[TowerTalk] Resistance of Rotor Control Wires (see also CAT5 thread)

[Guy Molinari]

I use 10 conductor sprinkler wire (Lowes' or HomeDepot) for the 300+' runs to my M2 rotators.   2 groups of 4 conductors tied together for the motor control lines.   The 2 remaining conductors are for the reed switch sense lines.    
73,Guy, N7ZG

> Date: Thu, 26 Jul 2012 14:44:01 -0700
> From: lwloen at gmail.com
> To: towertalk at contesting.com
> Subject: [TowerTalk] Resistance of Rotor Control Wires (see also CAT5 thread)
> 
> I am trying to understand control wire (DC) resistance losses.  This
> would be for my rotor control wire for my M2 atop my
> soon-to-be-erected 72 foot tower.
> 
> I figure my total run is going to be fairly long -- about 215 feet
> (for a variety of reasons, a straight cable run is not in the cards --
> I have to go around my septic field and a shed).  The specs for the M2
> rotor http://www.arraysolutions.com/Products/m2rotators.htm . . .show
> the minimum cable gauges are 2 at number 18 and 2 at number 22.  This
> probably relates to the total amperage delivered and the planned
> voltage drop the unit can stand.
> 
> Calculations given here:
> http://www.stealth316.com/2-wire-resistance.htm  . . .are suggestive
> that I would want more like number 12 gauge if I wanted to keep the
> voltage loss to half a volt (apparently, the M2 design can stand a bit
> more?).  There are a couple of other sources, including this one:
> http://www.mogami.com/e/cad/wire-gauge.html   which, while it
> dispenses with the "circular mills" part of the calculations (at least
> overtly) seems to me to create a similar conclusion.
> 
> This suggests to me that I should be looking at some hefty cable
> gauges if I want to be "really sure" of things working, but I get the
> impression that this is probably overkill, given what M2 itself seems
> to be recommending.  A 72 foot tower would have a minimum run (if one
> wanted to keep the shack out of the fall zone) of about 150 feet for a
> 75 foot total tower exposure.  And, I know M2s are popular with
> VHF/UHF hams, where a lot of towers are taller still.  I'm sure lots
> of M2s have 200 plus foot runs.
> 
> Still, in line with my overengineering of the project, what I probably
> would find ideal is some sort of four wire shielded cable at somewhere
> between 12 and 16 gauge if I could find such a thing.  Or, would
> unshielded with a couple of ferrite beads at nor near the rotor be
> enough?  That would simplify things quiet a bit.
> 
> CAT cable looks suspiciously narrow gauge for my run, at least.
> 
> 
> Larry Wo0Z
> _______________________________________________
> 
> 
> 
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk