[Top] [All Lists]

RE: [TowerTalk] Rotator for MA550

To: <>, "'Kim Bottles'" <>
Subject: RE: [TowerTalk] Rotator for MA550
From: "Dick Green WC1M" <>
Date: Thu, 17 Jun 2004 11:10:17 -0400
List-post: <>
I agree that the windload must be considerd. Technically, the MA550 should
be able to handle the 4-el SteppIR. I believe the tower is now rated to
either 60 MPH or 70 MPH with up to 10 sq. ft. of antenna. That said, I
completely agree that the tower should be cranked down when not in use.
That's what I do with my MA-770MDP. It stays all the way down except for
contests and the occasional rare DX that I still need. I have a wind speed
gauge and indicator in the shack, and always lower the tower if the wind
gets much above 25 MPH. Note that my current antenna, a 4-el 20m yagi with
30' boom, has considerably less windload than the TH-7 I used to have on the
tower. The TH-7 is about the same as a 4-el SteppIR. If you saw the tower
with TH-7 swaying back and forth, often violently, when the wind gusts over
about 15 MPH, you'd lower the tower too!

An alternative is to lower the tower to about 40 feet or less. The structure
is much stronger when lowered just 10 feet, and is really strong when
lowered by 20 feet. I used to keep my MA-770MDP at 50 feet and it was pretty
stable at that height with the TH-7. I suspect it would take something on
the order of a hurricane to damage the tower at 40 feet. However, since I
used the antenna so rarely outside of contests, I decided it wasn't worth
keeping it up at all (I have a small tribander on a small guyed mast -- an
AB-577 -- that's quite sufficient for casual use.) Note that the MA-550
would have to belowered to 40' or 30' to get the structural advantages
mentioned above.

I've been considering replacing the monobander with a 4-el SteppIR, and
there's no way the tower would stay up all the time.

BTW, the motorized version of the tower isn't just a luxury. First, the
tower is 250 feet away from the shack down a steep hill. Second, I was
certain that if I had to manually raise and lower the tower I would get lazy
and not lower it when it really needed to be lowered. I think the motor and
remote control are worth every penny.

73, Dick WC1M

> -----Original Message-----
> From: Rick Karlquist [] 
> Sent: Tuesday, June 15, 2004 6:56 PM
> To: Kim Bottles
> Cc:
> Subject: Re: [TowerTalk] Rotator for MA550
> The real issue is probably:
> Is the MA550 strong enough for the Yagi when the wind blows?
> I just bought a 2 element SteppIR for my
> MA-550.  I also have a 4 element SteppIR
> at another QTH on a lattice tower turned by an AlfaSpid.
> I wouldn't want to put the 4 element on the MA-550 unless I 
> was going to crank it down in high winds.
> I used to have a KT34 on the MA550 and a HAM-M
> turned it with no problem.  I didn't leave it up
> in high winds.  I remember that the antenna would
> slip on the mast in high winds, so the HAM-M never
> really got much of a workout.  The rotating base
> structure is specifically designed for the HAM-M
> through HAM-IV rotators, as you can probably figure
> out if you look at it.
> I have 20 year old UBC calcs for the MA-550 and it certainly 
> isn't rated for much antenna area at 70 MPH.
> Rick N6RK
> Kim Bottles said:
> > Gentlemen,
> >
> > I just picked up a used MA550 with rotating base. Is the 
> Ham IV strong 
> > enough to turn this thing? I will be putting my 4 element 
> SteppIR (10 
> > Square feet WL, 80 pounds) on it.
> >
> > What rotator is the "best" solution that will fit the rotating base 
> > fixture?
> >
> > Thanks!
> >
> > Kim Bottles - K7IM
> >
> > Ps. Does anyone have a manual for this MA550 that they would be 
> > willing to copy for me? (I have the drawing from US Tower's 
> website, 
> > but if there is any other information that came with it 
> originally, I 
> > would like to see what it has to say. Thanks again.) 
> > _______________________________________________
> >
> > See:  for "Self Supporting Towers", 
> > "Wireless Weather Stations", and lot's more.  Call Toll Free, 
> > 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
> >
> > _______________________________________________
> > TowerTalk mailing list
> > 
> >
> >
> >

See:  for "Self Supporting Towers", "Wireless Weather 
Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions 
and ask for Sherman, W2FLA.

TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>