The new F12 40's are designed to go over or under a tribander, rather
than a WARC beam. Think the new "N" elements have a secondary
resonance around 18 mHz, to keep it out of the hair of 15 meters in a
regular tribander. I wouldn't put an "N" element close to a WARC beam.
But "N" element interaction with regular tribanders is being reported
as zilch.
The CC XM240 has had varying stories (good, bad, and wierd) about
secondary resonances. No one seems to have put their finger on the
authoritative answer to why it's one way here, another there. (Speak
up, y'all, if you've figured it out. The world is waiting.)
On Thu, 28 Oct 1999 14:55:21 -0500, you wrote:
>
>75' is a little low for optimum performance for 40M DX, but it will sure
>beat the heck out a sloper.
People keep saying that, but the models show a nasty null in a common
arrival angle at 100', with a lot of power lost in a secondary lobe
aimed at 70 degrees above horizon. 130'-140' is good for
beginning/ending of openings, half that for when the band is open and
strong. Commonly reported that the lower of a 40m stack is best for
mid openings. And if you are contesting all band, single op, you
should never be opening or closing a band.
Mine is going up at 81 feet, and if the trees were lower, it would go
at 73'
>I would look at the new force 12 40M elements
>that are 85% of full length. I do know if they have adopted them for the
>EF-240 yet, but when they do take a look at that. If you can model and feel
>good about no interaction, the Cushcraft XM 240 works well, too.
>
>73 John N5CQ
>
>-----Original Message-----
>From: owner-towertalk@contesting.com
>[mailto:owner-towertalk@contesting.com]On Behalf Of Brian Smithson
>Sent: Thursday, October 28, 1999 2:34 PM
>To: towertalk@contesting.com
>Subject: [TowerTalk] 40m beams
>
>
>Hi all!
>
>As the base for my 2nd Trylon cures, I'm contemplating the
>beams. I have 24' of 1/4" 4130 that will leave 16' sticking
>out the top. I plan on a 12/17 beam on top and I'd like a
>reasonable signal on 40. I have a C31XR on the first tower
>that works great.
>
>I'm struggling with my options. I have no experience home-
>brewing beams but until a year ago, I could say the same
>about tower installation!
>
>I've heard good things about the 2 and 3 element F12
>designs, as well as Cushcraft. It has also been suggested
>that I consider homebrewing a full-size 2el 40.
>
>I thought I'd post a query to the TT experts - what would
>you do if you were putting a single 40m beam at 75'? What
>do you think about the linearly-loaded designs vs. full-
>sized? I'm interested in the trade-offs in gain, bandwidth,
>and rotor-load.
>
>Any thoughts?
>
>Thanks, and see you in WW!
>
>-brian n8wrl
>
>
>--
>FAQ on WWW: http://www.contesting.com/towertalkfaq.html
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--. .-..
73, Guy
Guy Olinger, K2AV
k2av@contesting.com
Apex, NC, USA
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
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