Tom, The issue on optimized reflector and directors for passive vertical
beams, is that the specific need of a certain resonant frequency for the 2
passive elements can be affected by the interaction of the vertical with the
ground and other nearby tress and items. There is really no "formula" that
will for sure work. What you need is to cut each element to a known
resonance of the beam design for each element. And that cut length should
be determined in the expected location of the element. Basically, the
technique I use is to start with 10% higher than expected on ref and dir.
Put up the element, drop the other 2 elements to eliminate their
interaction. Cut for the frequency that the model is implying for that
elements resonant frequency. Repeat with the others. Then raise all of
them up and match for a good SWR.
You are loading up each element to determine the resonance but then only
loading up the DE in real use.
Ed N1UR
Hi All
I have a 40 meter vertical dipole that I would like to put a reflector
behind.
I was looking in a CQ Contest magazine at an article from N6BT of the Team
Vertical group. They put up verticals for their contest setup. One of the
antennas they used was a vertical beam on 40 with DE and Ref.
According to the modeling, he said the regular calculated dimension for the
reflector didn't work. It had to be a different length, but he didn't say
what it was. I can't find anything online about this antenna.
Does anyone know the formula for cutting the reflector length for the
vertical beam? The vertical dipole is in a tree with the bottom about 6
feet in the air.
Thanks and 73
Tom W7WHY
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|