School Amateur Radio Club Network
School Amateur Radio Club Network
School Amateur Radio Club Network
School Amateur Radio Club Network
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SARCTRAC - Satellite Antenna Rotator Controller and TRACker
Introducing SARCTRAC, our new Satellite Antenna Rotator Controller and TRACker project, a fully integrated satellite tracking system for portable operation. Simply mount it on a tripod, attach a directional antenna and radio transceiver, then use your WiFi enabled mobile device to select your favorite satellites: SARCTRAC points the antenna at the satellite and controls the radio transceiver so you can listen to space beacons, download earth images, decode telemetry and make two-way satellite contacts. It's both fun and educational!

The inspiration for SARCTRAC was to help little kids have fun in space: Well, at least to play with things in low earth orbit! You might be surprised just how many tiny cube-sats and regular polar-orbiting satellites there are. The first challenge is to know when are where the satellites will be. Then to point a hand-held antenna up at them for about 10 minutes while they pass overhead. You also have to constantly adjust your radio transmitter and receiver frequencies to compensate for something called Doppler shift. It turned out that our young radio enthusiasts found all that quite challenging, which detracted from the fun of getting to know our new friends in space. It was hard for us, too, just getting everything to work at different schools: So we set about to design a fully automated system.

We first introduced our free, Arduino-based, "Mini Satellite-Antenna Rotator" in 2015. It was a great success, with over 600 radio enthusiasts from around the world building one. Unfortunately, sourcing the correct components, compiling and uploading the software was too much for many who attempted building it. Let alone the pitfalls of setting up and using   third-party, satellite-tracking software. And, as much as we love helping our readers out, we realised that we were spending more time supporting them than developing new projects for the kids.

We have now solved that problem by designing an integrated system that just works: SARCTRAC took us over a 15 months to develop and is the second generation of our 3D-Sensor based antenna rotator. It is half the size of the original unit with many new features. It is still a DIY kit, for the experienced builder, but it has a 59-page manual covering assembly, setup, operation and troubleshooting. Once built, all you have to do is mount the unit on a tripod, attach a small, counterbalanced antenna, connect it to a radio and power, and control it from any mobile device. We use it all the time now. It's really easy.

