[amsat-bb] Home brewing El. Az. rotators

Gaston BERTELS gaston.bertels at skynet.be
Wed Sep 12 01:21:11 PDT 2007

Hi folks,

Tony did a great job building his AZ-EL tracking system.

I have also done some work on this, building a 
lightweight system with a couple of motors from 
motorized car windows and discarded bicycle parts.

I have used an acetylene welder and manufactured 
a tool for forming helicoïdals out of 8mm 
diameter steel rods you can find in DIY shops. 
These helicoïdals drive the bicycle chainwheels. 
The AZ-EL booms are welded on the axes of the chainwheels.

The tracking sensors are microswitches moved by 
the teeth of the chainwheels. Zeroing the AZ-EL 
positioning is done by a second pair of 
microswitches sensing a 180 degrees semicircular 
rod epoxied to the chainwheels.

I have written the adhoc tracking software in 
Delphi. The electrical interface is a kit sold by 
a popular electronics editor (Elektuur). It uses an USB port.

This lightweight system is very rugged. Angular 
precision of AZ-EL positioning is limited to 
about 8 degrees, due to the chainwheel teeth 
sensing. This is sufficient for tracking the ISS 
with 145MHz crossed yagis.

Gaston - ON4WF


At 03:50 11/09/2007, Tony VK5ZAI wrote:
Hi Guys,
Seems a lot of talk about rotators lately, have you thought about
building up your own, I did this around 15 years 
ago and the system has
never been switched off apart from twice when moving QTH and the
occasional service, greasing etc. My present QTH is 300 yds from the
Southern Ocean and we get some almighty winds in 
the winter but it keeps
on going. It's driven by 2 windshield wiper 
motors and constructed of
parts that can generally be scrounged from 
vehicle and machinery junk
yards etc. You will require a small welder to put 
it together and access
to a lathe but really there's no great precision required in it's
construction. I've described it's construction on my web site listed
below. hopefully it will be of interest to some of you.

Regards Tony.  VK5ZAI

P.O.Box 470 Kingston SE
South Australia  5275

National ARISS Co-ordinator
and Satellite ground Station.

Web Site :-

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Gaston Bertels, ON4WF
ARISS-Europe Chairman

Avenue Paul Hymans 117 B29
B-1200   Brussels, Belgium

Phone :	+32.2.771.67.74
Mobile: 	+32.476.215.124
Fax :	+32.2.771.49.89
E-mail :	gaston.bertels at skynet.be

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