Yesterday I spent an hour or so crawling up and down the tower to load
it on 160M. It seems to work just fine. Here's the story:
I read Jeff K1ZM's book on Top Band DXing and followed his design for
loading my tower. I used 3/4 inch PVC tubing to fashion T's to hold three
drop wires off the tower. The shorter sections of the T's are 9 inch pieces
glued into either side of a PVC T fitting; total width, including fitting
itself, is about 20 inches (2X9 +2). The four long pieces are approximately
the following lengths: 66 inches, 60 inches, 54 inches and 48 inches. I
spray painted them medium gray. I placed these T's into the tower bracing,
beginning with the longest one near the bottom and installing the next
shorter ones at 19 feet, 38 feet and 56 feet (just under the rotator shelf).
The long part of each T is inside the tower, sticking out, and the short
sections are all two feet off the tower face. I used cable ties to hold the
PVC in place on the tower braces.
From the top of the tower I dropped down three #14 THHW insulated
stranded wires. I stripped the ends of each and clamped them with a Harger
213T clamp to the angle brace under the middle rotator plate three feet from
the tower top. On the way down I taped each drop wire to the short
horizontal PVC pieces, one wire in the center and the others about an inch
in from the ends. At the bottom of the tower I stripped each wire and
connected them to a large-ish variable cap. I connected the center of the
coax feed to the other cap terminal and grounded the coax shield.
As my MFJ goes nuts on 160M (nearby BCB station and no MFJ filter yet),
I enlisted my daughter's help in adjusting the cap for minimum SWR (about
300 pF) as shown on my TS-570's SWR meter. Without radials I show a 1.4:1
SWR from 1.8 to 1.9 MHz. I know this will change after I add a few radials.
(The tower does have lightning ground radials and copper ground rods, but
they're a minimum of 18 inches below the surface.) I may also have to move
the top tap point up or down as well to optimize the match.
I worked a few SSB stations on 160 last night, from upper NY state to
the midwest. Most gave me S9+ reports. I was running barefoot 100W.
Likewise, most of the other stations were S9+.
I haven't compared the loaded tower's performance to my inverted L. I
need to rearrange some coax inside the shack to do A/B comparisons, but I'll
let you folks know the results.
Gene Smar AD3F
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