[TowerTalk] Prop Pitch motor power

[Commtekman at aol.com]

Norm,
Great idea on the grounding, I had not thought of that and I have been  
using PP motors since the late
50's. Thank you for the info-
 
Bob K6OSM
 
 
 
 
In a message dated 3/16/2010 10:02:50 P.M. Mountain Daylight Time,  
NPAlex at aol.com writes:


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
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In a  message  dated 3/14/2010 9:58:38 P.M. Central Daylight Time,    
w2lu at rochester.rr.com writes:

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 
 
life 
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  
PPM will 
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.
Thanks,
Gene /    W2LU
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