HAM-4 ROTOR TROUBLESHOOTING ADVICE

[Tony Brock-Fisher]

HOLD ON A MINUTE!!!

I think some folks don't understand what the capacitor does!!

It is NOT a motor starting capacitor!!!

The purpose of the cap is to cause a 90 degree phase shift
across the windings of the motor, which determines which
direction the motor wiill turn.

Some old capacitors dry out and the value changes. This does result
in the motor not starting to turn. Replacing the cap will make
the motor work again. But replace it with the same value!!
We have to assume Hygain/CDR knew what they were doing when
picking the value. A larger value cap will allow more current
to flow, but will also affect the phase angle, which will actually
decrease the starting torque! An infinitely big cap would be a short!
Do you think the motor would like that??

And while I'm up here on the soapbox, I'm scratching my head trying
to figure out how you can get away with back-to-back electrolytics?
That combo would still have o DC bias across it, so the electrolytic
would not be happy.

The best idea I've heard yet is to move the cap directly to the rotator,
properly weatherproofed of course. This eliminates the cable resistance
inseries with the cap. Now use the two wires in the cable which went to
the cap, and double up on the motor wires, cutting the resistance
down there two.

If anybody's interested, I've got some ideas on how to run Hygain
rotators on 4 conductor cable. That way you could go 2-for-1 rotators
on the same cable...

-Tony, K1KP, fisher@hp-and2.an.hp.com

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