Hi, folks.
As promised, I had some time this evening to use my new TW1 to take some
systematic SWR readings on my re-constructed Windom antenna.
To give you the short story, my original windom was a coax-fed 80-meter
Windom. It was fed by RG8U coax, and had a 4-1 balun at the feed point on
my tower. The feedpoint and legs were all about 35 feet off the ground.
The short leg was 44 feet long, and the longer leg was 80 feet long--which
turned out to be way too short.
Last Sunday, I had a friend come over, and we added 9 more feet to the long
leg, based on re-calculating our formula for an off-center fed 80-meter
windom. Our new calculations suggested that the proper length for the
entire antenna should be 132 feet--44 feet on the short end, and 88 feet on
the long end. The antenna heights are the same as before, and the new
8-foot extension on the longer leg is hanging down vertically, since I had
no room to extend it horizontally.
My SWR's are considerably better than they were before, but they still don't
seem great. Let me give you some readings to show you what I mean:
I took readings at the low end, the center, and the high end, of the
following bands, and came up with the following SWR readings:
80 meters:
2.9 2.1 1.1
40 meters:
3.3 3.1 2.3
20 meters:
3.0 2.4 1.7
15 meters:
3.8 3.9 4.8
10 meters from 28.05 to 28.5(very surprising):
5.1 4.7 3.4
17 meters:
1.7 1.8 2.0
30 meters:
around 8.1 to 1 throughout--basically untunable.
I guess what surprised me the most was that the antenna was lengthened an
entire 8 feet on the long end, and still seems to resonate toward the top of
75 meters, and I thought My SWR's would be better all around on 40, 20, 15,
and 10 meters.
The great SWR's on 17 meters also surprised me.
I didn't expect the antenna to tune well on 30 meters, which is no problem
since I never use that band anyway.
Can anyone tell me what might be going on here? Does anyone have
suggestions for modifications that might improve things?
I think the antenna is clearly usable for this week-end's PA qso party,
since the TS480 auto-tuner should tune it with no problem on 40 and 80, but
I'm interested in trying to make things better all around.
Thanks for any help you can give.
73 from Tom Behler: KB8TYJ
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