Bob,
You should lengthen the two top loading wires so that the basic resonance
of the vertical is about 1.9mhz. Then add a Hairpin coil across the feed
point and adjust it/ top loading to place the minimum SWR where you want it
in the bottom of the band e.g. 1825khz. This works well and also gives you a
DC grounded vertical.
73 Clive GM3POI
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Chortek,
Robert L.
Sent: 17 March 2019 22:02
To: topband@contesting.com
Subject: Topband: Top Loading Advice
Fellow Topbanders,
I just finished replacing my damaged base loaded vertical and have a
question about the optimum amount of top loading.
A bit of background - my new vertical is a 55' #12 wire supported by a 60'
Spiderbeam fiberglass pole. At the top there are 2 -41' top loading wires
running roughly at 180 degrees from each other, angling down at about 45
degrees. The ends are at about 25' . Since the resonant point is about 2
MHZ, I am still using an air core base loading coil 6" in diameter made of
No. 8 solid copper wire to bring it to resonance at 1825 MHZ.
I could lengthen the top loading wires somewhere between 4 - 10' each (and
reduce the amount of base loading needed), but it will bring the ends to
within about 15' and 20' of the ground.
My question is this: At what point will lengthening the top loading wires
and bringing the ends closer to ground offset the improvement gained by
reducing the amount of base loading?
As it is, the antenna is a HUGE improvement over my base loaded vertical (on
the order of 6-9 db from stations in the RBN within the ground wave).
Should I leave it alone and be satisfied with the improvement or lengthen
the top loading wires. If so, by how much?
Thanks in advance from any advice.
73,
Bob/AA6VB
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