On Mon, 28 Dec 1998 21:17:12 -0600 "John T. Duncan" <jduncan@nol.net>
writes:
>
>
>I am considering stacking a KT34XA, 12/17 duo-bander and Cushcraft
>2el 40 in that order with the tribander on the bottom on a 20 ft mast
>(16ft =out of top of tower). I thought I had it all figured out by
keeping
>the tribander and 40m beam as far apart as possible...But NO.....
>
>Now I have read a couple of reports of interaction between 17 and 40 =
>meters! Apparently one of the 40m elements is 1/2 wavelength at
>18mhz.
> WA5ZVE
.......................
The CUSHCRAFT 2L40 works well on 17M with an SWR around 2:1
The LOADING COILS are positioned very close to 1/2 WL at 17M.
My hunch is that the coils, and the associated capacity hat, provides
enough isolation for the elements to appear near resonant at 17M.
If that is the case, it would be a simple matter to place a 17M reflector
8 ft behind the driven element to achieve a 2L 17M beam on the same
boom and feedline.
Placing a parasleeve 12M element close to the 40M driven element
and a 12M reflector 6 ft behind the 12M parasleeve driven element
would give you a 2L 12M antenna also on the same boom and
feedline.
It may take to adjustment to find the correct spacing for the parasleeve
element, but I would love for someone to try this approach and let
us know how it works.
A separate 12M monobander and a 17M reflector on the CC 2L40
is another option.
Admittedly, such an arrangement will be unbalanced mechanically.
The new beefed up Cushcraft with the stronger 2.5 inch boom would
be a better candidate to handle this extra load.
(OK, I admit it, I'm lazy and it's cold outside so I'm not about to
take down my Cushcraft 2L40 to try it for myself. Maybe if / when
it needs servicing, but not before :-)
de Tom N4KG
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