[Antennas] 2 trees 150' apart 60' high

[A10382]

Hi Jerry,

And right you are.

I've always cut a wire antenna about 2% longer and then trimmed it for
best operation after it's up - usually on the center freq most important
to me.

I've generally found a 1/2 wl dipole, below 30MHZ, will have a rather
narrow natural bandwidth of decent SWR.. maybe 150-350 KHZ.  In some
bands, that's the entire band.  In some others, it only covers a small
part of the entire band.  This makes the use of a tuner very beneficial
if you're going to use a few parts of a relatively wide band - like 80,
15, or 10M.

There are wire antenna designs with larger bandwidths - like the folded
dipole, bazooka designs, large diameter radiators, or multi-wire ones,
but that bandwidth sometimes comes at the expense of some radiation
efficiency.

Antenna design is as much art as science.  One person's perfect antenna
is the next person's air cooled dummy load.  With all the science, laws
of physics, legend and lore (some of it inaccurate), and individual
operator's experiences, talking about a subject like this can make for
some verrrry lively discussions.

Want the e-sparks to fly ?  Just ask a question about how to achieve the
'best' SWR, or the preference of open feedline over coax feed.
Lightening protection and grounding questions can also makes the e-rocks
start a-tossin'.

The archives of this list have some very good dissertations and on-line
reference links from some very knowledgeable and experienced hams.  Not
being an rf engineer, I defer to them that's smarter than me.
====




 ._._.


----- Original Message -----
From: "Jerry Forwood" <e.j.forwood at juno.com>
To: <223bthp at cox.net>
Cc: <Antennas at mailman.qth.net>
Sent: Thursday, June 02, 2005 5:05 PM
Subject: RE: [Antennas] 2 trees 150' apart 60' high



The last time I looked the formula for a 1/2 wl dipole was 468/Feq in
MHz.  468/3.75 = 124.8 ft.




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