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For my PST rotator I have added a 'permanently on'
heater in the bottom housing.
This always keeps the base (and pot) slightly
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
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
----- Original Message -----
Sent: Tuesday, February 04, 2020 11:29
Subject: Re: [UKMicrowaves] Rotator
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?
On 04/02/2020 20:43, Graham G3TCT wrote:
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 -
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'