Peter:
With limited time and already-installed Yagis, let me give you three
suggestions to consider for 40M:
1. Shunt feed the tower on 40M;
2. Hang a half-sloper wire (33.5 feet long +/-) off the tower near the top,
using the Yagi aluminum as a top hat; and
3. Feed the boom of the C31 with a gamma match and use as a dipole at the top
of the tower.
4. Rotatable dipole parallel to the Yagis' booms.
In terms of speed to service, the sloper is quickest, the rotatable dipole
is next and the gamma feeding of the boom is likely the most finicky, with the
shunt-feed nearer to the loaded boom solution in terms of complexity. But the
sloper is something you can try in an hour or so, so you can eliminate it from
consideration pretty quickly.
If you need details, drop me a note. I've used all approaches except the
boom loading at my station (third-acre lot, but most of that is the front yard,
not the back where the tower is.) I can point you to some good sources for
design info.
73 de
Gene Smar AD3F
-------------- Original message ----------------------
From: Peter Dougherty <w2irt@comcast.net>
> Hi again.
>
> Thanks to all who've replied off-list re my grounding questions.
>
> Now, I have another situation that's providing me with more questions
> than answers. I need to correct a bad miscalculation that I made when
> planning my antenna system, and frankly money is now getting somewhat tight.
>
> What's up now is an LM-470 tower with 10' of Aluminum mast. At about
> 2' above the thrust bearing is a C31XR, then at the top is a WARC
> Yagi, (2-2-1 from Force 12, 7' boom). I figured that will give me
> everything I need for 10-30, and so far it's lived up to expectations.
>
> However, I badly miscalculated on how critical a band 40 is. I have
> an Evans 40-80-160 wire configured as an Inverted Vee, apex at the
> 65' mark off the tower. It plays OK on 80 but it's a black hole on
> 40. With 1500W, I typically need 20 or 30 calls to get anything in
> eastern Europe, Russia, etc. Only way to work VK/ZL is to be there
> when nobody else is. I can't break any pile on 40, and I'm getting
> slaughtered every year in CQWW once the sun goes down, and until 80
> opens up. Not just that, but I kill everything in the house with RFI
> (even with ferrites!) on 40 - I'm clean everywhere else.
>
> I need to get something done before CQWW, but frankly I don't know
> which way I should go. I was thinking a BigIR vertical, but I suspect
> QRN will be a problem. Wires just don't cut it from here, as the last
> year has proven conclusively. This is a 1/4 acre suburban lot, and
> the variance I have only allows one tower.
>
> I have a budget of no more than $1500 including installation for
> this. Do I have any hope of a solution?
>
>
>
> Cheers,
>
> Peter,
> W2IRT
>
>
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>
>
>
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