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Re: [TowerTalk] AB-577

To: "'Tower and HF antenna construction topics.'" <>
Subject: Re: [TowerTalk] AB-577
From: "Dick Green WC1M" <>
Reply-to:, "Tower and HF antenna construction topics." <>
Date: Tue, 20 Apr 2010 01:42:23 -0400
List-post: <">>
I have three AB-577s, one with a homemade (to spec) extension kit, so I'm
quite familiar with them. 

There are a few odd things about the one listed on ebay, so I would urge
caution for anyone interested in buying it. 

First and most important, you should know that the stock mast goes to 48
feet, not 60'. The kit offered for sale appears to be an incomplete
collection of parts from two or more AB-577s that have been put together to
get the extra height. The stock guy anchors are installed 30 feet out, which
is the default distance measured by the supplied measuring rope. It's
already pretty close for a 48-footer (60% of height), and in my opinion way
too close for a 60-footer. I would push the guys out to at least 40', if not
50' (the rope can also measure that distance because it's used for the
extension kit -- see below.) Even then, I doubt the mast would meet its
original engineering specs at 60 feet with only three guy sets. The clamps
used to mate the tubes are not very rugged and can't take a lot of lateral
force. The greater the distance between the guys, the more lateral force
will be on the clamps. Also, it may be very difficult, or even hazardous, to
erect the unit with that much distance between the guys. Before final
tension is applied, the mast behaves much like a wet noodle. The greater the
vertical distance between the guys, the more exaggerated this effect will
be. This tends to get worse the larger the antenna.

It appears that the original installation manual does not come with this
unit. I would urge anyone buying it to get a copy of the manual and read it
carefully (there are probably some scans online.) The installation procedure
should be followed to the letter to ensure safety of all personnel and

Additional information:

The stock AB-577 comes with eight 5-foot tubes, which is the maximum number
the portable carrier will hold. The five tubes with the 8-foot launcher
gives you 48 feet. It also comes with two different guy rings, one for the
top guys and one for the middle guys, plus an antenna adapter. The three
guys anchors are installed 30 feet from the base. 

The extension kit comes in its own plastic carrying case (that's the one
piece I don't have.) The kit adds five more tubes, for a total height of
73'. Also included are an additional guy ring, two more guy sets and three
more screw-in guy anchors. The stock bottom and middle guys remain at their
stock positions and still run to the stock anchors 30' out. The longer of
the two new guy sets replaces the stock top guy set. The other guy set is
installed halfway between the top and stock middle guy, using the additional
guy ring. The two new guy sets attach to the extension anchors, which are
installed 50 feet out. So you end up with four sets of guys, the lower two
sets anchored at 30 feet out and the upper two sets anchored at 50 feet out.

The non-standard height of the unit for sale on ebay, and the fact that it
comes with two launchers, two carriers and three middle guy rings, makes me
suspect that it's a combination of at least two AB-577 sets. It appears to
be missing two standard parts: the top guy ring and the antenna adapter.
Without those parts, one of the middle guy rings would have to be used for
the top guys, and that would require putting an unguyed tube above the top
guy ring. It's not safe to put an antenna at the top of that (again, the
ring clamp can't take the lateral force), so the antenna would have to be
placed at the bottom of the top tube with some sort of homemade adapter (the
stock antenna adapter has a short piece of ~2" mast welded to it that's
perfect for mounting an antenna bracket or a rotor bottom bracket.) I think
this might explain the discrepancy between the description, which says it
comes with 11 tubes, and the parts list which says it comes with 12 tubes.
The top tube, for all intents, gives you no additional height.

The unit is also lacking the canvas roll, used for storing and carrying the
anchor stakes, sledge hammer and claw bar (the latter two also appear to be
missing, but that's not unusual). It's also missing the canvas bag used for
carrying the guys sets, rings, clamps, etc. I don't see the "winch spanner"
listed, either. This is a special tool that can be used to rotate the mast
after it's been erected (the guy rings slip to allow this.)

The original AB-577 guy sets came with 1/8" stainless steel guys.
Refurbished models usually have plastic-coated galvanized aircraft cable.
Stainless guys work better with the "snubbers" used for tensioning the guys,
but the plastic-coated guys do work (my two 48-footers have plastic guys but
someday I'll replace them with stainless.)
As for the price, I'd certainly pay $650 for a complete 48' kit, but it
really depends on the condition of the parts, especially the clamps, which
tend to wear out with repeated use, and the guy sets. The collection of
parts offered on ebay is probably worth $650-$800 if the parts are in decent
condition --  the extra launcher, tubes and middle guy rings are worth money
for sure. But I'd look into sourcing as many of the missing parts as
possible, specifically the top guy ring and antenna adapter. If the plan is
to take it over 48', I would also get three additional screw-in anchors and
an additional long guy set (or make one using the snubbers from a shorter
guy set.) Ontario Surplus ( has most
of the missing parts in stock. They also have a few complete 48' kits
available, so you can compare the price.

73, Dick WC1M

> -----Original Message-----
> From: Neil & Heather []
> Sent: Monday, April 19, 2010 5:15 PM
> To:
> Subject: [TowerTalk] AB-577
> a055241
> These are getting harder and harder to find.....
> posted for those interested.....
> 73
> Neil
> AE1P


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