[TowerTalk] DRIVEN VERSUS PARASITIC 160 antenna

[Jim Lux]

At 11:22 AM 1/3/2006, Tim Duffy K3LR wrote:
>Hi Mike!
>
>I think both systems would give you outstanding results!
>
>My current 160 antenna has lots of radials (120 per element (5) that are 1/4
>wavelength (137 feet) long = 75,000 feet of wire (radial wires intersect with
>buss wires and strap to conserve wire)). GROUND mounted radials under all
>elements are very important for this antenna to work. As mentioned in the 
>ON4UN
>book, it has great F/B (32 dB at its peak) and has as much gain as a 
>traditional
>full size 4 square array. It is easy to match and assemble, however the 
>useable
>F/B is limited to about 50 KHz (a good 4 square would have more F/B 
>bandwidth).
>The parasitic system requires less real estate than a 4 square.

An interesting tradeoff appears here.  Bandwidth vs directivity.  If you 
allow adjustable matching & phasing elements (or adjustable elements) you 
can get both really good F/B AND operating bandwidth.  It's the same as the 
"steppIR vs fixed beam" discussion.

There's a lot to be said for a system where it's install and forget.  You 
do all the hard work during install, and then, just sit back and 
operate.  Of course, a computer controlled system could do the same.

Jim, W6RMK