C. Sadler,
Did you spin the antenna by hand? Did you feel any binding or high
spots? If so you could have a bearing that's going, if so you need to remove
the belt to see if it's in the antenna part or the motor. Is there a way to
grease or oil the rotating parts, I'd check with the manufacturer on this? I
admit that I don't know radar systems, but I'm familiar with stepper motors.
They're generally not used it this type of application, they're used as far
as I know to turn the motor shaft a certain amount of degrees, usually in
either direction and at variable speeds to position things. I'd suspect that
you have a regular DC motor designed or geared to a specific rpm.
Paul

"C. Sadler" wrote in message
m...
I've got a unit that is about 7 years old.
Recently, it started turning erratically, causing the display to
pop the Antenna not rotating message, and shutting off.

The antenna's turning, but slows about every 1 to 1.5 revolutions.

I've changed the belt, and had a good look at the unit. It appears
clean, and uncorroded.
I'd like to suspect the stepper motor, as that would be a pretty cheap
fix, but before I go there, I'd like to hear some opinions of what
else might
be causing the stepper to speed up and slow down like that.

TIA