kb1gmx wrtoe:
If getting to the end of the cable use a different one for the occasion. I've
done this for many times when testing elevated antennas.
By that I believe Allison means that if you have 78 feet of RG8X from rig to antenna,
you could calibrate your VNA using 78 feet of RG8X coiled up at your feet in the shack.
Being off in length by 1/20'th of a wavelength at the highest frequency of interest is probably ok.
Be wary of one one thing is the cable is an intrinsic part of the antenna such
as in an End Fed testing as the original poster wanted (remote isolated VNA)
you need to simulate the operating configuration. If you literally had a
nanoVNA with Wifi connect at the end of an end fed with out coax shield
connection you would get erroneous data.
Yes, the EFHW needs at least a few feet of counterpoise.
In normal use, the coax from matchbox to the rig is the counterpoise.
When checking out my EFHW-8010 I used a portable antenna analyzer
(the AQRP VIA), had it attached directly to the matchbox coax port.
The SWR looked good while standing on a 7 foot aluminum stepladder
and holding the analyzer, that was enough of a counterpoise for the very
high impedence EFHW. But if I let go of the analyzer and drew
a couple feet away, the SWR was drastically worse.
Jerry, KE7ER
