Category: Antennas

DragonBridge: Streaming IQ Data Over 802.11ah HaLow via Two Relay Drones

Aaron, creator of DragonOS, has uploaded a video on his YouTube channel showing him testing out long-range communications via 802.11ah Wireless Networking and a T-HaLow bridge on two drones. 802.11ah (aka HaLow) is a WiFi protocol designed for long range IoT communications of up to 1 km (without obstructions).

In the video, Aaron attempts to stream IQ data with SDR++ over 802.11ah HaLow from a Pi + KrakenSDR operating over 1.6km away. The communication is established via two drones in the air that act as a relay bridge between the two ground stations. Although there are issues with keeping the connection stable, these experiments serve as a great first test of this capability.

Join me on an exciting month long+ journey as I push the boundaries of wireless communication using the Lilygo T-HaLow 802.11ah devices in bridge mode! In this video, I demonstrate how I successfully established an SSH connection from my laptop, across six T-HaLow units—some mounted on two drones and others on the ground—to a Raspberry Pi ground station equipped with DragonOS pi64 and a KrakenSDR.

What You'll See:

Innovative Network Setup: I configured three pairs of T-HaLow units, each pair consisting of an access point and a client. The first pair connected my laptop to the first drone. On each drone, I bridged two T-HaLow units via Ethernet, effectively creating a relay system. The second pair connected the two drones, and the third pair linked the second drone to the ground station Raspberry Pi.

Successful Long-Distance Communication: By the third attempt, I achieved a stable ping across the entire bridge and streamed IQ data from the SDR++ server on the Raspberry Pi to the SDR++ client on my laptop—over a distance of 1.6 km between drones!

Challenges and Triumphs: Experience the hurdles I faced, from connectivity issues to environmental obstacles, and how perseverance led to a successful connection.

Stunning Aerial Footage: Enjoy breathtaking drone shots that not only showcase the technology but also add a visual treat to the technical journey.

Why This Matters:

This project highlights the potential of increasing the standoff distance between equipment using 802.11ah technology, also known as Wi-Fi HaLow. Operating in the sub-1 GHz unlicensed bands, 802.11ah offers extended range and improved propagation through obstacles compared to traditional Wi-Fi frequencies. It's designed for low-power, long-range connectivity with lower power consumption—ideal for IoT applications, remote deployments, and innovative projects like this DragonBridge.

Equipment Used:

Building the DragonBridge: Long-Range 802.11ah Wireless Networking with Drones and T-HaLow Devices

Receiving Starlink Signals with an RTL-SDR and Ku-Band LNB

Over on YouTube, dereksgc has uploaded a new video showing how to receive signals from Starlink satellites using an RTL-SDR and a standard Ku band LNB. Note that this setup simply receives the raw signals, and it does not allow you to connect to the Starlink service.  

In the video, dereksgc first introduces Starlink satellites and explains what signals they transmit, referencing a paper on the structure of the Starlink Ku-band downlink by researchers at the University of Texas. He notes that the signals are strong enough that a single LNB without a dish is sufficient for receiving them. An LNB is a feedhorn antenna, low-noise amplifier, and downconverter all-in-one. It converts the ~10.950 GHz Ku band signal of the Starlink satellites down to a frequency that the RTL-SDR can receive.

In the rest of the video, he shows a timelapse of signals being received. The signal's doppler shift can be seen and heard as the satellite passes over.

Receiving Starlink signals with RTL-SDR

Paper on Building a Low Cost RTL-SDR Based Hydrogen Line Radio Telescope

Back in 2020, we posted a tutorial on how to set up a low-cost Hydrogen Line radio telescope using an RTL-SDR, LNA, and WiFi grid antenna. Since then we have seen similar setups successfully replicated in the community many times.

In a recent Hackaday post, we discovered a paper by Jack Phelps who has written an in-depth technical and scientific description of his attempt at Hydrogen line radio astronomy with similar equipment. His paper goes into deeper scientific explanations and describes the experiment and hardware setup in detail including some signal processing, observation, and calibration equations that might be useful for those looking to understand the science more deeply. 

