Thank you to Nagy István for writing in and sharing with us his video showing how he uses a home-made backfire helix antenna and the JAERO software to receive and decode Inmarsat Aero at 1545 MHz. AERO messages are a form of satellite ACARS, typically containing short messages from aircraft, and some channels also support digital voice communications.
The backfire helix is an antenna design that consists of a helically wound wire, typically wound around a 3D-printed frame, attached to a large backplane. Recently, a similar design called a 'heliocone' has become popular for use with 1.7 GHz polar orbiting satellites.
In the video, Nagy shows two designs, one of his own and the other by Digitalelektro, and the good SNR that he's achieved with them in JAERO.
Inmarsat Aero 1545Mhz decoding with Backfire helix / JAERO software
Thank you to Alexandre Gellibert for writing in and sharing his new Android App, "SDR ProTrack." SDR ProTrack is a radio direction-finding app that uses an RTL-SDR and directional antenna to determine a bearing towards a transmitter.
Interestingly, Alexandre notes that this app was initially developed to track Asian hornets, a bee-killing pest. With hornet tracking, a miniature RF transmitter is attached to a caught hornet, and the hornet brings it back to the nest. RF tracking techniques can then be used to find the nest.
It's possible to determine the bearing toward a transmitter by using a receiver such as an RTL-SDR paired with a directional antenna like a Yagi. Directional antennas have high sensitivity in one primary direction and significantly lower sensitivity in all others. By rotating the antenna until the strongest signal is identified, you can establish the precise bearing angle. Typically, following this bearing will guide you directly toward the signal's origin.
Alexandre wrote in an email to us the following:
Just to let you know we just launched a new Android app compatible with RTL-SDR dongles (though mostly tested on RTL-SDR v4).
App is free to use. Advanced features (like Compass to point the signal potential source) are for premium users.
It's plug and play, easy to use, much more user friendly than SDR++.
Any feedback is really appreciated :)
If you want to know more about the project or the 2 developers behind it (we develop it in France to be able to track asian hornets that kill all the bees), please feel free to contact us.
And the Android page describes SDR ProTrack in the following way:
Unlock the power of radio tracking with SDR ProTrack! Transform your Android smartphone into a signal-tracking powerhouse using an RTL-SDR dongle and a directional antenna. Affordable, versatile, and perfect for enthusiasts, researchers, pros or anyone tracking signals—like Asian hornets or wildlife.
★ Key Features ★
• Automatic RTL-SDR dongle recognition and connection (free) • Spectrum Visualization (Free): View signal shapes in the frequency domain effortlessly. • Compass (Premium): Pinpoint the strongest signal direction with precision. • Signal Strength Display (Premium): Monitor signal power with an intuitive interface. • Custom Settings (Premium): Adjust bitrate, sample rate, and frequency sensitivity to your liking.
★ Requirements ★
• Requires an external RTL-SDR device. • Check compatibility: https://osmocom.org/projects/rtl-sdr/wiki
Need an RTL-SDR dongle, emitters, receptors, or antennas? Visit our website: https://www.intuite.fr/en_GB/pricing
★ About Us ★
Intuite is a company specialized in locating Asian hornet nests. We developed SDR ProTrack to provide a robust, cost-effective solution for radio signal tracking, combining innovative technology with our expertise in signal detection.
★ Open Source Community ★
Join our mission to advance radio tracking! Our open-source library, RTL-SDR Bridge Android Lib, powers SDR Pro Track. Contribute to development, report issues, or explore the code at https://github.com/alexandreGellibert/RTL-SDR-Bridge-Android-Lib. Support our work and help shape the future of signal tracking!
Download SDR ProTrack today and start tracking signals like a pro!
The talk focuses on using SDR hardware such as the RX888, RTL-SDR, and Airspy devices combined with directional antennas for radio direction finding. Interestingly, they also discuss using ultrasonic microphones to find power line noise from bad transformers or insulators. The talk also focuses on ensuring that your SDRs receive real signals and what noise might look like on the spectrum.
