Tom,
Here is a probable fix for 40m.
If you have any of the commercial 450 ohm ladderline, use it and add 13 ft.
of line to the antenna.
I assume you can run it inside your shack, which is why I say to use
commercial stuff (easier to work with and zigzag back and forth than the
home made stuff).
If you don't have commercial ladderline, then add about 15 (or 14 ft.) of
your homebrew openwire to the feedline.
The trick is to add an electrical 1/8 wavelength.
I don't know the velocity factor of your home brew line, that's why I can't
say the exact length but it will be about 14 or 15 ft, maybe even 16 ft.
I'm pretty sure that will fix 40m, and probably 30m as well.
MOST LIKELY, THE ONLY PROBLEM YOU ARE HAVING IS THAT YOU HAPPENED TO HIT A
VERY UNPRACTIVAL TOTAL LENGTH OF ANTENNA PLUS FEEDLINE!
I use the same antenna with the same matchbox (I have the MFJ-974B) and it
produces a very good match on ALL bands, from 80 thru 10, but I have a
longer feedline, whose length I have not measured. It runs exactly from the
antenna to the shack, and I got lucky!
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of tom stewart
Sent: Sunday, February 13, 2011 7:17 PM
To: TenTec@contesting.com
Subject: [TenTec] Antenna follow up- asked for help in January- need more
help.....
OK,
Many came to my aid when I asked for suggestions. I made some choices and
built an antenna. I tried hard to maintain spacing and avoid metal by at
least a foot. It did not come out well so I need help. Here are the details
if anyone has some suggestions I would be grateful-again.
1. Purchase "Ladder Snap" spreaders to build 600 ohm feeder.
2. Purchased plenty of 14 gauge THHN wire.
3. Because of room constraints, the legs of my inverted Vee are 31 feet.
Center is 35 feet high and the legs end at about twenty feet.
4. Legs to feeder is continuous- feeder is 45 feet from center and
terminated by grounded shield coax through window pane(vinyl).
5. Tuner is for now an MFJ balanced- model 974-I think.
6. reactance is high on all bands. It will only tune up on 14MHZ. tuner
arcs if I persist at 7mhz
7. readings with antenna analyzer are as follows:
Readings are at the bottom of the bands beacause I operate CW only.
7.020mhz r57 x158 swr 10.0
10.110mhz r168 x 135 swr 6.0
14.020 r21 x58 swr 7.5
18.075 r20 x70 swr9.1
Thanks in advance- I know it is difficult to say with this limited
information but I am at my wits end- about 10 hours into this
Tom N7ESE
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|