Topband: RoofTop TopBand Antennas - Shunt Fed Towers?

[kd4rwn@bellsouth.net]

Hello All,

	I am about to undertake an antenna upgrade for my club 
station. 1 important element has yet to be figured out: What, if any 
antenna we can have for the top band. Let me describe the 
situation. We are a University Club station.. All of the antennas, 
Towers, Etc. need to be on the roof, In a space about 100 X 75 Ft. 
We currently have 2 towers, Both Rohn 25 at 40 ft each, On 
opposite sides of the roof. Tower #1 Has all the Repeater Antennas 
and Vhf/Uhf Gear.. Tower #2 Is HF and holds the 2 tribanders (Th-6 
at 45, A-4 At 15). The VHF tower has insulated guy wires, The HF 
Tower is not guyed. We currently have a 40/80 Fan Dipole running 
between both towers, With the 40 meter wire running straight 
across to both, the 80 of at a 45 degree angle. (Below is Supposed 
to be a rectangular box btw.. Forgive the artwork...)

		---------------|
		|   X  VHF |     Each Long Side 100 Ft
		|              |          	   		
		|              |   	         
  	|              |   	         
		|              |   	         
		|              |   	         
<---		|              |   	          (Not To Scale)
NE       |              |   	        
EU)     |              |   	         
            |              |	           ^^^ = Entry Structure 
		|              |	  	                        
		|              |        	   	
		|              |              
		|     X HF  |   
		|   ^^^^     |      
		----------------
	Each Short Side 75 Ft


	Now, what antenna can we fit up there? No room for a dipole. 
We tried a sloper but ended up bending it around a few corners and 
was pretty much deaf on receive and transmit, being 1 ft off the 
ground for alot of its run. An inverted L would be next to impossible 
to set up, Let alone in a useful direction, Considering the wires 
already running around up there.. So that leaves me with 1 thought, 
Unless someone can help out with a another suggestion: Shunt 
Feeding the Towers.

	Now i know they are both a bit short, But with the 2 Beams on 
the HF tower, Im thinking it might work. But there is no real 
ground per say up there.. The only ground is the piece of 
grounding braid, Thats attached to the tower; Part of the roofs 
lightning protection. Runs around the roof, To drop points, Where 
the braid runs 50 ft down to the ground, then to rods that go down 
another 50 ft. 

	My question is, Is there hope of shunt feeding the towers? I am 
ewbie when it comes to top band antennas, so any and all help 
will be appreciated. Any websites and such on the subject matter 
would be helpful.. Thanks in advance for the help.Much appreciated 
by this station...

Ulysses Rodriguez - KD4RWN
President - University Of Central Florida ARC (K4UCF)
Member: ARRL, FCG, WWYC # 77
kd4rwn@arrl.net



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