[TowerTalk] Antenna Adventures

[Gregg Corsello]

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Date: Sun, 26 Jul 1998 10:20:04 -0400
From: "B. ROHDE - K3XA" <brohde@ibm.net>
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To: Gregg Corsello <quadman@sgi.net>
Subject: Re: quad
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Gregg Corsello wrote:
> 
> Hi, Bill.  Well, first the bad news.  The 6-element quad on the web site
> is now history also, thanks to 89 mph winds we had here on June 30
> (maybe the 3rd time will be the charm)!  I will probably post the
> pictures(of the destroyed 6-el quad) on the site eventually.
>     The good news is that I have (unfortunately) had the opportunity to
> see firsthand how these antennas fail WHEN they fail.  The 6-element had
> components from different quad manufacturers.  Some of them held up.
> Some of them didn't.
>     I still use the AL wire from Lightning Bolt.......for the parasitic
> elements only.  The driven elements were copper stranded from
> Cubex........I had them in the garage and decided to use them.  I would
> use this combination again.  I don't need all the weight (and extra
> expense) from copper wire on the reflector and directors.
>     The 4-el quad was LB out of the box.  One feedline to his xfmr at
> one common feedpoint.  It was a fair performer.
>     The 6-el quad was a combination of Cubex (spiders), LB(16 spreaders,
> AL wire, some spiders), and Max-Gain Systems (8 spreaders).  Coax was
> fed to a remote switch mounted on the boom.  From there I had separate
> feedlines to each driven element.  I had pre-made 1/4 wave sections from
> RG-11 for each band, then checked the whole thing with my buddy's
> MFJ-259 analyzer.  I checked it with AND without the 1/4 wave sections.
> 2 of the bands were actually better without the 1/4 wave sections, so I
> left them off (sorry, I don't remember which ones).  So I ended up
> feeding 3 of the 5 bands with the 1/4 wave sections.  This antenna was a
> MUCH better performer than the first one.  The design was loosely based
> on a QST article from March 1977 (I think) entitled "Evolution of a Quad
> Array".
>     Baluns.......beads......good idea, but I didn't use them.  The next
> one that goes up will probably have a line isolator at the switch box.
>     Bill, I don't know if you already have a quad up, or if you are
> planning on building one.  If the latter, some mechanical considerations
> based on my experiences with component failure:
> -any quad with boom length in excess of 16', I would probably use 3"
> O.D. x AT LEAST .125" wall-thickness boom stock.  I have had 2 booms
> with .063" wall-thickness fail.  They tore like tin cans.  The truss
> didn't seem like it helped at all.  All it did was eliminate boom sag.
> Jay, K6MB, is using a .250" wall-thickness boom on his 4-element quad,
> and so far it has held up well.
> -Max-Gain systems spreaders are better than Lightning Bolt.  I mentioned
> I had 16 Lightning Bolt and 8 Max-Gain spreaders on my 6-element.  Well,
> 15 LB spreaders broke; all 8 Max-Gain came thru intact (I think you
> could beat a tree with those things!).  LB spreaders are $20 apiece;
> Max-Gain are $17.95, which works out to about $20 apiece shipped to your
> door.
> -I have had several LB spiders bend/break when these antenna failed.
> None of the Cubex spiders bent or broke.  Another good source for
> spiders is Antenna Mart.  You could get these (Antenna Mart) through
> Allen at Max-Gain.
> 
> I truly believe, with the use of good components, you could build a quad
> that would stay up in 100MPH winds.
> 
> I hope this has been helpful.
> 
> I will be designing my next quad over the winter.
> 
> 73, de Gregg, K3QK
> Thanks for info Gregg.  I had a 2 el. 20 quad a number of years ago in northern NJ and it was basically a Cubex parts item.  I held up very well in storms, but obviously was just a little 2 el.  I'm now thinking of building a new 4 el for 20-10 and your info and experience is much appreciated.  I'm also in the process of constructing a 2 meter EME antenna and will incorporate some design strength ideas into that project.  I'll be watching for info on your web as the new quad is placed into action.  Hopefully the new design and weather will cooperate for lots of years!  Thanks and GL,  73, Bill/K3XA

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