Re: Rotator question


For my PST rotator I have added a 'permanently on' heater in the bottom housing.
This always keeps the base (and pot) slightly warm.
No condensation in the bottom of the rotator housing. Seems to work as pots last
a lot longer than they used to. Before fitting the heater I broke open an old
pot and it was noticably wet inside.
which have a drillable plastic shaft, also note the ratings !.
Personnally I prefer to use the cheaper pots which may not last as long as Vishay
or Bourns but you can afford to replace a couple before costs equal them.
I am on my second PST rotator now, long story but thought the first had
failed but turned out to be a broken wire inside the rotator. Bearings on the old one
are completely shot, but as there is also backlash I would only use it as an emergency
spare. Many years of 60 to 90MPH gales with a four yagi EME sysem for 2M would explain
this though.
Martin, GM6VXB

----- Original Message -----
Sent: Tuesday, February 04, 2020 11:29 PM
Subject: Re: [UKMicrowaves] Rotator question

Hello Graham

The problem I found was that the pot was starting to break-up physically.  That seemed to be due to it being directly coupled to the main bearing of the rotator without any vibration isolation. Movements in the antenna system, both laterally and axially, eventually shook the pot apart ...

I'd now always fit some form of flexible coupler between the pot and the rotator drive shaft. I'm doing that with the readout system for my new EME antennas, but there I'm using shaft encoders, rather than pots.

Have you looked to Mouser or DigKey for replacements?


Chris G4DGU

On 04/02/2020 20:43, Graham G3TCT wrote:
Like others, I now have the dreaded PST rotator problem of a pot that indicates any angle except the right one. Second one to fail after ~10 years.  Looking at the options for pots, I find that the Vishay 536-11103 has no IP rating at all, so is vulnerable to moisture ingress.  Bourns make a pot that is IP65 rated -

but the bad news is that this one has a metal shaft that would be very tricky to fit with the pin (not sure I can drill a hole in a metal shaft!).  Bourns also make a IP65 one with a plastic shaft - model 3590S-3-103, but I can't find a source for it - not RS, Farnell, ebay. I might try emailing Farnell to see if they can get one (or maybe a dozen, given others' comments!).
Comments welcome

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