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I've been considering a EF-180S myself at ~80' and am beginning to think even that won't be high enough. Some options for you: 1) the Sigma 80 is supposed to be ready (80m vertical) 2) a titanex vertical (might be blasphemy on this forum, but it's an option) or compromises like butternut, MFJ, etc. 3) shunt feed the tower for 80 4) low cost wire antenna dipole/inv v/inv L/T/... solution Of course, none of these give you directivity (which is maybe what you're gunning for with a rot dipole). You might consider phased verticals in that case or separate (directional) receiving antennas (small loops, beverages, arrays/k9ay, etc.). Given your low height, the bang for the buck wouldn't seem to be worth it with the EF-180S on a 33' tower (to me). The nice dipole lobes/nulls would be reduced to a terrible pattern (esp for DX). I hadn't heard the 12' rule, but have read where folks are using EF-180s stacked closer than that. Where did you see that Steve? While most of what I'm going by here is based on talking with folks rather than first hand experience, I've been going through a similar planning excerise (at the 70-80 foot level). Good luck either way, Pat N0HR Quoting K7LXC@aol.com: > In a message dated 9/5/01 10:07:15 PM Pacific Daylight Time, > list@qth.com writes: > > > I have a chance to get a US tower TMM-433HD. The tower has a height of 3'w/ > > o Mast and can handle 24 sq. ft. at 50mph. > > > > So I would like to put up a C-4SXL (40-10meter beam)and a EF-180S 80/73mtr > > Rotated dipole, and finally a small 6 meter beam. The total would be about > > 14sq. ft. > > > > My questions are: > > 1. Does this seem like a good configuration? Is there enough height for > > these antennas. I live in the desert so there is pleanty of space and > > clearance, my main concern is will an 80mtr dipole work at that height? > > The first question you need to answer is "what is your county windspeed > rating?" You can find out from the website <A > HREF="http://www.championradio.com">www.championradio.com</A> under Tech > > Notes. The minimum rating is 70 MPH which will downrate the 50 MPH wind > pressure figure significantly. I just installed a MA-850MDP which is rated at > 10 sq.ft. @ 50 MPH but was only rated at a 25 pound load in the PE > drawing calculations at 80 MPH. > > As far as the configuration, F12 wants 12 feet separation between the > antennas so now you need a significant mast. > > > > 2. How would the antennas be arranged? C-4SXL on bottom then EF-180S in > > middle and then the 6mtr on top or should it be the other way around? > > > I'd go 6M at top, EF-180 and then the C4; that'll be the easiest on > the mast. > > > 3. Finally, since there are 4 feed lines should I use some kind of > switchbox > > at the tower or just run 4 cables to a manual switchbox in the > shack? > > > Your call. Personally I prefer straight to the shack since that'll > eliminate a potential failure in the feedline system. The costs are > probably similar anyway. > > Cheers, Steve K7LXC > Tower Tech > Champion Radio Products > --------------------------------------------------------------- Get Free Internet Access And WebEmail At http://www.address.com -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Web sites: http://www.qth.com/force12 and http://www.force12inc.com Submissions: send to Force12Talk@qth.com To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk For problems with the list, contact n4zr@qth.com |
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