About five years ago I built the short vertical array designed by Tom, W8JI.
I believe this was the first time the design had been built. Tom, as
always, was very helpful in getting the array optimized. I believe that
same design has become used by DX Engineering. I used 20' vertical elements
with 100' spacing (141' diagonal). I used 6 each 60' radials on each
element. This is probably getting close to the minimum number of radials
required for the ground at my QTH. I did not see significant impedance
shifts between wet and dry earth conditions over a two year period the array
was in use. With the short spacing of the array I did find it was very(!)
critical to maintain current balance between each element to maintain
optimum F/B. Each element had to not only have the same impedance (within 2
or 3 ohms) but also had to be resonant within a few KHz of the same
frequency. F/B quickly degraded if element resonance got very far off but
particularly if element impedance got very far off. Your antenna analyzer
will quickly tell the story. Don't forget to take the measurements at the
phasing box end of the quarter wave feedlines.
73...Dave
W0FLS
Hello Nodir and all,
I am also looking at the four square.... my question is about the ground
system.
Ian, G3ROO
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|