Re: NEC-LIST: J-pole modeling, also LPVAs

Here is how i modeled a j-pole for 2. I used 6 wires each 1/2 inch in
diameter. 4 wires form a rectangle at the bottom of the jpole. the
vertical sides of the rectangle are 1.5 inches long. The horizontal
sides of the rectangle are 2.5 inches long. extending up from the
upper left corner of this rectangle is a wire 56.5 inches long.
extending up from the upper right corner of this rectangle is a wire
17.5 inches long. The antenna is fed in the center of the wire
forming the top of the rectangle. When I actually built the antenna I
made if of 1/2 inch copper tubing. I made the top (fed) pipe section
moveable so that it could slide up and down a little way. I did this
by using a 1/2 inch copper "T" which i cut open the whole length of
the long side of the "T". By spreading out that side of the "T"
slightly I could make it slide up and down over the pipe.

   I originally had planned just to run the outside of the coax to one
of the vertical members of the jpole and the inside to the other about
1 1/2 inches up. I found by modeling that things worked better if I
actualy made the cross piece of 1/2 inch copper pipe. When I made the
antenna I cut this cross piece in the middle and fed the antenna at
the cut.

  Antenna works great and SWR is almost as modelled!!

  If you don't understand this explanation, let me know your address and I will
send you a drawing. Dave
Received on Tue Jan 06 1998 - 09:36:36 EST