[TowerTalk] Rotator cable and mast questions

[Al Kozakiewicz]

When I first read this I thought, "yet another ham overengineering thing".  Then I actually did the engineering.

400' of 12 AWG annealed is 0.635 ohms, whould would drop approximately 2.5 volts at 4 amps.
The same run with 16 AWG would drop about 6.5 volts.
The same run with 10 AWG would drop 1.6 volts.

I came to 2 conclusions:
1. Rotator motors should be designed for 24, or better, 48v!
2. 12/2 is a reasonable compromise, though 10 AWG wire is only about $0.10 per foot more.

Al
AB2ZY

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Andreas Hofmann
Sent: Saturday, December 01, 2012 2:35 AM
To: 'towertalk at contesting.com'
Subject: [TowerTalk] Rotator cable and mast questions

Hi group,



I am in the final stretch of getting my DB18 up onto a MA 550.  Rotator arrived today, its an alfa spid RAK, top mounted.  Questions:



1.       What rotator cable? I am trying to figure out what rotator cable requirements there are. I know it can draw 2 to 4 amps at 12V. My run will be roughly 200 feet from controller to rotator. I am thinking a 12-2 (2 wire 12 gauge) cable and a smaller one for the sensor.  Is 12 gauge adequate for this length?



2.       What mast material? I need a 3 - 4 feet mast below the rotator and another 3.-4 feet mast between rotator and antenna.  Went to Home Depot, they have galvanized 2 inch water pipe (with 1/8 " wall). Is that adequate. Its called schedule 40. In K7LXC's book I read that either "for small antennas or mounted right on top of tower, I can get away with pipe".  Schedule 40 seems to have a yield strength of 30,000 lb/inch^2.    Will this be strong enough for my application?  If not, what are other good places to purchase drawn aluminium tube?  Plumbing supply?





Thanks, Andy

KU7T

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