I suggest that we all give Frank a round of applause for his excellent
posting.
1. He made an effort to solve his problem by consulting the antenna book
and by making measurements before posting.
2. He clearly described what he needed to know.
Sadly, some of the postings here indicate that the poster is simply
too lazy to check the ARRL handbook or antenna book, and the TT
archives. He wants someone else to do the work for him. A significant
number of questions asked here have been asked before and discussed at
length in the recent past on TT.
I am happy to see that Frank got a quick, complete, answer to his
question.
73, Dan, N5AR
Brian Alsop wrote:
>
> Frank,
>
> My experience with this antenna is that it shifts hundreds of Khz from near
> ground to about 70 feet.
>
> The manual dimensions are quite close to the actuaal needed.
>
> Here they are: 72 3/4",44",44",18 1/2", a (half element starting from center
> of
> element)
> cap hat located 8 1/4" from end of trap assenbly
>
> a = 76" , 74", 72",68" for 7030,7080,7130,7230 Khz
> overall length 42'7",42'3", 41'11",41'3" for same
>
> Unlike other rotary dipoles (or beams) the CC d40 and 402cd are set and
> forget.
> The manual dimensions work. There really is no fine tuning required in my
> experience.
>
> 73 de Brian/k3ko
>
> Frank Norton KB8XU wrote:
>
> > Hello TT'ians,
> >
> > A request for help concerning assembly and adjustment of Cushcraft 40 meter
> > Rotatable Dipole:
> >
> > I found one of the older model Cushcraft 40M Rotatable Dipoles that Tom,
> > N4KG mentioned to me in a prior email. I can't locate specific
> > instructions for this antenna. (the cushcraft tech site lists the manual
> > but when u download it, it is the manual for the multiband dipole with all
> > the traps--not much help.)
> >
> > So anyway here r the details: I have it at 12 feet or so off the
> > ground--best I can do for testing. I got the following SWR curve after
> > carefully adjusting length from the center insulator to the trap and the
> > trap to the tip. Here are the SWR numbers I get: 6.975=1.91, [I know it's
> > out of the band but I had to know ;-).]
> > 7.025=1.45, 7.100=1.45, 7.150=1.81, 7.200= 2.39, 7.250=3.00,
> > 7.299=3.66. So all this appears to tell me is that at 12 feet above
> > ground the dipole has best SWR/resonance at about 7.050.
> >
> > I know that as we raise it in height the resonant frequency should go up. I
> > don't recall the equation; seems it was 25 kHz for ? feet increase AGL But
> > will it resonate in the area of 7.100-7.150 where I need it to? It will
> > ultimately rest at 60 feet above ground--but once it's up, that's it I
> > can't work on it. (I wud have to hire someone again, or impose once again
> > on the family lives of my friends.)
> >
> > Isn't there some way to figure this ahead of time? As stated above, I
> > think there is a ratio of feet or wavelengths above ground to the kHz the
> > antenna will go up in resonance. But my MS plays tricks on my memory. Can
> > anyone help me out? Anyone recall the equation/ratio, if it even exists?
> >
> > I've checked the ARRL Antenna Book 19th Edition but cud not locate the ratio
> >
> > Tnx in advance,
> >
> > Frank, KB8XU
> >
> > List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
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> > -----
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> > Administrative requests: towertalk-REQUEST@contesting.com
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>
> List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
> Trylon Titan towers, coax, hardline and more. Also check out our self
> supporting towers up to 96 feet for under $1500!! http://www.anwireless.com
>
> -----
> FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 96 feet for under $1500!! http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
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