[TowerTalk] Cutting a dipole

[David Gilbert]

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 at contesting.com] On Behalf Of
>> john at kk9a.com
>> Sent: Wednesday, September 04, 2013 7:35 PM
>> To: TOWERTALK at 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 at contesting.com>
>> Subject:[TowerTalk] Cutting a dipole
>> From:"James Setzler" <jms_k1sd at verizon.net>
>> Date:Wed, 04 Sep 2013 18:32:38 -0400
>> List-post:<towertalk at contesting.com">mailto:towertalk at 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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