"Jerry Stuckle" wrote in message ...

On 12/19/2014 2:33 AM, Jeff wrote:
By changing
the length of the coax you can make the antenna appear as being resonant
or non resonant, even though the antenna may or may not be a perfect 50
ohm load.

Incorrect, changing the length of the feeder will not change the SWR
beyond any extra loss in the cable. It will change the phase of the
mismatch that is all; (rotate around a constant VSWR circle on a Smith
Chart).

Jeff


# Incorrect. The basic VSWR meter measures the voltage, not the power.
# And if the SWR is other than 1:1, this voltage will change depending on
# the distance to the mismatch.

But isn't it still Vmax over Vmin, regardless of where that happens on the
feedline?


# Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms).
# But a shorted 1/4 wavelength coax shows an open (infinite impedance).
# Somewhere in between (I'm not going to bother to figure out exactly
# where because it's not that important) it will show an effective 50 ohm
# impedance.

# Coax length is unimportant when you have a 1:1 SWR, but if you don't,
# the coax will act as a matching network. And length will affect the
# overall system.

I always understood the VSWR to be constant with the feedline length moving
the parameters around the Smith chart constant VSWR circle.

Thus it is possible by changing length to provide an antenna tuner with R
and X values that the tuner can handle better.