I have a shunt fed tower which is 70 feet tall. It is 45G and has a 6L 20 on
top with a 65 foot boom. It also has a 5L 15M yagi with something like a 34
foot boom on the side at about 35 feet.
For the purpose of modeling the antenna with a reflector 100 feet behind it, I
just put the DE in as a 18 inch diameter, 124 foot tall vertical. The actual
reflector I have up is a T shaped element that is 100 feet vertical and 36 feet
on top (18 feet either side of the center of the vertical part. This element
is #18 copperweld. I have it shown over Real/Mininec ground and it shows 5.37
dBi at 1.825. The driven element and reflector have a decent ground system
tied together in the center with a bus wire - something like 100 radials under
each.
Am I missing something in the way I am modeling it or should I expect to see
the results shown by the computer. I am suspicious of the model since I can
change the vertical portion of the reflector to #10 wire instead of #18 wire
and the max gain moves up about 50 khz. I would have thought it would have
moved it down some?
I put the reflector back up over the weekend and am going to re-do the shunt
feed on the tower but wanted to make that reflector element whatever length
should be best first.
If anyone out there knows how to model this thing properly, I would appreciate
some help.
Thanks...Stan, K5GO
_______________________________________________
160 meters is a serious band, it should be treated with respect. - TF4M
|