[Top] [All Lists]

[TowerTalk] Orion--the final word

To: <>
Subject: [TowerTalk] Orion--the final word
From: (Chris R. Burger)
Date: Fri, 16 May 1997 19:59:25 +200
A few weeks ago, I asked about Orion rotators, and the requirements 
for fancy cabling.  A new Orion owner told me that the factory 
recommended two shielded #22 conductors for the pickup circuits, and 
three heavier conductors for the motor.

I posted a question, soliciting experiences with these rotors.


*  Several were using runs up to 500' without problems, using 
   standard multi-core cables.  In some instances, Belden 8 core 
   rotator cable was being used, with pairs carrying the heavier 
   current (i.e. two cores for pickup, 2 x 3 cores for motor drive).

*  One reported AC pickup problems while using an A/D converter to 
   read the position off a HyGain rotator (in a homebrew controller).  
   The solution was an active low pass filter.

*  Several reported problems with moisture in the connector, which 
   caused major indicator problems.  Apparently, even minor 
   condensation in the connector up on the tower would cause wildly 
   erratic readings.

While I have not seen the manual for the OR2800P, I believe that the 
positioning system actually uses a pulsing encoder with a counter 
(rather than an analogue system).  If that is true, the A/D converter 
problem should not be relevant to the Orion.  The moisture in the 
connector could cause trouble, as a very high impedance circuit like 
that would require very little leakage to get confused.

I just got off the phone to Mike Staal, one of the Ms of M-Squared 
(and formerly the M in KLM) and the technical driving force behind 
the company.  He says:

The pickup problem is definitely only a problem on very long runs 
(over 300').  The problem is with counting pulses (on the position 
indicator) being coupled back into the counter circuit.

Solution:  Use a single coaxial cable for the pickup.  The cable 
carries around 100 uA, so its conductor guage is not critical.  The 
mechanical manageability of having a surviveable cable in the duct 
will probably dictate the dimensions.  Suitable solutions include 
RG58 and audio cable (the very thin stuff, around 1 mm diameter).

Chris R. Burger

PS:  For those with traditional values, 1 mm = 13/331", or 27/686" 
in round figures.

PPS:  Yes, I know how the Ancient system works.  You might even 5/128" 
if that is more comfortable to you, or even 1/32" if that is close 

PPPS:  Yes, that is my idea of a joke.

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>
  • [TowerTalk] Orion--the final word, Chris R. Burger <=