This talk provides a comprehensive guide to identifying and locating radio transmitters. Learn about practical techniques, common tools, and methodologies from decades of combined experience finding, squashing, and mitigating against radio frequency interference.
Supercon 2024: Justin McAllister and Nick Foster - How to Track Down Radio Transmissions
An antenna's radiation pattern tells us how it radiates or receives electromagnetic energy in different directions, indicating the strength, directionality, and coverage area of its signals. These days, this is easy to simulate on a PC. However, getting real-world results can still be essential to ensure an antenna is constructed well. For commercial antennas, real-world testing is typically done in an RF anechoic chamber.
In the post, List tests an HB9CV two-element 144MHz Yagi antenna. As expected, the resulting polar plot from the measurements indicates that the HB9CV is a directional antenna.
We've seen a similar setup in the past, as shown in this post, where a NanoVNA was used to measure the antenna power.
In a recent video on the saveitforparts channel Gabe shows how he used a DIY radio telescope to take a video of geosynchronous TV satellites. The system works by using a motorized dish to scan the sky at Ku-band frequencies. An SDR is used to receive the signal strength at each dish position, and this data is used to create a heatmap image.
Each scan takes an hour to scan the sky, but by running a scan every hour, Gabe is able to create a video of the geosynchronous satellites wobbling. While still mostly fixed at one position in the sky, unlike geostationary satellites, geosynchronous satellites can appear to move in a figure-eight pattern from the ground, and this wobbly movement is apparent from Gabe's video.
The video also shows the sun passing by every 24 hours as the sun emits some RF energy in the Ku-band, as well as brief blips from Starlink satellites. The video also shows the effect of rain fade, as Gabe shows how the heatmap power was attenuated during poor weather.
Videos Of Satellites In Space Made With DIY Radio Telescope
Thank you to Marco Cardelli (IZ5IOW) who recently wrote in and shared with us his design for mounting a YouLoop antenna indoors, which he uses with his Airspy HF+ Discovery SDR receiver.
Marco's build involves an MDF wooden base measuring 15cm x 15cm, supporting a vertical mast made from a 70cm long, 25mm diameter PVC pipe. The mast is secured to the wooden base using a repurposed metal bracket and cable ties.
Additionally, Marco constructed square loop enclosure out of 20mm diameter PVC pipe for containing his HFDY active loop, measuring 60cm per side. The HFDY is an active loop variant of the YouLoop, available on sites like Aliexpress.
Marco's YouLoop stand, and the inside of the HFDY active loop.
Typically, a satellite dish is used to receive Elektro L3. As an example, our 70cm diameter Discovery Dish with linear feed can do this easily, and achieve an SNR of about 5-6 dB. However, as Meti shows, it is possible to receive this satellite even without a dish, and as he shows, an SNR of 1.5 dB is sufficient for decoding a perfect image.
Meti's antenna is an 11-turn RHCP helix made of copper wire, with a 17 x 17cm ground plane. In his post, he also notes a few interesting findings, noting that the height of the antenna off the ground is critical, rotating the helix can help, interference from cell towers can cause issues, and bending the corners of the ground plane can help.
In the rest of the post, Meti also shows how well the helix antenna works at receiving weather satellite signals from polar orbiting L-Band satellites like Meteor M2-3.
NOAA GOES satellites are a popular way to receive beautiful full-disk weather images of the Earth using an RTL-SDR, antenna hardware such as the Discovery Dish, and software such as SatDump. The GOES-EAST satellite covers North and South America and was provided by GOES-16 until April 7th.
Over the past few months, NOAA has been moving the GOES-16 satellite into a storage orbit and the newer GOES-19 satellite, which was launched in June 2024, into the GOES-EAST position. Recently, on 7 April 2025, this transition was completed, and the GOES-16 was turned off, and the GOES-19 signal was activated.
For SatDump users, no configuration changes should be necessary to receive signals from GOES-19. However, Sanchez users will need to update their configuration file.
