Tower Help

[K7LXC at aol.com]

In a message dated 96-02-08 11:39:54 EST, you write:

>A few years ago ROHN published a nice manual with engineering data on their
>tower line. Not only the ham stuff like the 25/45/55, but even the
>commercial stuff. It had their factory engineering data as well as guy
>design recommendations, concrete base specs, even dead-man design. I never
>used it for such, but I suspect copies of those pages would have overwhelmed
>the average county building permit clerk, provided you intended building to
>those specs. It also had maps showing what areas of the CONUS were rated for
>the different wind threat levels, so you could determine exactly which set
>of standards you should be constructing for. No guesswork, just good
>engineering-based design stuff.
>
>I don't know if it is still available, but it sure would be a worthwhile
>addition to any ham's library. It was free for the asking back then.
>
>Jerry       W4UKU      South Carolina     flanders at groupz.net
>
>
>

Jerry, howdy --

   Yes -- the Rohn catalog(s) is the FIRST thing that I recommend that anyone
contemplating any tower installation obtain.  They produce 2 catalogs: one
for Consumer Products (BX, 25G through 55G and SSV) and a Commercial Products
version that covers everything except BX.  They are available from Rohn
(309-697-4400) or from most Rohn dealers.  They are $10 from Rohn with a
voucher toward the purchase of Rohn products so you get your $10 back.

   Both of the catalogs have a bountiful supply of specifications relating to
wind loading, guy anchors, bases, hardware, tools, etc.  The latest versions
have been updated to TIA-222-E (the industry standard) as well as 110 MPH
wind charts.

   EVERY HAM should have one.


73, Steve  K7LXC


             "Up The Tower"    now appears in CQ Contest magazine

>From Pete Smith <n4zr at ix.netcom.com>  Thu Feb  8 18:49:09 1996
From: Pete Smith <n4zr at ix.netcom.com> (Pete Smith)
Date: Thu, 8 Feb 1996 10:49:09 -0800
Subject: Tribander stack/spacing
Message-ID: <199602081849.KAA29576 at ix5.ix.netcom.com>

I've been messing with EZNEC, modeling stacked C-3s at various spacings (top
antenna at 97-102 ft), and the results indicate that while the stacking gain
may be relatively constant over a fairly wide range of spacings, the pattern
formed by the stack is anything but.  Some spacings produce definitely
enhanced patterns at one frequency (14 mHz and 37 feet, for example, or 21
mHz and 25 feet), while others have a devastating effect on the pattern (21
mHz and 37 feet, for example -- note the problem?).  

If anyone wants the details, I'll be glad to provide them  -- as well as the
C-3 model).

I've checked what I have from the amateur literature, and the closest thing
to describing what I'm seeing is the the K8CC article on stacking dissimilar
yagis in NCJ a few years back.  K1VR and N6BV seem to like 30-foot spacing,
but my models using that spacing don't look particularly good.  Maybe that
is the best compromise available, particularly to cover 20-10 meters, but
what about for the next couple of years?

I really have two questions:

To what extent are these spacing effects dependent on particular tribanders,
or are they generically true?

If they are generic, can anyone suggest a spacing that might be a better
compromise between 20 and 15 (ignoring 10 for now) than the 30-foot one?
I'm pretty well stuck with having the top antenna between 97 and 102 ft, by
the way.

Thanks for your help.  Please reply direct, and I'll summarize if there is
interest.