance based on distance from the antenna.  The
exception to this is feedline lengths that are perfect multiples of a half
wave, electrically (that is to say, accounting for the velocity factor)

Any other length will result in a transformed impedance, and corresponding
different VSWR.

You can demonstrate this by changing the feedline length and watching the
VSWR change.  Try adding some small fraction of a electrical wavelength of
coax at 40M and see what your meter shows.  You might be surprised.

TLDR; try adjusting the length of your coax and see if the readings change.

Jeff n1kdo




> Good Evening,
> This is Mark Griffin, KB3Z and I have some questions regarding the SWR
> readings I get at my tower versus what I get on my K3. I will give the SWR
> readings that I got at my tower for a 40 meter rotatable dipole at 55 feet.


>