Hi Jim and others,
Thanks again for the input. The tower is a Tashjian LM-354HD and the mast is a
Tashjian AD-200EH. The mast is 2” OD by .25” wall. It looks like it is
galvanized steel.
I’m going to go with the below setup. I’ll send pics when it’s up! I got the
Steppir assembled yesterday, so next step with be putting the Jk401 together
and the assembling all on the tower.
David K6ZD
> On Nov 24, 2020, at 09:41, Jim Thomson <jim.thom@telus.net> wrote:
>
> Date: Sun, 22 Nov 2020 18:39:24 -0800
> From: David Winarsky <david@winarsky.com>
> To: TowerTalk@contesting.com
> Subject: [TowerTalk] Cut off extra 7 ft of mast or leave it?
>
> <Im putting up my first tower, a LM-354HDSP with a Steppir DB11 and a JK 40
> meter horizontal dipole, both in the same mast. I have a 20 ft 2 in OD mast
> from Tashjian and am wondering whether I should cut off the unused length or
> leave it?
>
> <Karl at Tashjian suggested I install the rotator plate 3 ft below the top of
> the tower and the DB11 2 ft above the top, with the JK40 8 ft above that (10
> ft from the top of the tower). That will leave 7 ft of the mast unused.
>
> <Do you folks recommend I leave the extra 7ft of the mast in place or cut it
> off?
>
> <Appreciate the input and any other comments or suggestions on my plan.
>
> <73,
> <David K6ZD
>
> ## what kind of mast ? what is the OD ? wall thickness ? KSI
> strength of mast. aluminum or steel. is it chromolly or dom, or plane
> jane 35 ksi ?
> Knowing that, simple software calcs to provide bending moment where mast
> enters the tower.
> I would put the rotor plate down six to eight feet. That reduces the
> stress on the top of the tower... by a bunch. Leaving 14 foot above the
> top of the tower. Ok, then put the 40m rotary dipole at the top, or close to
> the top.
> Align the 40m rotary dipole so its inline with the steppir boom. Then
> just do mental math..and either add or subtract 90 degs from your rotor
> indicator dial.
> Depending on snow and ice, and length of the 40m rotary dipole, you might
> require a non conductive overhead truss line on the 40m dipole, hence
> mounting the
> 40m dipole 3-4 feet below top of mast. Remember to cap off the top of the
> mast. DXE sells caps. Then no water running down the inside of the mast.
>
> Jim VE7RF
>
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