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Subject: Re: [TowerTalk] WHICH ROTOR TO USE?
From: K8RI <>
Date: Sat, 05 May 2012 20:17:52 -0400
List-post: <">>
On 5/5/2012 7:11 PM, Per Molund wrote:
> Hello
> I do not think it is quite fair to compare the largest PST with the small
> CYtorq DX 1500. However, if You compare the PST with the DX Pro 4800 I
> think You will find them quite comparable.
First, no one is comparing the largest PST rotator to the DX1500.  The 
PST-61 is comparable in price (give or take a couple hundred dollars) to 
the DX1500 and it is a long way from being the largest PST rotator being 
followed by the PST61DHP, PST71, and for the well heeled with a large 
tower there is the PST110 which coincidentally I believe weighs 110#
Another nice thing about the PST series is the IIRC  540 degrees of 
rotation.  That makes the PST-61 one of their smaller offerings. You 
won't think that after carrying one up a tower.

The Orion 2800 was one of the other rotators I was trying to think of 
which I believe uses a double worm gear drive and pulse direction 

The Canadian built, AlphaSpid is a great rotator that I believe fits 
inside a 25G has rotational torque of 3200 inch# and holding torque of 
14,000 in #
Price was roughly the same as the Ham IV with a digital control box or 
about $1200. With the current exchange rate I'd guess it to be some 
where between $1400 and $1500.  OTOH I've not heard much about them for 
a while.  They are "I believe" sold stateside by MFJ.

> The CYtorq rotators have quite impressive data regarding accuracy and speed
> and it is nice to see some advance in technology from the old 'dumb' DC
> drive with potmeter as position sensor.
That is proven and reliable, but C-Band (goes way back) dish positioners 
used pulse indicators when I was involved with them nearly 3 decades ago.
>   Looking thru the documentation I
> did not find any reference to wheter this is a open-loop system that can
> get 'out of sync' and have to be recalibrated regularly (ref. SteppIR
> antennas)
C-band positioners could get out of sync, but normally it was only after 
maintenance, so even open loop should not get out of sync often and 
those saw a lot more operating than most antennas except during 
contests.  You could disconnect the whole works for a month or two, hook 
it back up, apply power to the receiver and it would remember where it 
had been set. You actually had to have the receiver disconnected and 
change the direction, or mechanically move the positioner adjustment.

> or they have a closed-loop implementation with a position sensor.
> Also there are no indication of the required number of conductors for the
> rotator cable, since it involves a eight phase stepper I would guess 6
> conductors for the stepper motor alone. From the picture of the controller
> it looks like there is an 8 pin connector for the rotator.
They really need to provide more comprehensive information.  Its ratings 
they do provide make it look ideal for large tribanders, but that short 
full rotation time looks like it could be hard on larger antennas well 
within its ratings.  OTOH it may be variable speed.  It also looks to be 
much easier to install in a 25G.  I'd sure like to see that top seal,  
or get one apart.

Like my other equipment, I'd like to see how they perform after they've 
been on the market and in service for a couple of years.


Roger (K8RI)
> I did not find any information on availability, I understand CYtorq have
> been displayed on some ham shows? Hopefully it is not another 'shipping
> next week' product, hint KX3 :-)
> LA9XKA - Per
> At 23:36 05.05.2012, K8RI wrote:
> 1500 in# of torque and 4500 in# of holding torque limit 25 sq ft of
> antenna. It also has a 30' boom limit. My 7L 6-meter yagi would take
> care of that.
> It's not clear in the photos but I hope that is the top seal and not a
> bearing where they show the rotator mounted to their 25G mounting plate.
>    The PST-61D has 2,150 in# of torque and 16,530 in# of holding torque.
> IE, it doesn't need a brake and is rated for 39 sq ft of antenna.
> Weight 55#
> IE about 43% more torque  2150-1500 = 650/1500=0.43 and almost 4X the
> holding torque and 56% more antenna.
> The heavy duty version PST61DHP has 7,640 in# of torque, the same 16,
> 530 in# of holding torque and is rated for 42 sq ft of antenna(s)Weight 66#
> 5X the rotating torque and 4X holding torque.
> The early PST61s had a top seal problem that is supposed to have been fixed.
>     Be wary of the older ones using the green, AC motor.  You can build a
> shield to keep water off the top seal fairly easy, but they are likely
> to fail if not modified.
> I believe they also are using white Lithium grease now instead of the
> heavy weight gear lube there were using.
> One more point, I don't think you will get one inside a 25G.
> 73
> Roger (K8RI)
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