Jeff,
I found when building my 40 meter 4-square weight was a big problem when
raising and lowering 32-34' verticals. I bought my tubing from DXEngineering,
mostly 0.120" thick wall aluminum. But the top 15' or so I used 2" irrigation
tubing. That helped when raising and lowering for doing the needed adjustments.
A lot of adjustments to get the dump power down. Going from 3" X 0.120" X 144"
to 2" irrigation tubing took progressively smaller diameter sections. A lot of
6' pieces of course. I used between 1' overlap down to 5" or so as I recall
except for maybe the 2" irrigation top piece. Made sure I could have enough to
adjust the resonance to where I needed it. Turned out some VERY strong, well
build verticals as you can see on my www.qrz.com/KI7M page and used Comtek
4-square setup. Works pretty well but 4-squares are a different breed of animal
to tune up. You sort of forget about the SWR and go by dump power. Awhile back
I got 3-4 S-units front to back which definitely made me happy.
Hope this helps you in your plans.
Terry
KI7M
> On June 8, 2019 at 12:44 PM Mpridesti via TowerTalk
> <towertalk@contesting.com> wrote:
>
>
> Jeff
>
> Should be no issue using dramatically different diameters and I believe
> modeling programs will give the additional length required for resonance.
>
> Anytime you have a step in diameter, you have lengthen the overall element to
> compensate.
>
> Just guessing, you probably need 2 or 3 ft more of element length to offset
> the 3 inch to 1.25 inch transition.
>
> Others here can be more precise.
>
> Regards,
>
> Mark, K1RX
>
>
> > On Jun 8, 2019, at 12:08 PM, Jeff Blaine <KeepWalking188@ac0c.com> wrote:
> >
> > I'm rebuilding my 40m 4-sq verts and have some 15' lengths of 3" OD/ 2.75
> > ID tubing to use on the base end. And for the "stinger" end, I have some
> > tapered elements off an old yagi that are 1.25" OD on the bottom of the 17'
> > length.
> >
> > Other than buying some concentric lengths of aluminum to step from the 1.25
> > OD stinger up to the 2.75 ID base tubing, any good ideas of an interposer
> > that would take up some of the space?
> >
> > 73/jeff/ac0c
> > alpha-charlie-zero-charlie
> > www.ac0c.com
> >
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> >
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