On 12/16/2011 5:17 AM, Mika Liimatainen wrote:
> Hi
>
> I am currently building a antenna tower and I tought to buy Prosistel
> pst2051 or pst61 rotator.How big the hole should be in rotator plate if I
> need to replace part of it to indicate the direction of the antenna??.
> I could not find any information from the manufacturer's website!
I'm not quite sure what you are asking.
The PST-61 and 71 are physically large (and heavy) rotators. Even on my
older PST-61 the motor needs to be repositioned to fit inside a ROHN
45G. The newer models already have the motors mounted horizontally. I
have never tried to put one into a 25G but I seriously doubt that it'd
fit. I'm not familiar with the PST2501 other than having seen photos of
it on their Internet site.
My PST61 is an older model that had the 110VAC motor mounted vertically.
It had to be rotated 90 degrees to the horizontal and sticks outside the
tower.
The newer models are DC powered, the motor is mounted horizontally, and
they have a shield over the top seal.
Possibly some one else knows whether the 2501 will fit in a 25G.
With the older models the top seal is recessed about 10 mm leaving a
recess in which water can collect, or rather be trapped and corrode the
output shaft. This in turn causes the top seal to fail, followed by the
top bearing. I have not had a chance to examine one of the newer models
to see the construction and implementation of the top seal.
The rotator (PST-61)needs to be removed from the tower to get at the
direction sensor which on mine is just a 10 turn potentiometer mounted
in the base of the housing.
If you ever remove that potentiometer make sure to count the number of
turns from one end of rotation or the other and write it down as you are
only using a turn and a half some where near the middle of the 10 turn
range. It might have been better had they used a 3 turn pot but I doubt
it would be a simple replacement because of the extra resistance either
side of the operating range.
If you are near the sea I'd certainly give the housing a good coat of a
protective paint that would stand up to salt laden air as I've seen
photos of the casings that were severely corroded.
What type of tower are you building?
I'm planning on, or hoping to build a motorized, crank up, tilt over,
heavy duty tower this winter and install it before the ground thaws. I
can only get heavy equipment into the back yard when the ground is
frozen *hard*. Well... I can get it back there, but the last time I had
a bucket truck back there it left tranches over a foot deep and it took
3 years before they didn't show. My wife is also a ham and doesn't mind
the towers and antennas, but she does mind having the yard torn up!
<:-)) Any more it rare for the ground to freeze more than a foot
(~30.5cm) deep. Typical is closer to 6 or 8 inches ( 15 - 20cm) so there
isn't a lot of support and machinery moving over the small area tends to
cause the ground to thaw. Of course snow also causes the ground to thaw.
For those in more temperate climates, the ground can be frozen a foot
deep. We receive a foot of snow and the ground will thaw out under the
snow within 3 to 4 days. Last winter I don't think the ground ever froze
enough that you couldn't dig with a shovel after breaking through a 3 or
4 inch frozen crust. 5 feet down the ground remains a constant 50F plus
regardless of the weather.
73 and good luck,
Roger (K8RI)
> Regards Mika, oh6nvc
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