[TowerTalk] Shunt feed ??

[K4SAV]

Hmm.. This is hard since you didn't say if you have any other supports 
or room for wires.

First, feeding the tower is going to be hard without insulating the 
guys. If you add vertical wire antennas close to the tower there is 
going to be coupling to the tower, and since the tower has multiple 
connections to earth (no radials) there is going to be some loss.  But 
an antenna with a little loss is a lot better than no antenna at all.

An inverted L, mentioned by K1TTT, would be good for 160 if you have a 
support for the top part, and room for radials.  Try to keep the end of 
the L as high as possible.  The more it droops, the lower the radiation 
resistance of the antenna, but with 90 feet to work with, it shouldn't 
be too bad.

You could also use the tower to support a vertical for 80, but again you 
need radials. I would expect the tower to act as a reflector, so put it 
facing your favorite direction.

You could hang a sloping dipole for 80 from the top of the tower, 
keeping the end at least 10 ft off the ground.  I would expect some 
reflection from the tower with maximum gain in the direction of the 
sloping wire.  This antenna should have a lot of vertical component so 
it should produce some low angle signals. There will be some ground 
loss, but the extra gain may make up for the loss. This might produce a 
cardioid pattern covering 180 degrees. Do you have room for two, another 
for the other 180 degrees?

You could use a half sloper for 160 from the top of the tower. This will 
probably have a little more loss than an antenna insulated from the 
tower, but it shouldn't be too bad, and it should produce some low angle 
signals.  My guess is that is is not going to be very directional.

An inverted vee for 80 should work but it isn't going to produce low 
angle signals.

Jerry, K4SAV


Dan H. Gaylord wrote:

>Gentlemen -  In my younger days, when dollars were spend on three growing kids and hamming was a low priority budget item... I planted a 92' Rohn 25 tower, guyed 90 degrees around  at three levels.  My 50x400 foot lot would not support the recommended guying pattern (one set every 120 degrees) and keep the beam that I wanted to put up over my own lot/house.
>   Taking the cheap route, I did not insulate the guys.  
>   Dows anyone have a trick to pulling a rabbit out otf the hat & a way to get me a good low angle on 160, even 80????? Short of re-guying the whole thing (lottsa bucks) and insulating it now,  I'm outta ideas...
>73, Dan W7IDG 
>_______________________________________________
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>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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