[TowerTalk] Frozen Rotor

[Martin AA6E]

Winter greetings!

With the help of a good antenna guy, I installed a roof-mount tower (20
ft Rohn 25) with a Yaesu G-1000 holding up a 3-el SteppIR on an 8 ft
mast.  Nothing exotic here, but it gets out nicely.

We've had a couple of nights this winter of below 10F.  I've found the
rotor just won't budge until morning, when things warm up into the
teens.  What's going on?

There could be some ice in the tower sleeve.  Is that the most likely? 
Shouldn't the G-1000 be able to break through?  The rotor does not slip
against the mast.  (Indicator does not move.)

What do people do to prevent this?  Lubricate the sleeve, provide a
weather shield, heating tape, ...?

73, Martin AA6E