Date: Wed, 17 Mar 2010 00:02:23 EDT
From: NPAlex@aol.com
Subject: [TowerTalk] Prop Pitch motor power
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
tower
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
supply
is in the shack, connect the common to your coax grounds.
Norm W4QN
=======================================
## I was going to proceed to do exactly that, back in 1977,
but my no load V was abt +34 to +36 vdc on the HB Un-regulated
pwr supply. I think the run to the PPM was 175' [350' total loop]
Somebody had given me some 3 x conductor stuff, forget what ga
## The V drop was such, that it worked fine, as my V was on the
high side anyway. Just using the braid only of one coax run, would
also do the trick.. like on a crank up tower. That saves having to use
heavy ga wire on a long run... and up the side of a crank up tower.
## just cranking the V up to compensate for the drop will work too,
or a combo of all these idea's.... but maybe not these days... with
PWM being used.. like in the GH control box. Dunno if the GH box's
PWM will handle the extra V... or if the extra v would screw up the
PWM operation ??
later..... . Jim VE7RF
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