Larry,
Download the M2 Orion 2800 manual. They provide a table of recommend
wires size(s) versus distance.
For 200-300' 14AWG is suggested.
Larger is better, or course....
According to page 8 of the Orion manual Wireman makes a 2x12AWG +
2x18AWG shielded cable for these rotators. This is Wireman's #306 cable,
according to their website. I have not yet contacted the vendor to
determine actual availability.
I am in the midst of a similar project with about a 300 ft cable run.
best regards
John N7ZN
On 7/26/2012 2:44 PM, Larry Loen wrote:
> 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
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