Moving the center of a 75/80 dipole from 65 feet to 75 feet is highly
unlikely to change anything discernibly except the feed impedance of
the dipole, and that not much.
Are you thinking that 75 feet is close to a half wave on 80? A half
wave for calculating heights and such (not the length of a dipole) at
3.5 MHz is around 140 feet.
Get a modeling program. Play around with a dipole, move it up, down,
tilt it, droop the ends, whatever. Once you get the hang of it a bit,
you will realize you have been groping in the dark all along.
Eznec 3 costs less than taking four out to a nice restaurant. If you
are into diddling with antennas and trying to see what if xxxxx, it
will be the most enjoyable piece of software you ever bought.
73, Guy.
----- Original Message -----
From: "Jerry Kincade" <w5kp@swbell.net>
To: <towertalk@contesting.com>
Sent: Thursday, May 30, 2002 12:57 PM
Subject: [Towertalk] Dipole height
> Antenna mavens: In addition to a large 10-el F12 tribander, I'm
running a
> 121' dipole/balun with it's apex at 65' on a 6' insulated standoff,
with
> both ends at about 50'. Sort of a gently inverted V. It works very
well on
> everthing between 10 and 80, and absolutely great on several bands.
The
> question: If I was willing to sweat a little I could the apex up
to 75',
> with the ends at about 55'. Is the extra 10' worth a trip up the
tower, db
> wise, on 75 and 80? My thinking was it might work even better if the
> *average* height were up about a half wave on 80, instead of just
the apex.
> All guys are Phillystran, which is probably one reason it works so
well now.
> Thanks for your opinions.
> 73, Jerry W5KP
>
>
>
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