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November 30th 05, 11:51 PM posted to rec.radio.amateur.antenna

In article ,
(David B. Thomas) wrote:

"ml" == ml writes:

ml i was trying to figure loosly in real world case what the
ml difference would be (generally speaking) between say a
ml verticle all band commercial antenna on my roof (of my tall
ml apt building) i'd naturally install it's radial kit

ml vs

ml a equal all band (yeah i know it'd be tall) virticle dipole
ml (tweeked w/a tuner sgc at feedpoint

The commercial vertical probably uses traps or other means to act like
a quarter wave ground plane on all bands. This would be roughly
equivalent, performance-wise, to a separate vertical dipole cut for
each band.

The issue with using the tuner is that a tall dipole used on a high
frequency will throw a lot of energy up at high angles. On 15 and 10
meters, you'd probably rather have a nice low angle pattern. Then
again, when those bands are open, you can usually afford to have an
inefficient antenna as propagation tends to be excellent.

So, if you're looking to put up something fast and cheap, the dipole
and tuner idea can certainly work. If you do that, try to keep the
feed line perpendicular as long as you can before it drops down.

David
N5IZU

thank you very much david for your help, i was sorta thinking a
commercial one might radiate out more that way and was double checking
to see what i might have missed

appreciate the advice

tnx