[TowerTalk] Experience with MA550 tower

Wed May 7 23:01:12 EDT 2008

I have a 3-section Wilson MT-61B crankup tubular tower, which is not installed - it's just lying on the ground as I don't have any particular plans for it right now. I just looked through the manual for it, and then went out and actually looked at it - it doesn't appear to have any kind of steel pins anywhere, just the single raising cable. I also had the 40-foot tall 2-section version of the same Wilson tubular tower about 16-17 years ago, same thing. I did have it braced against the house with a bracket, and it worked out well with a 2-element tribander quad on it. If I remember correctly, Wilson also made a 77-foot, 4-section version of this tubular tower.

I also have the RB-61B Rotor Base/Raising Fixture manual for this MT-61B Tower (but not the actual fixture), and the manual for the companion GK-61B Guy Kit. Looking through the TT archives and following the related discussions, it seems that the US Towers MA-550 is the modern replacement for the Wilson MT-61B. The top section of the MA-550 is a square tube, while the Wilson top section was round, and maybe a few other design changes. I believe I saw info about people ordering the MA-550 series raising fixture, rotor base, etc. from UST to use with their older Wilson MT-61B.

The GK-61B Guying Kit manual specifies four guy wires going to the top of the tubular tower. The pictorial on the front page shows the tower being used with the RB-61B Rotor Base/Raising fixture, out in the clear, away from any buildings. 

A couple of notes that make me hesitant to try to guy any of these tubular towers though - these notes are from the GK-61B guying kit manual (dated 06/01/80):

"NOTE: With this Guy Kit properly installed the tower is capable of supporting a 20 sq. ft. antenna at 80 mph."
"Do not over tighten guy cables. Leave enough slack so tower top can move about 1 ft. from vertical."

It sounds to me like the single set of guys are just loosely attached, and will hopefully keep the tower from falling over if the wind blows TOO hard! It doesn't look like a very encouraging, stable way to support an antenna. This is one of those situations where I don't know if I'd really want to "Do what the manufacturer suggests", by guying a lightweight tower like these. 

If Wilson was still in the tower manufacturing business, I have doubts that they'd still be offering this guying kit. If I wanted a guyed tower, I think I'd find a way to go with Rohn 45, or similar.

LJ

-----Original Message-----
>From: Dick Green WC1M <wc1m at msn.com>
>Sent: May 7, 2008 10:20 PM
>To: "'larryjspammenot at teleport.com'" <larryj at teleport.com>, towertalk at contesting.com
>Subject: Re: [TowerTalk] Experience with MA550 tower
>
>The MA-550 cannot be guyed and there's no kit for it. Guy wires would exert substantial downward force on the tower, and all of this force would be borne solely by the wire rope cables that raise and lower the tower and provide all support for the structure when it's raised. The greater the wind, the greater the downward force. I don't know the specific numbers, but would imagine even a modest wind could exceed the breaking strength of the cables.
>
>Though I've never seen one, I have a manual for one of the Wilson tubular towers. They had steel pins to support the tubes independently of the cables. After raising the tower, the pins would click into place and you could slack off the cables. Then the guys could be tensioned, exerting their force on the pins, not the cables. For lowering, you would slack the guys, then operate a mechanism that would pull out the pins (I imagine you had to crank up the tower slightly to take the pressure off the pins.) Then you could lower the tower. Obviously, this design was intended for leaving the tower up most of the time, rather than raising and lowering it frequently. It certainly wouldn't be compatible with the US Tower motorized raising/lowering and remote control systems, and I suspect most of US Tower's tubular tower customers buy the product because they don't want a guyed tower.
>
>73, Dick WC1M
>
>> -----Original Message-----
>> From: larryjspammenot at teleport.com [mailto:larryj at teleport.com]
>> Sent: Wednesday, May 07, 2008 12:19 PM
>> To: towertalk at contesting.com
>> Subject: Re: [TowerTalk] Experience with MA550 tower
>> 
>> I don't know just how exact the old discontinued Wilson MT-61 tower is
>> compared to the UST MA-550. I've seen several articles that say
>> they're basically the same tower, can use the same raising fixtures
>> and other accessories.
>> 
>> Someone sent me .pdf files of the installation manual about a year ago
>> for the MT-61 and a separate manual for the optional guying system for
>> it. Maybe there's some similar guying method available for the MA-550?
>> 
>> LJ
>> 
>> 
>> 
>> 
>> -----Original Message-----
>> >From: K7LXC at aol.com
>> >Sent: May 7, 2008 9:02 AM
>> >To: towertalk at contesting.com, gdslagel at yahoo.com
>> >Subject: Re: [TowerTalk] Experience with MA550 tower
>> >
>> >
>> >In a message dated 4/29/2008 8:37:00 A.M. Pacific Daylight Time,
>> >towertalk-request at contesting.com writes:
>> >
>> >>  Anyone have favorable/unfavorable comments about this  tower?
>> >
>> >    On the plus side, aesthetically they're pretty  reasonable. This
>> is a
>> >light-duty tower with a limited amount of capacity. If  you live in a
>> windy area,
>> >I'd be pretty careful.
>> >
>> >>  I'm thinking of a used one and, looking at the 4 eham  reviews,
>> there's a
>> >lot of talk about moving towers and needing to add guy  wires.
>> >
>> >    Huh?!? Where does the manufacturer specify  guy-wires? More
>> amateur
>> >engineering. :-(  My advice is to follow the LXC  Prime Directive to
>> "DO what the
>> >manufacturer says." The reverse is also  true.
>> >
>> >Cheers,
>> >Steve    K7LXC
>> >TOWER TECH -
>> >Professional tower services for hams
>> >Cell: 206-890-4188
>> >