[TowerTalk] rotor @ 200m distance

[Jim Thomson]

Date: Sat, 14 Oct 2017 10:08:38 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] rotor @ 200m distance

On 10/14/2017 9:44 AM, Filipe Lopes wrote:
> My question is regarding the rotor, what kind of cable or how should one
> rotate the rotor at such distance? I guess the voltage drop is quite high,
> meaning the rotor will turn very very slowly or even not turn at all.

<Ohm's Law is your friend, but Yaesu's tech data is not. :) They don't 
give you a maximum permitted resistance so you must compute it. I have a 
350 ft run on my Yaesu rotator. I had to figure conductor resistance for 
their maximum recommended cable length based on its conductor size, then 
do Ohm's Law with a wire table to know what wire size to use. One 
important piece of information -- study the schematic of whatever 
rototor you are using. With the Yaesu, two conductors run the motor, the 
other three sense the position of a simple potentiometer that tells 
direction. Only the motor pair is sensitive to resistance. I ended up 
using #14 "house wire" for the motor pair and #18 for the potentiometer.

73, Jim K9YC

##  he has to go 200M  to base of tower....then up the tower, plus rotor loop. 
say 230 M in total  =  755 feet..which is a bunch.   He will require  10 gauge
wire for the pair of motor leads. 

##  Too bad rotor makers didnt offer a tap on the xfmr..for a higher voltage,
for longer runs.    That option is included on the M2  OR-2800  rotor  control
box.  The sec of the xfmr has  2 taps, low + high.  Default was low V.   High was
only used for long runs.   I think the high was  42 volts. 

##  another possible option is to insert  a correct value of voltage in series with  one or
both motor leads.   Or better yet, insert it in one of the sec leads of the xfmr.   Seems silly
to have to use huge gauge wire.   But no doubt there will be a max vdc or vac limit going
up a tower, for legal liability reasons.  IMO,   50-55 vdc  would be ideal for rotor motors,
vs  wire gauge.   Nobody got electrocuted in any Telco with  -52 vdc. 

Jim  VE7RF