[amsat-bb] Re: az-rotor

tokens at myranch.com tokens at myranch.com
Thu Nov 29 12:06:33 PST 2012

Hi Erich et al.,

Following suggestion I did the following. Since the rotor goes beyond 180 on the right side of its travel I let it go until it stopped. I then visually noted how much beyond 180 it had gone, divided by 2 and brought the dial back to 360 plus the number just obtained. I then assumed the pot was at its halfway position. I made the following resistance measurements 1-2 was 209.7 ohms, 2-3 was 206.1 ohms, and 1-3 was 415 ohms. Considering the manual guess work I think that is a pretty good result. I then ran SatPC32 and attempted to park the rotor at 360. It was off, I had to park it at 341 for the rotor to actually be at 360. This is basically the same result as before when I was just going by the control box readings. I believe the resistance measurements would suggest that there is not a short in the pot (unless it just happened to be around the halfway point). 

At this point I am not sure what to try next

73 Al W8KHP

From: Erich Eichmann 
Sent: Thursday, November 29, 2012 1:52 AM
To: tokens at myranch.com 
Cc: amsat-bb at amsat.org 
Subject: Re: az-rotor

 Hello Al,
you wrote:
> The problem is that half way through, when it should read 360 it reads 345. 
> There is a nonlinearity in the readout.

I made and make the same observation with the KR-600X, the AZ rotor of my KR-5600A rotor combination. The KR-600X is completely equal  with  the AZ rotor of the G-5400B combination regarding control box and wire poti in the rotor (Yaesu took over the Kenpro rotor production and replaced the "KR" by "G").  

When I first added rotor control to my tracking software years ago I mounted the  KR-600X in the shack over a big 360° linear scale with 1 m diameter and with a pointer that moved around the scale close above it. The rotor ran exactly an 360° turn from the starting position  180° in the south to the end position 180°. In the software I entered 180 for the start positon and 179.9 for the end position. I could adjust the meter so that it also moved exactly into the start and end position, after I had adjusted the rotor interface poti and the "Out Voltage" poti at the control box. . 

Then I entered 360° (rsp. 0°) as target position. The rotor moved exactly to that position, the pointer pointed exactly to the opposite direction of the starting position.  The meter however pointed to about 342°, so it was wrong by about 15° to 20°. The situation is the same until today. The maximum of the deviation is in the middle of the scale.

So, by my experience and at least in my case the wire poti in the rotor is very linear, but the meter is not. 

I agree with Domenico, that the linearity of the poti is important.  

73s, Erich, DK1TB

  ----- Original Message ----- 
  From: <tokens at myranch.com>
  To: <APBIDDLE at MAILAPS.ORG>; <amsat-bb at amsat.org>
  Sent: Sunday, November 25, 2012 10:00 PM
  Subject: [amsat-bb] Re: G5400B Rotor Problem

  > Alan,
  > Thanks for the answers. The rotor goes through its 360 just fine. The 
  > problem is that half way through, when it should read 360 it reads 345. 
  > There is a nonlinearity in the readout.
  > 73,
  > Al W8KHP

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