Howdy!
I was recently sent a new loading coil and improved base set for my
prototype St. Louis Vertical antenna. W6MMA has applied some practical
antenna theory and vastly improved on my original twinlead coil.
This handsome custom-made coil tuned coil is inletted into a pvc pipe
form which slips over the second section of the collapsible pole. The
elevated assembly is positioned at eye-level which also helps minimzed
ground induced losses. The turns are shorted with a machined sliding tap
and follower. There is about 50' of tinned wire in the coil. It will
cover 10-80M and can also handle 160M meter with some radiator
enhancements.
A good match is easily achieved and most importantly the matches are
repeatable. This is mandatory for operating portable at multiple
locations. It also means that the tuner can be left at home with this
version of the SLV.
A new base set includes a BNC antenna connection and a radial attachment
point. The pole itself slips into a pvc socket and can be epoxied in
place if desired. This assembly in turn fits into a rugged reinforced
mounting. The ground system has been upgraded to five conductor rotor
cable that can be optimized for four bands of interest. This radial
concept compliments an unbalanced or coax fed antenna.
In search of an impartial second opinion N0OCT was skillfully recruited
for field testing in (almost) 50F weather. "Suns out, we'll be just
fine" turned out to be a bit of a stretch! But, duty called! <g>
In a weather abbreviated effort Jim Smith and I had no problems (other
than frozen earth) installing the modified antenna. Using Jim's Autek RF
Analyst we quickly found a match and started working stations on 40CW.
With its new coil the modified SLV hears remarkably well. So well in
fact that I'm not even going to bother with A-B testing against my
original design. It's that good!!!
One surprise! The cold caused the VFO in my Argo 509 to drift right out
of the passband with some contacts. FYBO aspirants might wish to take
note and take along an extra blanket.......for the rig!
More experiments are in order as soon as the weather improves here in
St. Louis. In the interim W6MMA is due a well deserved "atta-boy" for
taking the SLV concept a big step forward. MNY TNX OM!
Vern Wright is working on some more SLV improvements and I'm sure he'll
get the word out here on the QRP-List when the time is right. You'll
like 'em!
73 de Dave, NF0R nf0r@slacc.com
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