The Ham IV will probably do the job. I use a Tailtwister on my MA-770MDP
with a 4-el 20m yagi with a 30' boom and it works fine. It also worked fine
for years with a TH-7, the windload and weight of which are very close to
the 4-el SteppIR. When you get the rotating base setup correctly (see below)
you can grab the drive shaft and easily turn the tower and antenna with one
hand. I suspect the Ham IV will fit better than the Tailtwister. The TT is
kinda tall and I had to cut off some of the excess thread from the base
mounting bolts in order to lower the rotor plate enough for the TT to fit.
That wouldn't be necessary with the Ham IV.
As for the rotating base, make sure the tower is plumb (not the base -- the
tube itself.) Do not overtighten the nut on the bolt that connects the short
coupling pipe to the drive shaft. The pipe acts as a poor-man's U-joint
between the rotor and tower, and must be free to swing around on the bolt.
That's why an aircraft nut is used -- it's just there to keep the bolt from
falling out. Also, don't push the rotor jaws too high on the coupling pipe
-- that will restrict its movement. The idea here is that due to the lack of
an upper thrust bearing, it's impossible to make the tower perfectly
concentric with the rotor, so the tower will inevitably bind if there isn't
enough slack in the system.
73, Dick WC1M
> -----Original Message-----
> From: Kim Bottles [mailto:firstname.lastname@example.org]
> Sent: Saturday, June 12, 2004 2:28 PM
> To: email@example.com
> Subject: [TowerTalk] Rotator for MA550
> 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?
> 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: http://www.mscomputer.com 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.
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