Thanks, Guy. I also got a private communication that included the
manual (gee, read the manual, who'd have thought?). The manual
suggests that I'd want 14 gauge wire for the main rotor control and
still 22 or 24 for the reed relays. It also suggested a rule of thumb
that if I wired two 16 gauge together in parallel, it would be the
equivalent of 13 gauge and (though it doesn't say so) that four 16
gauge together would be (presumably) 10. So, if I go by the M2
manual, I presume your scheme works provided the sprinkler cable was
in the 20 gauge range. Neat trick, I'll consider it.
Larry Wo0Z
On Thu, Jul 26, 2012 at 2:52 PM, Guy Molinari <guy_molinari@hotmail.com> wrote:
>
> 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@gmail.com
>> To: towertalk@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
>> _______________________________________________
>>
>>
>>
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