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 was built with parts taken from a drill such as gears and bearings, along with a pair of worm drive from a photocopying machine. The total costs of the project is less than 100 USD, antennas included. The tracker uses two A4988 stepper motor driver, and two geared stepper motors. A weatherproof metal ammo box is used as a case, and rubber seals (particularly in the azimuth and elevation shafts) prevent water from entering.
Initial tests showed good tracking accuracy, allowing reliable full-duplex communications with any passing amateur radio or weather satellite.
I have finished building and testing a DIY Terminal Node Controller (TNC). With DIY TNC, it is possible for any radio to 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 running APRSdroid connected via bluetooth. It taps directly to a radio through dedicated audio line-in and line-out ports (or microphone in and speaker out). The PTT is automatically activated as a packet is transmitted. I’ve tested this TNC to work with the International Space Station’s (ISS) digipeater at 145.825 MHz, digipath: ARISS.
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 are some images decoded on May 1 and May 5, 2020, as PSAT2 passes over the Philippines.
SSTV transmission in PSAT2 is only active in daytime. Doppler effect compensation is necessary to properly receive the transmission. Tune your radio from 435.370 MHz down to 435.350 MHz from start to end of the pass. You may decode up to two SSTV images per pass.
This page contains information on how to build a DIY satellite antenna. Two versions of the plan is provided: original and modified.
Moxon-Yagi Version 1: Original Moxon-Yagi Measurements This version of the plan shows the general measurements for a Moxon-Yagi as designed by Ly3LP. Please note that since the performance of the antenna depends on the specific materials used, you may need to make slight adjustments on the measurements in order to tune the antenna to a specific frequency in VHF and UHF.
Moxon-Yagi Version 2: Modified Moxon-Yagi Measurements This version of the plan shows the measurements of the antenna we used during the testing of Diwata 2 (PO-101) satellite, incorporating slight variation in the measurements such as changes in spacing and length of the elements, as it is optimized to work best for PO-101. This antenna also works with any other UHF-VHF satellite.
For details, please read full article below:
A satellite antenna can be made from 3 mm copper or aluminum elements, PVC boom, and some parts you may already have at home. To download the original Moxon-Yagi measurements (highest-resolution), click here.
1. All measurements are in millimeters (mm). 2. Use 3 mm copper or aluminum elements. 3. Adjust the critical gaps for lowest SWR (adjust the 14 mm and 22 mm gaps as needed). 4. Only the VHF elements (Moxon part) are connected to the feedline. The UHF element (325 mm) closest to the feedpoint is the UHF driven element. It is not connected to the feedline, but resonates only when the proper gap is achieved. 5. The feedline connects directly to the radio (no diplexer/duplexer needed). 6. Use translucent plastic insulator from an RG8 cable for the 14 mm Moxon gap 7. Use non-metallic boom (wood or orange PVC pipe). 8. The feedpoint gap is 10 mm. 9. The antenna works with any dual-band UHF-VHF radios
Here’s another version with slightly different dimensions, tuned to have lowest SWR specifically at our local satellite Diwata 2 (PO-101) frequency 145.9 MHz downlink and 437.5 MHz uplink (you may change the UHF and VHF frequencies by adjusting the critical gaps as described above). This antenna has been tested to work also with other satellites such as AO-91, AO-92, SO-50, IO-86, ISS, and PSAT2. Here’s the plan for this antenna, again, with slight variations in measurements as it is optimized for PO-101.
I’ve recently added a PTT switch on the boom, for one-hand operation. Watch the video below to see how the antenna is used in an actual satellite QSO!
Also, the Moxon elements may now be folded, making this antenna far easier to transport. Shown below are 2 versions, one using 3 mm elements, and another using 6 mm elements. The fully-collapsible antenna assembles and disassembles in just a few minutes!
For inquiries, email me at email@example.com. To learn more about satellite communications, click here.
I have just finished building a DIY controller as part of a home-brewed antenna rotator project. The controller allows simple clockwise and counterclockwise movement of the stepper motor using 4 buttons. The motor may be replaced with a larger one depending on the intended load. I have added an optional speaker for audible feedback.
My portable satellite radio setup won 1st place (VHF-UHF category) in this year’s go-kit (portable equipment) contest as part of the 87th anniversary of the Philippine Amateur Radio Association. It is essentially a satellite phone with collapsible antenna which allows communication with anyone, anywhere in the Philippines and neighboring countries such as Japan, Malaysia, China, Korea, Indonesia, India, Sri Lanka, Singapore, Vietnam, Hong Kong, Taiwan, and even Australia, using only a transmit power of 5W.
The go-kit was built in April 2019 to help the STAMINA4SPACE test our country’s first amateur radio satellite DIWATA2.
Amateur radio satellites are orbiting relay stations that enable long distance communications using only a two-way radio and a home-brewed antenna. Unlike other communications systems like the cellular service and the Internet, satellites do not rely on ground-based communications infrastructure. If a locality is hit with a major disaster, damage to infrastructure will render the cellular phones and the Internet unusable, but satellites in space will continue to function. 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.
To view all posts on amateur radio satellite communications, click here.
I’ve received 6 SSTV images from the International Space Station (ISS) from August 3-4, 2019, from my amateur radio station in Bacoor, Cavite, using a DIY antenna and a portable radio. The app Robot 36 was used to decode the SSTV transmissions. For participating in the SSTV event, I was awarded a certificate.
To learn how to receive SSTV images from the ISS, click here.