In a message dated 98-10-16 19:48:31 EDT, n6rfm@gis.net writes:
> Just finished putting together a C4. Can anyone comment on the expected
> VSWR changes for the 40M element as the antenna is raised. At five feet,
the
> EF-140S is low at about 6.65 MHz. I can move the linear loading jumpers way
> out to bring the antenna up to 7.08 MHZ, BUT the jumper locations are out at
> about 35 inches not 14-18 inches as specified. Should I just wait until
it's
> "up the tower" to make the adjustments or raise the antenna to a higher
level
> (10 - 15 feet ?) and try again ?
Start with the factory dimensions. You get big added capacity from the
close proximity to the ground which will make it generally resonate low.
Raising it 10-15 feet still isn't high enough to eliminate ground effects.
I've never worked with a Force 12 linear loaded antenna that was exactly
right when set to the factory dimensions. There are your starting point.
> Am I just too close to the ground to get an accurate measurement ?
Yes.
> Adjusting this element after the antenna is on the mast looks tricky !
It's not. You need a 5/16" nutdriver and an antenna analyzer to get it
done. Measure the feedpoint with the coil installed and you'll be able to get
it dialled in.
Cheers, Steve K7LXC
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