I’ve recently finished building and testing a simple and low-cost DIY satellite tracker based on the SARCNET satellite tracker project by VK3FOWL and VK3YSP.
The SARCNET page mentions that at least 737 hams (as of May 2020) reported to have successfully built a similar tracker. You, too, can build one! Imagine having this tracker on your next satellite demo and local hamvention exhibit!
It works with an app such as Gpredict and tracks the satellite automatically!
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 du1au@nightskyinfocus.com. To learn more about satellite communications, click here.
I’ve conducted a satellite communications demo with the group Amateur Radio Communications and Emergency Response Team (ARCERT) on February 8, 2020, in Marikina City. The satellite AO-91 was used in this demo, accessed using only a two-way radio and a DIY antenna.
Special thanks to stations who participated in the demo: DV2JB (Dagupan), JS6DRQ (Japan), DW9ILX (Davao), DV7DYH (Dumaguete), and 4G1AGI (Laguna).
To view all posts on amateur radio satellite communications, click here. To view all posts on amateur radio, click here.
I have built an improvised trainer that uses a guitar tuner’s tone generator feature to generate the tone needed to operate a Morse code key. The tone generator (guitar tuner) and the power supply (two AA batteries) are tightly placed in a small pocket-sized enclosure with a straight key mounted at the top, making the Morse code trainer a bring-anywhere ultra portable tool for code practice.
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.
On October 28, 2019, I was invited by the UP Resilience Institute-NOAH to deliver a talk about amateur radio satellites.
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.
