At 2:15 PM -0700 6/21/03, Jim Lux wrote:
>It will work better than it does on your car, but not as well as, say, a
>dipole. It is, after all, physically short, with a loading coil. The
>loading coil does have some loss.... It's physically short, so the
>radiation resistance is quite low....
Jim's comments are valid, and important. I regret that I did not
qualify my reply to your question by making the same points.
A short, low, vertical antenna will never work as well as a
horizontal dipole at a reasonable height, or even as low as the top
of the vertical antenna.
Loading-coil loss will be a problem on the lowest-freq. bands. A
very big problem on 80 m and a big problem on 40 m, but not bad on 20
m and higher. The Q of a screwdriver antenna coil is sub-optimal.
(A short fat coil would have much higher Q.)
Loss in your impedance-matching network or transformer will also be a
problem on the lowest-freq. bands. Again, a _very_ big problem on 80
m and a big problem on 40 m, but not bad on 20 m and higher.
All of the above applies to vehicle-mounted antennas, too -- not just
to your proposed garage-roof-mounted antenna. All else equal, your
proposed garage-roof mounting will work better than vehicle-mounting.
-Chuck, W1HIS
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