I would put the 2L40 on TOP for both
electrical and mechanical reasons.
I find that 10, 15, and often 20M antennas SUCK
during midday hours when placed at 70 to 100 ft
compared with lower antennas for those bands.
40M antennas at 70 to 100 ft play VERY WELL
in the late afternoon and evening. The really high
(140 to 200 ft) 40M beams seem to own the
morning LP and very low MUF openings. I'm very
pleased with my 402CD at 95 ft.
A 2L40 has considerably LESS windload than a TH7
so it makes more sense mechanically as well. A
STRONG (>90,000 psi) 2 inch O.D. mast with
wall thickness of 1/4 inch or greater will support
a 2L40 with 10 to 14 ft of separation. I like to have
at least 5 ft of mast inside the tower to minimize
the bending moment applied to the top of the tower.
The primary (only?) electrical difference between
an XM240 and the earlier version of the 2L40 is
that the on the earlier version 402CD, the reflector is
electrically connected to the boom. W1JR
(who designed the early version) recommends
a connecting strap at the center of the reflector
to the boom for the XM240.
Tom N4KG
On Wed, 13 Nov 2002 "Jim W7RY" <w7ry@centurytel.net> writes:
> I know this has been discussed SEVERAL times before... BUT
>
> Has anyone had any REAL success stacking a 2 element Cushcraft 40
> and a
> TH7DX on the same mast ?
>
> I do not want to have 1 rotated 90 degrees.
>
> How far apart did you need to put them ?
>
> Which antenna was on the top of the mast ? Why?
>
> Could you measure the interaction ? How?
>
> The tower will be 70' of Rohn 45 guyed with non metallic
> Phillistran.
>
>
> Thanks and It's been a while since I was here on Tower Talk. Time to
> put up
> another tower after moving from Eastern Washington to Southwest
> Washington.
>
> 73
> Jim W7RY
>
>
>
>
>
> _______________________________________________
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>
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