Howdy from Texas!
Well FYBO has come and gone and I have almost recovered. I recieved some
e-mail requests for info on the antennas I was using and thought I would
share the following with all. In addition to the double size G5RV
(204ft) that I used on 80m, I had a monoband 8JK on both 20m and 40m.
Here is the scoop......
W8JK ARRAY:
Feed is connected halfway between dipoles with twinlead or balun and
coax.
For optimum performance, the array should be erected horizontally a
minimum
of 1/2 wavelength above ground.When fed in the center, the array
produces a bi-directional pattern. The array may be made directional by
attaching the feed to one of the dipoles.The pattern will be directed
towards the 'other' dipole. Connecting a string the length of 'B'
between the ends of the dipoles will help keep the spaceing of the wires
uniform. Computer modeling of these antennas at the 50 ft I had them
erected at showed 6.3db gain on 40m and 9.6db on 20m.
The idea to use these antennas came from a local ham, W5SB-Bill. He uses
stacked versions of this antenna with great results. He frequently opens
his
shack to operators for many of the contests and his station never fails
to
perform well.
Here is a rough diagram and the calculated measurements I used:
_________________________ ________________________
A | | A
| |
| | <--450 ohm ladder line
| | length 'B'
| |
| |
\ /
X <--- HALF TWIST (180 DEG )
/ \
| |
| |
| |
| |
| |
_________________________| |________________________
A A
20M A=29.4FT B=8.46FT
40m A=58.7FT B=16.9FT
80M A=134.9FT B=38.9FT
'B' Is an electrical 1/8 wavelength with a 1/2 twist between dipoles.
I used random lengths of 450 ohm line to feed these antennas and had
very
good results with them. They are carefully rolled up and awaiting QTTF!
CU---OJ---K1OJ
HOUSTON,TX
QRP-L #732
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