That's probably because none of us have a true idea just where our
effective "ground" is. It's not like there is some high conductivity
zone in the top few inches of soil, or that everyone's soil conductivity
profile is at all similar. I'd bet that in some low conductivity soils
the effective ground is several meters below the surface, and I'll also
bet that it is at least to some extent dependent upon the frequency of
interest. I use and depend upon EZNEC and HFTA all the time, but I
don't pretend they are any more accurate than the data I feed them.
Dave AB7E
On 9/4/2013 6:37 PM, Bob K6UJ wrote:
FWIW I have never had good results trying to calculate the difference in
resonant freq from low heights vs the desired height on an inverted V.
I finally reached the conclusion it was a waste of time to try and calculate
the difference.
Hoist the center up to its final height and leave a generous amount on the ends
and lower and raise each of the ends and keep pruning till you get nirvana.
Bob
K6UJ
Onp 4, 2013, at 5:42 PM, Wes Attaway (N5WA) wrote:
Why not use EZNEC or similar program to model the dipole at 8' straight
across and then at the 65'apex with whatever the height of the ends are?
This should give you a good idea of what to expect.
You should be able to determine how to cut the dipole while it is at 8' so
that it will be close to what you want when you raise the apex.
----------------- Wes Attaway (N5WA) -------------------
1138 Waters Edge Circle, Shreveport, LA 71106
318-797-4972 (Office) - 318-393-3289 (Cell)
Computer Consulting and Forensics
-------------- EnCase Certified Examiner ---------------
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
john@kk9a.com
Sent: Wednesday, September 04, 2013 7:35 PM
To: TOWERTALK@contesting.com
Subject: Re: [TowerTalk] Cutting a dipole
The resonant frequency and the impedance will go up if it remained a
straight dipole. Tuning it at 8 feet high is a waste of time.
John KK9A
To:<towertalk@contesting.com>
Subject:[TowerTalk] Cutting a dipole
From:"James Setzler" <jms_k1sd@verizon.net>
Date:Wed, 04 Sep 2013 18:32:38 -0400
List-post:<towertalk@contesting.com">mailto:towertalk@contesting.com>
Greetings
I should know this but I've not made too many dipoles.
While it is hanging at 8 feet so I can get to it, I've cut a 40 m dipole to
the frequency I want. When I raise the apex to 65 feet as an inverted V,
how will the resonance frequency change?
73 James K1SD
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