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Author Topic: High band, multiband array  (Read 687 times)
NN3W
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Posts: 147




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« on: June 04, 2007, 09:07:50 AM »

Hey, I've been thinking about revising my high band system.

I live in a association neighborhood, although they really don't seem to care.  In fact, the three associtation neighbors bordering me are indeed supportive of my work - I passed messages for one while he was doing Mission work in the Dominican Republic.  Unfortunately, the major restriction on antenna "growth" is the XYL.  She absolutely refuses permission for a real tower, and scoffs at the notion that putting something up high actually removes it from the visual field.

Anyhow, my main benefit to the property are trees.  I've got about 8 - 10 white oaks, red oaks, and poplars.  All are mature, and many are up to 80 feet in height.  I've put up a full wave quad for 80, and a 2 element delta loop array on 40 - all supported by the trees.  

However, I'm using a different tree for a 20 meter delta which is broadside NE/SW.  I don't like it very much as it covers 20 fine, but performs poorly on 10 and cannot be tuned for 15.

I've considered a 20 meter 4 square (too much expense with the switching/phase lines and radials), a MA5B on a Radio Shack 37' mast, a 2 element used Lightning Boltquad on the same Radio Shack 37' mast, a Hexbeam (commercial 5 band version is WAY too expensive), and fixed 2 element delta loop array.

I really can't use any ladder line fed antennas as the risk to the kids with the voltage is too high, and the tree stand is a significant distance from the shack.

Thoughts?
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NN3W
Member

Posts: 147




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« Reply #1 on: June 04, 2007, 09:12:18 AM »

Followup...

BTW, I prefer something that can handle a bit of power.  The TH3jrs which has an ideal turning radius (I cant be more than about 14' turn radius) handles only about 500 watts - I'd fry that easily.
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WB2WIK
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« Reply #2 on: June 04, 2007, 09:58:11 AM »

If you're surrounded by 80' tall trees, I don't think you're going to be happy with a beam at 37'.  I know from my own experience living with mature trees, I sure wouldn't be.

If your wife scoffs at a high beam or tower being out of the visual plane and thus less noticeable, you should ask her to close her eyes and tell you what the tops of all your tall trees look like.  She won't be able to, because nobody looks up there.  A 100' tower and beams rotating completely above all those tall trees won't be seen by anyone unless they're flying over in a helicopter.

However, it does sound like *cost* is an issue as well, and 100' towers aren't free.

Of the stuff you listed as possible prospects for a low beam, the Lightning Bolt Quad probably works best but may be the most trouble to install and keep up.  The 5-band Hexbeam's not bad, either.  Problem withe the MA-5B is it's finnicky and easily detuned by surrounding objects, and also has no gain on 12m or 17m.  I'd want something that really works like a beam on those bands, especially as 17m is currently a premier DX band with a lot of activity.  12m becomes one, and will again in a few years.

Not sure I'd install this stuff on a 37' extendable mast, unless that mast were house-bracketed at 20' and also guyed very well to supplement the brackets. And then, it's still a bit risky -- these masts were intended for lightweight TV antennas having no more wind surface area than about 1.5 square feet.

If you need to go "short," I'd recommend four sections of Rohn 25G to get you up 40 feet.  Anchor it properly, bracket it to the house and guy the top, and you'll have a secure structure you won't have to worry about in windstorms.  And it's cheap, especially used.

WB2WIK/6
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NN3W
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Posts: 147




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« Reply #3 on: June 05, 2007, 08:19:23 PM »

Thanks for the reply.  Anything mounted to or attached to the house is going to be a non-starter - mostly from the XYL.

I've got a clearing in the trees which gives me enough clearing for about 14 foot turning radius.  

I had considered a Mosley TA33jr, but the traps are marginal on handling 800 watts.  I've heard that Mosley does offer a beefed up version - the MP33 which weighs the same as the 33jr, but handles a full gallon power wise.

Other contenders, again, include the Spider Beam and the Hexbeam.
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KB5DPE
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Posts: 298




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« Reply #4 on: June 19, 2007, 11:25:06 AM »

"She absolutely refuses permission"

Permission?  PERMISSION???
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W3LK
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Posts: 5639




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« Reply #5 on: June 19, 2007, 11:36:09 AM »

My thoughts, too.

What a shame. My wife just picked out our retirement home and she made sure there is room for my antennas and new tower - and she doesn't care two hoots about radio, but she DOES care about me and my interests.

FWIW, she doesn't give me "permission" to do anything. We respect each other's hobbies and are free to indulge tham however we each see fit.

40 years together last month and going strong.

Lon - W3LK
Baltimore, Maryland - Soon to be Naugatuck, Connecticut.
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
W3LK
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Posts: 5639




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« Reply #6 on: June 19, 2007, 11:36:40 AM »

PS - She pulls coax, too!!!

Lon - W3LK
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
WK0F
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Posts: 46




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« Reply #7 on: June 20, 2007, 01:01:52 PM »

I highly recommend the Hexbeam.  I think you will find it will disappear with the trees in the background.  It has a very small turning radius, and should handle the legal limit.  I know they are pretty spendy.  If you are good at building, you may want to consider joining the yahoo group, http://groups.yahoo.com/group/hex-beam/
They have a lot of members who have built their own at lot less than the cost of a commercial Hex.  Remember, the Hex is a two element wire beam so it probably won't be a pile up buster at 37 feet. FWIW!
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N3BIF
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Posts: 1190




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« Reply #8 on: June 22, 2007, 09:22:39 AM »

 You also can build it with only your bands of interest if you want to simplify. The one I made was single band for 20 and was pretty easy to put together with mostly pvc and string. At 30 feet it didn't show any real gain benefit but did exhibit directivity.
    After a month or so It was cannibalized for other projects. Once I can add another 10 feet  to the mast I plan to give it another go.
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