[TowerTalk] Mounting 1.25 stinger in 3" tubing?
terry burge
ki7m at comcast.net
Sun Jun 9 02:23:31 EDT 2019
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 at 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 at 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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