The International Space Station (ISS) recently conducted a week-long radio transmissions test by sending encoded signals in Slow Scan Television (SSTV) image transmission format to be decoded by anyone with the proper amateur radio equipment tuned at 145.8 MHz and an SSTV decoder app such as Robot 36. This activity is part of the program Amateur Radio on the International Space Station or ARISS.
SSTV images are sent and decoded line by line, much like how scanners and printers work. To watch a video showing an SSTV image being decoded as the ISS passes above the Philippines on June 25, 2021, 2:30 am, click here.
I have built a DIY satellite tracker based on the SARCNET project. It is a simple Arduino-based motorized azimuth and elevation rotator that uses DC motors to move the antenna, and gets position feedback using an accelerometer and compass.
The tracker receives satellite’s azimuth and elevation info using the tracking software Gpredict. Hamlib is then used to establish a link between the computer and Arduino through USB connection via EasyComm II protocol.
To watch a video of the satellite tracker, click here.
NOAA 15, 18, and 19 are weather satellites that gather and transmit image data real-time at 137 MHz. Any station with the proper radio equipment could receive this signal and decode it using available decoders. NOAA satellites usually make morning and evening passes, and with each pass, an image of the Earth within the satellite’s view can be received.
To receive radio signals from NOAA satellites, I used an AirSpy Mini Software-Defined Radio (SDR) and used GQRX app to run the SDR. I then connected a DIY satellite tracker with antenna to the SDR through its antenna port, but a simpler DIY satellite antenna would also work fine. Using GQRX, and while tuned to the satellite’s signal, I recorded it and saved it in WAV sound format. I then decoded (converted to image) the audio recording with the NOAA-APT decoder. From May 28 to June 1, I received and decoded the morning NOAA satellite passes and compiled them into an animation.
Receiving satellite images using inexpensive home-brewed equipment could be a worthwhile learning activity. To know more about other projects involving satellite communications, click here.
Sixty girl scouts, troop leaders, teachers, and amateur radio enthusiasts attend a webinar on amateur radio satellite operation co-presented by Manila Girl Scout Council Amateur Radio Club (MGSC ARC) and AMSAT Philippines, Inc. on May 29, 2021 via Zoom Cloud Meetings app. Licensed amateur radio satellite operators Anthony Urbano DU1AU and John Kyl Cortez DW9ILX explained how to use satellites to communicate long distances (Philippines to nearby countries) using only a low-cost handheld radio transceiver and an inexpensive home-brewed antenna. Other topics related to receiving real-time satellite images, talking with astronauts aboard the International Space Station (ISS), equipment and licensing requirements, and relevant information on setting up a satellite ground station were discussed during the webinar.
NOAA 18 weather satellite image received on May 25, 2021 with an AirSpy Mini SDR on GQRX SDR app and a DIY satellite antenna. The signal was recorded in WAV sound format and then decoded (converted to image) with the NOAA-APT decoder. NOAA satellites (15, 18, and 19) transmit weather images in APT (Automatic Picture Transmission) format at 137 MHz which may be received using just a VHF antenna, a software-defined radio (SDR), and an APT decoder.
PSAT2 transmits SSTV images at 435.360 MHz (UHF) which may be received using just a DIY Moxon-Yagi satellite antenna, a UHF radio, and a decoder such as Robot 36 running on a smartphone (Android). Here is an image decoded in May 2020, as PSAT2 passes over the Philippines.
SSTV transmission by PSAT2 is active only at daytime. Doppler-effect compensation is necessary to properly receive the transmission. Tune the radio at 435.370 to 435.350 MHz from start to end of the pass. You may decode up to two SSTV images per pass. To watch a a demo video click here.
I’ve recently finished building a satellite traker based on SATNOGS satellite tracker. The automated tracker uses an Arduino to control a pair of stepper motors that move two cross-yagi antennas (VHF and UHF). The Arduino receives satellite’s azimuth and elevation info using the tracking software Gpredict. Hamlib is then used to establish a link between the computer and Arduino through USB connection via EasyComm III protocol.
The tracker uses two A4988 stepper motor driver, and two geared stepper motors. A weatherproof metal box is used as a case, and rubber seals prevent water from entering.
To watch a video about this homebrewed tracker, click here.
On October 28, 2019, I was invited by the UP Resilience Institute-NOAH to deliver a talk about amateur radio satellites. In this talk, I’ve discussed how to access these amateur radio satellites, and explained how to setup a home-brewed satellite phone for reliable communication in times of disaster.
I was invited to conduct a live satellite demo at the Pascual Ledesma Naval Station in Cavite, Philippines. We’ve accessed DIWATA2 (PO-101) and had successful contact with JA6PL (Japan), DV2JHA (Pangasinan), and DU1ELT (Cotabato).
This battery-operated radio setup can be easily carried to any remote location. Connect a satellite antenna, turn the radio on, select the pre-programmed uplink and downlink frequencies, and you are ready to make contact!
I have finished building and testing a DIY Terminal Node Controller (TNC). With a TNC, any radio may encode and decode signals in the Automatic Packet Reporting System (APRS) format. This TNC is based on the home-brewed TNC project by VK3DAN.
The TNC requires a smart phone with APRSdroid connected via bluetooth. It taps directly to a radio through the dedicated audio line-in and line-out ports. I’ve tested this TNC to work with the International Space Station’s (ISS) digipeater at 145.825 MHz, using the digipath: ARISS.
Licensed radio operators from AMSAT Philippines, a local group specializing in satellite communications, worked with STAMINA4SPACE to test the DIWATA2’s Amateur Radio Unit (ARU). The task involves testing the receiving and transmitting capabilities of the satellite’s on-board amateur radio equipment. It also includes determining the kinds of antennas that may be used and how well they work, the clarity of voice communication, and how much power is actually needed to access the satellite.
The testing effort lasted for two months (February to March 2019), requiring operators to track the satellite at it passes over the Philippines using a number of radio equipment and satellite antenna. Below is a video showing a successful contact between stations via the Diwata 2 satellite during its testing phase.
To learn more about amateur radio satellite communications, click here.