[Top] [All Lists]

[TowerTalk] Using Screwdriver Antenna as a Base Antenna

To: <>
Subject: [TowerTalk] Using Screwdriver Antenna as a Base Antenna
From: (Pete Smith)
Date: Sun Jun 22 11:58:50 2003
At 10:15 AM 6/22/03 -0400, Chuck Counselman wrote:
>At 1:50 PM -0700 6/21/03, K wrote:
>>...been thinking about mounting another Screwdriver
>>antenna on top of my 10x20 foot and 9 ft high metal
>>top garage in the middle.  I was wondering how well it
>>might work 80-10m without any other radials?
>1. Make a short, fat, low-inductance connection between the shield of the 
>coaxial feedline and the metal of the garage roof at the feedpoint of the 
>antenna.  (Otherwise too much current will flow on the outside of your 
>coax.  This happens in automobile/van/truck installations, too.)
>2. Bond, electrically, well, all the seams of the metal of the garage 
>roof.  (Otherwise, nonlinear conduction will generate harmonics and 
>intermod products.)
>3. Mainly for 80 m, and if your soil conductivity is good, maybe drop some 
>fat conductors from the corners or edges of the roof to 8-ft. ground rods.
>If you do #1 and #2, it should work very well.

As an alternative to the bonding process, I laid 3 125-foot radials right 
on the galvanized 30 x 40 foot garage roof under my Butternut HF9V.  I'm 
not sure whether this is theoretically enough coupling to bring the whole 
roof into play as a counterpoise, or to avoid harmonic and intermod 
generation, though I have not experienced any additional level of either 
one.  But I've used the antenna on my second radio in a number of contests 
and it seems to work surprisingly well with 100 watts.

73, Pete N4ZR
The World HF Contest Station Database was updated 17 June 03.
Are you current?

<Prev in Thread] Current Thread [Next in Thread>