We are offering SARCTRAC as a complete kit of parts or as a software-only download. For more details please see our Products page.
  • Setup
    • Tripod-mounted for portable operation and quick set-up - Easily splits into two separate pieces: Tripod/rotator and antenna/lift-arm.
    • DC powered for battery or solar operation - Typically uses the same power source as the radio.
    • Integrated rotator and controller in one unit - Smaller with less cables. No third-party tracking software to wrestle with.
    • Weather proofing possible - IP68 sensor and IP65 case with neoprene O-ring motor shaft seals. DIY seal around connectors with silicone sealant.
  • Networking
    • WiFi enabled - Works with home WiFi network or WiFi-enabled mobile device with personal hotspot and broadband Internet connection.
    • Internet enabled - Automatically downloads date, time and satellite orbital elements from the Internet.
    • WiFi enabled mobile device used for control and display - No cables to separate PC or laptop.
    • Built-in web server accessible by any web browser on the WiFi network - No tracking applications to install and configure.
  • Start-up
    • Displays satellite SELECTION, satellite TRACKING and radio TUNING web pages - Logically organised pages.
    • Start-up alert tones - Warn of disconnected USB CAT Cable, GPS or 3D Sensor.
    • Access to START/STOP, RESTART and SHUTDOWN buttons on each web page - Important for rotator safety and tracker control.
    • Starts with motors stopped - Operator action is required to start motors after power up for safety.
    • Displays Local Time with Time Zone selection - Easier for scheduling.
    • Date and time information provided by built-in GPS receiver or Internet time source - No clock setting required.
    • Latitude and Longitude information provided by built-in GPS receiver - No station location entry required.
    • Uses last saved location until GPS is available - Quicker startup.
    • Stops polling GPS when location error is minimised -   Reduces processor load.
    • Displays reverse geocode address lookup - Confirms that the correct latitude and longitude is used.
    • Antenna pointing information provided by boom-mounted 3D Sensor (magnetometer/accelerometer) - No compass calibration or leveling required.
    • Magnetic inclination and declination information provided by built-in World Magnetic Model - No online searching for local magnetic offsets.
    • Satellite orbital element information updated from Internet each day - No manual download required.
    • Satellite position determined from the latest SGP4 orbital predication models - More accurate tracking.
    • Uses last saved satellite selection - Quicker startup.
  • Satellite Selection
    • Access to thousands of satellite orbital elements over the Internet - Distributed by Dr. T.S. Kelso at since 1985.
    • Permits user-entry of selected orbital element library URLs - Select which satellite libraries are of interest.
    • Each orbital element library contains hundreds of satellites in different categories, like weather, cube-sats, amateur and NOAA - Select only the categories you want.
    • Permits loading of user-defined orbital element library files - Load pre-launch or unlisted orbital elements.
    • Permits user entry of satellite names to be rejected - Omit whole series of unwanted satellites from the satellite selection list.
    • Displays satellite statistics: Number of each type loaded, duplicates removed, number rejected and the total available - Helps manage your satellite database.
  • Satellite Tracking
    • Tracks only selected satellites - Schedules tracking of each satellite in turn.
    • Selected satellites displayed in order of their Acquisition Of Signal (AOS) time - Provides a next pass schedule.
    • Visible satellites displayed in order of Loss Of Signal (LOS) time - Provides a best pass schedule.
    • Displays next-pass, AOS time, azimuth and max elevation for each selected satellite - Easy to decide which satellite passes to track.
    • Displays currently tracked satellite azimuth, current elevation and LOS time - Easy to compare current satellite LOS time with next satellite AOS time.
    • Automatically points the antenna at a visible satellite - No manual antenna steering required.
    • Built-in 3-second alert tone indicates immanent antenna movement - Safer operation. Alerts at the start and end of the current pass.
    • Intelligent search algorithm selects the best visible satellite to track - Only tracks the longest passes.
    • Permits selection of any one of multiple visible satellites - Compare and select the best of the currently visible passes.
    • Automatically re-positions antenna ready for the next pass - No waiting at the start of each pass.
    • Intelligent anti-windup algorithm - Unwinds the cables in between passes.
    • Tracks multiple selected satellites in turn - No resetting selections between passes.
  • Radio Control
    • Radio CAT control enabled - Automatically controls the radio frequencies and modes.
    • Automatically controls the radio frequencies correcting for satellite Doppler shift - Accurate frequency control.
    • Satellite beacon/transponder frequency and mode information provided by built-in satellite database - No online searching for satellite data.
    • Permits selection of known satellite beacons or transponders - Useful to check the beacon frequency if the transponder is not heard.
    • Permits manual adjustment of transmit and receive frequencies and modes - Useful to avoid interference and use the transponder bandwidth more efficiently.
  • Sensor Calibration
    • One-Time 3D Sensor calibration required - Recalibration not usually required.
    • Provides manual Start, Abort and Save calibration controls with tone feedback - Easier and more accurate calibration.
  • Miscellaneous
    • Low Radio Frequency Interference (as compared with Arduino and Raspberry Pi 3) - Easier to hear selected satellites.
    • DC reverse polarity protection - Setup at night with no more smoke and tears.
    • Low power consumption - Runs 8 hours on 2Ah battery.
    • Stall resistant motors and gearboxes with all metal gears - Safer operation with longer lasting gearboxes and no stripped gears.
  • Enclosure Size: 125x85x55mm (5.0x3.3x2.2inch)
  • Operating voltage (typical): 12-15.0VDC
  • Operating current (typical): 300mA
  • Startup time (max seconds): 60
  • Antenna rotation speed (max): 0.6 RPM azimuth and elevation
  • Supported radios: Yaesu FT-817/818/857/897
  • Supported USB CAT Cables: Yaesu CT-62 (Genuine FTDI Chip)
  • Sensor cable length: 1m
  • Power cable length: 1m
Please read the following very carefully. We accept no responsibility or liability for the following:
  • This is a DIY project for the experience builder. We are not responsible for your time, costs, tools, availability or substitution of parts.
  • Beware of moving parts - Unit may move at any time without warning. Do not stand or permit anyone to stand in the vicinity of the operating unit.
  • Beware of eye hazard - Moving satellite antennas are prickly. Eye protection is recommended.
  • Beware of pinch hazard - Keep fingers away from moving parts.
  • Beware of electromagnetic radiation hazard - Do not use with high power transmitters. Recommend 10 Watts maximum.
  • Beware of electrocution hazard - Do not use near power lines.
  • Beware of lightning hazard - Do not use in thunderstorms, rainy or windy conditions.
  • Beware of fire hazard - The unit has no built-in over-voltage or over-current protection.
  • Not suitable for unattended operation.
  • Not suitable for fixed or permanent outdoor operation.
  • Automatically connects to the Internet: Adult permission and charges may apply.
  • Constant adult supervision of the operation is required to prevent injury, especially around children.
  • Constant adult supervision of the operation is required to prevent damage to the unit, anything attached to the unit or anything in the vicinity of the unit.
  • Constant adult supervision of the operation of radio transmitters is required at all times. You must check your licence conditions and operating frequency.
  • Antenna, tripod, lift arm, mountings, cables or anything in the vicinity of the unit may be damaged under normal operation or due to software malfunction.
  • The motors a light-duty: Do not force them. Avoid striping the metal gears.
  • Installation of a safety DC cut-off switch is recommended.
  • Suitable for rotating only a single, small directional antenna (e.g. A handheld, dual-band, Yagi antenna such as an Arrow antenna) using a counterbalanced lift arm.
  • Currently only suitable for controlling the Yaesu FT-817, All-band, All-mode, radio transceiver at this time. Others types to be advised.
  • Performance may become sluggish if more than ten (10) satellites are actively selected for tracking.
  • Unit will oscillate unless solidly mounted only on a rigid stand, such as a heavy-duty (speaker) tripod.
  • Any formatting or data errors in the configuration files will stop the operation of the unit. Always keep a backup of the working configuration files.
  • Oscillates between start azimuth points if predicted passes have the same AOS time in minutes
  • Displays predicted passes even with zero degrees maximum elevation
  • Web pages are static: Track button must be re-pressed to refresh correct tracking status
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