[amsat-bb] Re: az-rotor

HB9OMQ hb9omq at bluewin.ch
Thu Nov 29 14:25:22 PST 2012

To eliminate the position pot from the circuit substitute it with
two fixed resistors, ie. 220 Ohm 1/4 Watt. By connecting terminal 2 to 1,
2 to 3 and 2 to the middle point of the to resistors you my simulate -180°
and +180°. You my also use more resistors, for more positions.
Then adjust the out voltage for 5V reading when the terminal 2 is connected
to 1 and
the meter for full scale reading 180° South. Leave the Out output open, no
interface connected.
If you connect then Terminal 2 to the middle point of the resistors, you
should read 2.5V
at the Out output and 360° on the scale.
As suggested, the position pot is fed by a 7806 Voltage Regulator, which may


-----Ursprüngliche Nachricht-----
Von: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org]Im
Auftrag von tokens at myranch.com
Gesendet: Donnerstag, 29. November 2012 21:07
An: Erich Eichmann
Cc: amsat-bb at amsat.org
Betreff: [amsat-bb] Re: az-rotor

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
> 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

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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