There were several good responses to the question below - I have been using
a prop pitch motor rotator for nearly 40 years with great success. Most
power supplies are located in the shack and feed cable wire size is a key
part of the supply voltage equation. My power supply delivers about 30
volts at the source and drops to 22-23 volts at the motor. I now use a Green
Heron/ K7NV controller and with the pulse width ramp up and down of source
voltage solves the inertia problem of large arrays.
There is a trick of wiring that can reduce the voltage drop to the motor
for tower base mounted power supplies, and also works for shack located
supplies. The prop pitch motor is a three wire device, common lead with a
forward and reverse set of leads. The common lead can be grounded to the
at the PPM end and the power supply end as well. If you ground the coax
shields at the top of the tower and again at the base of the tower (good
practice for lightning protection) they two will form a parallel conductive
path along with the tower itself to the common wire lead. This can
significantly reduce the voltage drop of the total feed line. If the power
is in the shack, connect the common to your coax grounds.
In a message dated 3/14/2010 9:58:38 P.M. Central Daylight Time,
What is the maximum DC voltage used successfully/recommended for one of
the "small" PPM's ? What speed was accomplished and how was the brush
at that voltage ?
I 'm building a power supply to put at the base of the tower and can
change the voltage from about 30 to 48 volts in 6 volt steps. Cable to
be 100 feet of 3-#12's. I'm figuring about 0.5 ohms and about a ten amp
demand i.e. a 5 volt drop.
Any suggestions will be greatly appreciated.
Gene / W2LU
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