DIY Satellite Tracker

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!

Related link:
Mini Satellite Antenna Rotator (SARCNET)
DIY Rotator Controller

Night Sky in Focus
Astronomy and Amateur Radio
© Anthony Urbano (Manila, Philippines

DIY Arduino TNC

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.

Related links:
DIY Moxon-Yagi Satellite Antenna
Portable Satellite Radio Setup

Night Sky in Focus
Astronomy and Amateur Radio
© Anthony Urbano (Manila, Philippines

PSAT2 Satellite SSTV Images

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.

Related links:
DIY Moxon-Yagi Satellite Antenna
Portable Satellite Radio Setup

Night Sky in Focus
Astronomy and Amateur Radio
© Anthony Urbano (Manila, Philippines

DIY Satellite Antenna DU1AU

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.

Related links:
Portable Satellite Radio Setup
DIY Satellite Radio Wins Go-Kit Contest

Night Sky in Focus
Astronomy and Amateur Radio
© Anthony Urbano (Manila, Philippines)

DIY Satellite Radio Wins Go-Kit Contest

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.

Related links:
DIY Satellite Antenna
Portable Satellite Radio Setup
Amateur Radio on the International Space Station (ISS)

Night Sky in Focus
Astronomy and Amateur Radio
© Anthony Urbano (Manila, Philippines)

Talk on Amateur Radio Satellites

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.

Related link:
4th UP RI-NOAH Talk on Disaster Resiliency

Night Sky in Focus
Astronomy and Amateur Radio
© Anthony Urbano (Manila, Philippines)

SSTV Images August 3-4, 2019

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.

Related links:
Satellite Communications
My Satellite Antenna

Night Sky in Focus
Astronomy and Amateur Radio
© Anthony Urbano (Manila, Philippines)

Satellite Demo with the Philippine Navy

I was invited to conduct a live satellite demo at the Philippine Navy as part of the exit presentation of DOST-Balik-Scientist CDR Leo Almazan USN (ret) 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).

Naval Sea Systems Command
We used DIWATA2 satellite to bounce a signal from our location in Cavite, to other radio operators in Pangasinan, Cotabato, and as far away as Japan. Copyright: Naval Sea Systems Command, Philippine Navy

For this demo,  I used a home-brew portable satellite radio setup and a DIY satellite antenna.

To view all posts on amateur radio, click here.
Related link: Satellite Demo at a local Hamfest

Night Sky in Focus
Astronomy and Amateur Radio
© Anthony Urbano (Manila, Philippines)

Portable Satellite Radio Setup

The ability to operate off-the-grid is a huge advantage when hunting satellites. Coupled with a portable antenna, this battery-operated radio setup can be easily carried to any remote DX location while requiring only very minimal prep time (5 minutes). Simply connect a satellite antenna, turn the radio on,  select the pre-programmed uplink and downlink frequencies, and you are ready to make contact!

The portable satellite radio setup consists of the following:

1. Kenwood TMV71A full-duplex VHF-UHF radio with microphone
2. 12V 8AH lead-acid battery pack with volt meter
3. Sony recorder
4. Headset
5. Other accessories (not shown) such as SWR meter, patch cable, compass, flashlight, notebook, pencil, etc.

Satellite Go-Bag (3).jpg
Everything fits in a small waterproof camera bag, with room to spare for some accessories.

This setup has been used recently in a satellite demo at a local hamfest. Since only 5 watts of power is needed to access the FM satellites, this setup lasts for one week of use (about 50 satellite contacts) in a single charge, perfect for DX-peditions!

Related links:
DIY Satellite Radio Wins Go-Kit Contest

Night Sky in Focus
Astronomy and Amateur Radio
© Anthony Urbano (Manila, Philippines)

SSTV Images Received February 15-17, 2019

Here are the Slow Scan Television (SSTV) images I’ve received from the International Space Station (ISS) from February 15-17, 2019, using a Yaesu FT60 hand-held tranceiver and a smartphone with Robot 36 app as decoder. The audio output of the radio is tapped directly to the microphone input of the smartphone for improved signal decoding.

To lean how to receive SSTV images from the ISS, head directly to Receiving Transmissions from the International Space Station.

To learn more about my progress in amateur radio, click here.
Related link: Amateur Radio

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© Anthony Urbano (Manila, Philippines)