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[TowerTalk] Cushcraft 40-2CD on 12, 17 & 6m

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Subject: [TowerTalk] Cushcraft 40-2CD on 12, 17 & 6m
From: (DavidC)
Date: Tue, 30 Jun 1998 22:29:14 -0400
> The 40-2CD presents a reasonable match on 17M (<2:1 SWR) 
> and seems to work as an effective  rotary dipole on that band. 
> The SWR on 12M is higher but can be tuned with most antenna
> tuners.  I know many people who use this as their primary 17M
> antenna and a few who also use it on 12M.  It should be possible
> to add a close spaced 12M parasleeve driven element if you want 
> to achieve low 12M SWR without a tuner.

What design-type tuner would you recommend for this sort of application? 
L, T, etc? 
Each has strengths and weaknesses and I am interested in minimal loss and
noise.  I am not up to adding a driven element ... yet!  (Is the auto-tuner
in my TS-690SAT adequate for this task?)

> It would be a simple matter to add 12 and 17 meter reflectors
> (or a trapped reflector a la  A3WS) to achieve 2 effective elements
> on each band.  The fact that there are no elements in front of the
> driven element means that there will be NO destructive interference
> as experienced with 3 or more elements on lower bands.   These 
> additional elements for the WARC bands will NOT affect 40M
> operation.  

OK, these would be approximately 18 and 25 foot reflectors inserted between
the director and 40m reflector?  Hmmm.  Perhaps I can recycle some tubing
from the TH6DXX I have laying around.

What sort of spacing would you suggest as a starting place?  (I don't have
a 40-2CD ... yet ... so I don't have dimensions in hand.)  Cushcraft is
only 25m north of me, perhaps I could beta test these mods for them!

> I have often thought such an option would make an interesting 
> product enhancement for Cushcraft.

What do you suppose this does to wind load, balance at the mast, etc?

BTW:  Someone mentioned here that the newest version of the 40-2CD (XM240)
has a reflector that is isolated from the boom.  What would that offer? 
Should the same be done for these added 12 and 17m reflectors?

Thanks! & 73, DavidC  AA1FA

> 73 / GL,  Tom  N4KG
> .....................................
> >Over the past week several folks have told me that the 40-2CD tunes up
> >nicely and runs real well on 12 and 17, and that according to an 
> >MFJ-259
> >shows a good swr and impedance on 6m (multiple wavelengths I guess!).
> >I would greatly value reports of actual experiences with this antenna 
> >on these non-design frequencies as I move closer to finalizing my
> >plans.
> >
> >These are all secondary bands for me and if this beam will handle them 
> >I will be able to settle on it as adequate for those bands and return my
> >focus to maximizing 10-15-20.
> >
> >This is a wonderful reflector, made so by all herein who love the 
> >hobby and enjoy the sharing of knowledge and experience!   Thanks & 73,
> >AA1FA

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