SARCTRAC Mk1 History, Credits and Features

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SARCTRAC Mk1 History, Credits and Features

Published by Julie & Joe in SARCTRAC Mk1 · Saturday 24 Aug 2019
The purpose of this Forum is to inform readers of SARCTRAC software release version history; to credit the authors of any contributing software and to provide user's discussion on new features.

SARCTRAC Software Version History:

Release 1.0 - 8 April 2019: Original Release.

This is the initial release of SARCTRAC after 15 months of solid development effort. SARCTRAC is written in Python. The distributed version is cross-compiled into C++.

SARCTRAC does the all the satellite tracking, antenna steering and transceiver (rig) control automatically, so that students can just enjoy working satellites!
  • It is best suited to portable operation, mounted on a sturdy tripod and attached to a small hand-held, dual-band satellite antenna.
  • It can be set up quickly in the school playground and runs off the same power supply (13.8VDC) as the rig.
  • It uses 3D sensors and DC motors to point the antenna at the selected satellite and does not require any on-site calibration.
  • It has a built-in GPS receiver, to get accurate time and location information.
  • It has a built-in World Magnetic Model, to get the local magnetic inclination and declination.
  • It has a built-in WiFi web server, so students can control it via a web browser on their mobile devices.
  • It has a built-in satellite transponder / beacon database, so students can select the correct satellite frequency and mode.
  • It uses the latest orbital prediction models to accurately track selected satellites.
  • It can automatically download the latest satellite orbital elements from the Internet, using a personal WiFi hotspot on the mobile device.
  • It allows students to select the satellites they want to track.
  • It displays the system status and the next pass of each satellite.
  • It automatically schedules the tracking of each selected satellite in turn.
  • It controls the frequency and mode(including manual fine tuning) of an Amateur Radio transceiver via a USB cable.

Version 1.01 - 28 April 2019: This is a mandatory safety update. So please install it before using SARCTRAC!

WARNING: Safety Issue with SARCTRAC Version 1.0.
SARCTRAC was originally designed to power up and just start tracking. However, if something goes wrong your setup (e.g. if the 3D Sensor was mounted incorrectly), the rotator could move in an unexpected way on power-up, potentially causing damage or harm. By the time you open the SARCTRAC SELECTION page and press the STOP button, it may be too late! To avert this scenario, SARCTRAC Version 1.01 now powers up with the motors stopped. There are also some other important changes in this update as well:

Software changes:
  • Fixed some issues with calibration not always beeping and Doppler frequency tracking.
  • Substantially reduced RFI from I2C bus by reducing the 3D Sensor baudrate.
  • Some DC Motor PID and 3D Sensor LPF changes for smoother operation and easier calibration.
  • Added 3D Sensor auto-reset function, as the 3D Sensor can be affected by stray RF.

Hardware changes:
  • Recommend using overall-shielded cable for the 3D Sensor. However we have not found a suitably-thin cable yet.
  • Recommend soldering 0.1uF capacitors from the motor terminals to the chassis to reduce commutator noise.

Please see the SARCTRAC Manual Version 1.01 for details of the software update process and the new hardware modifications.

Version 1.04 - 26 April 2020
  • As a result of updating to pyephem Version the next_pass function caused exceptions
  • So globally changed next_pass(orbit) to next_pass(orbit,False)
  • On 18/8/2019 Brandon Rhodes updated pyephem next_pass code adding a parameter called singlepass
  • When singlepass is True, next_pass attempts to make a copy of the observer object
  • SARCTRAC's home class inherits the pyephem observer class (with additional parameters)
  • and this copy fails because it doesn't have as many.
  • Nevermind: Setting singlepass to False reverts next_pass to the original code which still works.
  • Created a next_pass variable to avoid repeated calls to the next_pass function

Credit and thanks for included free, open-source software (Please see the following websites for copyright notices and original source code):

New Features:
The following new features, improvements and fixes are being considered for future versions of SARCTRAC:

  1. Brandon Rhodes has depricated pyEphem - although it will still be available on PyPI. Oh well... We wrote our original orbital element propegator in 1985 by translating the "Spacetrack Report #3" FORTRAN-IV code into Pascal. That was fun! Recently we have been thinking of using the C code from "Spacetrack Report #3 Revisited", but it does not include Brandon's future-pass algorithm, which is pretty cool. We have also noticed some Doppler frequency anomalies, which must be based on erroneous range-rate calculations. We were thinking an update may fix this.
  2. SARCTRAC currently supports only the Yaesu FT-817/818/857/897 all mode all band amateur radio transceivers. We considered using HAMLIB, but that is overkill and has its own problems. So we intend to provide more generic support for the following radios:
    1. ICOM CI-V control.
    2. YAESU CAT control.
  3. We are working on a USB WiFi dongle to provide a wireless interface to the radio.
  4. We are working on a higher-gain, dual band, RHCP Yagi specifically designed for SARCTRAC.

Latest News:
31 October 2020: We are pleased to announce that SARCTRAC Mk1 has now been superseded by SARCTRAC Mk2, a fully assembled, calibrated and tested product, with many of the proposed new features and more. See for details.

Julie and Joe
Sunday 01 Nov 2020
Hi Matt,
It has been a long time coming, but we now have a product which will work with a wide range of radios via HAMLIB. See If you are still in 9V1 you would be on the absolute satellite co-visibility horizon for us here in VK3. It would be great to have a QSO. Try our new on-line satellite pass prediction tool to see how far you can go: In September 2015 we were invited by Jeff 9V1AS to give a talk at the Singapore Amateur Radio and Transmitting Society (SARTS). We also activated Bukit Timah for the first time for Summits On The Air. It was great fun setting up - for us and the monkeys! We had to get permission and permits from everyone, of course. Wouldn't it be great to do it via satellite! Keep safe and keep in touch.
73, Julie VK3FOWL and Joe VK3YSP.
Matt Howard
Wednesday 24 Jun 2020
9V1MH here
Really great stuff - love the concept. I have been working with the Scouts here and this would be a great thing for the annual JOTA gathering.
Portable ops is our best way to get satellites here as most of us have no land/roof to work with.
Most of the team here have ICOM radios - is there any timeline on CI-V interface?
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