Topband: Tee Verticals

[Jim Brown]

On Thu, 19 Oct 2006 12:25:30 -0400, Bill Gaines AD8P wrote:

>For several years now I have used a 65' tall "Tee" vertical on 160. 
>It is an open wire fed 80 meter dipole with the feed point shorted 
>and fed together. This is fed against  6 or 7 elevated 1/4 wave 
radials.

Several thoughts. What I'm using is quite close to yours -- an 80/40 
dipole fed with about 70 ft of 72 ohm kW twinlead (long out of 
production) against 25 radials that are 70 ft long. I think it's 
optimum on 80 (and works like it is), but could use some more height on 
160. 

So my next move will probably be a dedicated top-loaded vertical (I'll 
move the dipole to different trees) for 160, but in the form of a fan 
dipole using spacers. I think I can probably rig the top of the Tee to 
about 100 ft between two trees, so one wire will be part of the Tee. 
The other wire will be a quarter wave on 80, and I'll hook both of them 
in parallel at the base. I'll probably use spacers that put the two 
wires about a foot apart. I'm hoping to pick up a dB or two from the 
longer radiator on 160. (Any predictions on that?) 

Second thought. Elevated radials need to be a signficant fraction of a 
wavelength above ground to provide the full benefit of elevating them. 
See the ARRL Antenna Book and ON4UN's book for a discussion of this. So 
the second thing I would do if I were you is to look seriously at your 
radial system. You might find a few dB of improvement there. I've 
bought some junk wire to improve my radial system, and expect to pick 
up a dB or so by the time I'm done. 

The combination of radials and taller vertical radiator has the 
potential to give me something like 3 dB, which is equivalent to 
doubling my transmitter power. 

73,

Jim Brown K9YC