Posted by
k6dgw on
Oct 03, 2006; 10:23pm
URL: http://elecraft.85.s1.nabble.com/135-ft-flat-top-antennas-again-ad-infinitum-tp394317p394324.html
George N4YM wrote:
> I use a 130 ft inverted vee, fed with about 55 ft of 450 ohm ladder line.
> The apex of the vee is about 65 ft up. The ladder line stops at the
> eave of my house, just outside the shack, where I use a 4:1 balun.
> From the balun to the homebrew tuner, I use a 7 or 8 ft
> piece of RG 213.
I knew I should have patented this antenna! ;-) Mine is 135 ft (42.148
meters) on each leg with a central angle of about 120 deg opening east.
The ends are a little over head height. The apex is at 70 ft (21.366
meters) right below the tri-bander. I used EZNEC4+ to model the feed
impedance, and then TLW (ARRL Antenna Book, 20th Ed, and also available
on the ARRL Web site) to calculate a compromise length of 450 ohm ladder
line (turned out to be 61 ft) where I put a DX Engineering 10 KW 4:1
balun. Coax to the shack is about 120 ft (36.576 meters) of RG-214. I
use a tuner in the shack to put 50 ohms on the Tx, but actually the SWR
isn't all that bad. The KAT2 and KAT100 match it easily
It is a fairly efficient cloud warmer on 160, although I've worked JA,
HL, and one VK on it. It's gangbusters to the east about as far as
Omaha, and then starts to peter out, although I have worked the East
Coast a few times with 100W. It seems to excel on 80 and has a much
lower radiation angle. It's pretty directive on 40, and works great
E-W, but not too cool into WA, OR, and VE6/7. Oddly, when the path is
open, VY1 is very strong on it as are KL7's. It works great on 30 and
sort of OK on 20. Above 20, the pattern gets really goofy with lobes
squirting RF all over the place ... not always where I would like it.
YMMV, but you never know until you try
Fred K6DGW
Auburn CA CM98lw
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