Rotator Mk2 - SARCNET

School Amateur Radio Club Network
School Amateur Radio Club Network
School Amateur Radio Club Network
School Amateur Radio Club Network
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Mini Satellite-Antenna Rotator Mk2a
In the May 2016 edition of Amateur Radio magazine, we published this article describing the design and construction of a mini satellite-antenna rotator. It used some small DC motors and a novel combination of 3D magnetometers and accelerometers to provide absolute azimuth and elevation feedback. Note: This is a complex DIY project for the advanced kit constructor. Want a fully assembled, tested and calibrated unit? See SARCTRAC.

The original rotator was designed for quick set-up and portable operation at our primary school Amateur Radio clubs. It is very light-duty and can only be used with a small, dual-band, hand-held antenna. Some readers asked us if the rotator could be scaled up for a larger, permanent satellite antenna installation at home. Specifically, one which could handle two, much longer, cross-polarised Yagis, for 2m and 70cm, mounted on either side of the rotator.

This article published in the October 2017 edition of Amateur Radio magazine describes the mechanical design and construction of our Mini Satellite-Antenna Rotator Mk2a. This version is controlled in the same way and uses the same software, set-to-work and calibration as the Mk1 Version.

The full construction details published in a PDF document can be found here. For a version using pulleys and timing belts instead of sprockets and roller-chain see the Mini Satellite-Antenna Rotator Mk2b below. The Arduino source code is here.

Important: Some readers have reported that Globalindustrial no longer stock the Tritan roller-chain and sprockets. Please try searching on for the following parts:  “25-1R X 10FT”, “25-1R CL”, “25BS10H X 1/4” and “25BS32H X 1”. They appear to be available from a seller called Globalpower. Unfortunately on-going supply of parts for our projects is outside of our control.

Important: We no longer recommend building the RS-485 long haul link. Some readers have reported that it is very susceptible to RF and Voltage Spikes, which may destroy the RS-485 drivers. An alternative solution may be to use a pair of APC220 Radio Communications Modules to provide a wireless link. One APC220 module is wired to the Arduino Pro Micro. The other module is connected to the PC via the USB-TTL Serial Converter supplied. Note: We have not tested this solution. Please contact us if you have.
APC220 Radio Communication Modules

APC220 Radio Communication Module Wiring

Mini Satellite-Antenna Rotator Mk2a
Mini Satellite-Antenna Rotator Mk2b
And now for a real surprise! Mark, Technical Director of MiniKits, has come up with a brilliant solution for those, like us who don't live in the US, and who are finding it hard to source the sprockets and roller-chain. Mark has found a very cheap source of 25mm and 6mm bore pulleys and timing belts on eBay. The assembly is shown below. Mark is using 25mm PVC tubing for the shafts just to test the set up. It looks like a fine idea and should be strong enough to handle a pair of counter-balanced, 3m long, yagis.

For the time being, there is no assembly drawing of the Mini Satellite-Antenna Rotator Mk2b. The position of the motor mounting will change at the very least. We won't know until we order some pulleys and give it a try. Thanks again Mark for a terrific idea!

Mini Satellite-Antenna Rotator Mk2b Parts List:
  • 2 x Pulley XL10T 6mm bore (A$2.96 each)
  • 2 x Pulley XL30T 25mm bore (A$9.39 each)
  • 2 x Timing Belt 100XL, 254mm perimeter, 50 teeth, 9.53mm wide 5.08mm pitch (A$1.55 each)

Tip: Search on eBay for the above parts, but be very carefull checking the type and bore size.

Mini Satellite-Antenna Rotator Mk2b

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