Wow! I am really impressed with the quanity and quality of feedback I got
back from my original question about making a dual band vertical for 80
and 160. This is a great resource of knowledge!!
There were many great ideas - some of which I never considered.
There is a bit of information I left out of my original post. The intent of
this project is to leverage my 80 meter 4 square and use it as a parasitic
array on 160 meters - without a significant impact to the 80 meter operation.
My current gamma matched tower its in the middle of the 4 square. There is
47 feet of spacing from the middle to each element. This is a bit close for
a parasitic array - but it still should work.
You can see it here:
http://maps.live.com/default.aspx?v=2&cp=rk24rs4szn58&style=o&lvl=2&tilt=-90&dir=0&alt=-1000&scene=5591280&encType=1
One thing I realized after seeing some of the suggestions - is that I didn't
have to use a trap to make this work. In fact - there really isn't any need
to even use the 80 meter element at all (from an electrical standpoint) for
the 160 meter element.
My current thinking is to use some PVC tubing coming out of the top of the
vertical (the top of the vertical is 3" irrigation pipe) and then run a
wire up above the active 80 meter vertical and slope the wire away from
vertical - so there is some separation between the wire and 80 meter element.
Maybe I will even put a small horizontal element to hold the wire away from
the vertical at the top. By sloping the wire on the "far side" of the
vertical (away from the driven element) - I can probably even fudge another
10 feet of "boom length" on each end.
I'll see how much higher I can make the vertical - probably around 80 feet,
and then run some top loading wires (one of which can almost be horizontal
going towards the "driven element".
I plan to try one element first and get the dimensions right. I would be
trying to make a director tuned to about 1910 kHz with just the wire and
then use an inductor to bring the resonance down to 1760 kHz for a reflector.
I'm pretty excited about this experiment. I'll keep everyone up to date as
this project proceeds and of course would be interested in any feedback on
this plan.
Tree N6TR
tree@kkn.net
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