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[TowerTalk] 40 Meter Beams

To: <>
Subject: [TowerTalk] 40 Meter Beams
From: (
Date: Tue, 25 Nov 1997 10:52:31 -0500 (EST)
In a message dated 97-11-25 01:04:39 EST, writes:

> I went for the KLM 40M4 and I'm glad I did. It replaced my Cushcraft 402CD,
>  and it is a better-abled performer.
    Really? I had just the opposite experience. I got rid of my KLM 4L 40M
beam and replaced it with a 402CD. I've never regretted it. I didn't think
the KLM ever played like the big monobander that it is and never felt like I
gave away that much in terms of performance. The 402CD is MUCH MORE reliable.

>  I've never had a problem mechanically. Of course, I went to some extra
>  trouble in that effort, by drilling and riveting all sections together,
>  by adding a short stay across the middle of the boom to hold the
>  side trusses. This keeps the whole thing from wiggling around and falling
>  apart in the wind.

    I had lots of mechanical problems in spite of reinforcing at element
brackets, 120 degree boom guying, etc. ANY big antenna is a fragile antenna.
The KLM broke somewhere every year and it was a major project to get it down,
fix it and re-install it. You had to round up have 4-5 people to help too. I
ALWAYS recommend the Cushcraft over the KLM.

     How long has yours been up? Suffolk County is an 85 MPH wind speed zone
plus you're within 100 miles of hurricane oceanline so if you haven't seen
BIG winds yet - you will. 

     Anyone who's considering putting up a big 40M antenna is looking at big
cost, big rotator and a big rigging challenge (you're talking 200-300
pounds). Here's an option. How about a 2-stack of 402CD's? Just about the
same performance, a nice fat lobe on the horizon, less hassle and cost (Ham
IV's instead of a prop pitch for one). 

    As far as Wayne's original question, I'd go for a 3L linear loaded
antenna or maybe even a full-sized 2L. The Force 12 antennas are EITHER phone
or cw - they don't have enough bandwidth for both. On the plus side, it's
only a medium-sized antenna and isn't a huge load on the tower or rotator. I
haven't seen a linear loaded M2 antenna. I installed a full-sized M2 3L (140
MPH version) at AI6V and it was a brute. You need a dedicated tower for this

     I think the incremental improvement by going to a 4L (the KLM is only
really 3 remember - it has dual driven elements) isn't worth the cost or
increased tower stress. Run some models of 2 and 3 element versions and see
what the differences really are. Most knowledgeable antenna folks that I've
talked to preferred the 3L but I think a full-sized 2L might be worthwhile.
Then you can go out and either find one or build one. 

73,  Steve  K7LXC


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