Jack Phelps Radio Astronomy Setup and some Results
Jack Phelps Radio Astronomy Setup and some Results

Building an “HF Helper” for Improving RTL-SDR HF Reception

Over on YouTube Amateur Radio VK3YE has uploaded a video showing his 'HF Helper' project. The HF Helper is a tunable HF filter and attenuator that helps improve HF reception when in the presence of strong overloading signals. VK3YE writes:

Using an RTL-SDR.COM dongle (genuine model V4) and a computer with SDR Sharp you can get quite good reception of HF signals. However reception can sometimes be spoiled by overload from signals on or away from the desired reception frequency. The 'HF Helper' presented here can reduce these problems. And you can use it in conjunction with a QRP transmitter to form a simple transmitting station.

RTL SDR HF Helper improves reception

Also as a bonus, in a related video VK3YE also shows the RTL-SDR Blog V4 being used on SDR Touch on an Android phone for portable HF, VHF and UHF reception.

Hear HF VHF UHF on an Android phone

Project H Line 3D: YouTube Talk

Last week we posted about Alex Petit Jr's 'Project H Line 3D' which is a collection of documents and programs designed to be a beginner's guide to antenna fabrication, reception, recording, software processing, and graphic display of the 21 cm Hydrogen line. The project makes use of an RTL-SDR and LNA as the radio front end.

This week Alex gave an online talk to the Society of Amateur Radio Astronomers (SARA) discussing the project and giving an overview.

Project H Line 3D' is a collection of documents and programs designed to be a beginner's guide to antenna fabrication, reception, recording, software processing, and graphic display of the 21 cm Hydrogen line. The project makes use of an RTL-SDR and LNA as the radio front end.

The Hydrogen Line is an observable increase in RF power at 1420.MHz that is created by natural hydrogen atoms. The Hydrogen line is most easily detected by pointing a directional antenna toward the Milky Way where neutral hydrogen is abundant. Properties of the hydrogen line curve such as its shape and Doppler shift can be used to measure the shape and properties of our galaxy.

Alex's project H Line build is designed to be inexpensive and easy for students to build and set up for drift scans which involve pointing the antenna towards the sky and letting the Earth's rotation drift the Milky Way into and through the view of the antenna.

The project includes a design for a 13-element circular patch feed Yagi that can be built using common materials available from a hardware store. The 13-element Yagi results in about 15dBi gain and a 30-degree 3dB bandwidth.

The software portion of the instructions uses the SDR# IF Average plugin, and uses that to record log files every few minutes. The log files are then converted by an included Java program by Jamison Adcock into a logarithmic dB scale and a format compatible with Rinearn 2D and 3D graphics packages.

Alex Pettit & Jamison Adcock: H Line 3D project

Receiving Weather Images from NOAA Weather Satellites with an RTL-SDR Blog V4 and Multipurpose Dipole Antenna Kit

Over on YouTube Baltic Lab has uploaded a video showing how he was able to successfully use an RTL-SDR Blog V4 and the included multipurpose dipole antenna kit to receive images from polar-orbiting NOAA weather satellites.

In the video, Baltic Lab shows how to orient the dipole antenna in a "V-Dipole" shape which optimizes it for receiving from satellites. He also shows how to use a VNA to confirm that the telescopic elements on the dipole are extended to the correct length, noting that he was able to achieve a VSWR of less than 1.2 between the target frequencies of 135 to 138.1 MHz, with a near perfect match at 136.5 MHz.

He then demonstrates receiving the NOAA APT signals with his laptop, and successfully recovering the weather satellite image.

Receive Live Weather Images from Space at Home

Tech Minds: Testing an Inmarsat L-Band Helix for Offset Satellite Dishes

In his latest video, Matt from the TechMinds YouTube channel tests out an LHCP L-band helix feed designed for receiving Inmarsat satellites. Matt pairs the feed with an 85cm satellite dish, an L-band LNA, and an Airspy Mini.

The L-band helix feed comes from a small German engineering company called nolle.engineering. The feed is priced at 94.70 Euros (incl. VAT) (~$102 USD), plus shipping costs. It is a passive antenna so it needs to be combined with an LNA to be usable with a typical SDR.

In the video Matt shows that the reception with the LHCP helix + dish setup is better than expected. He also compares it to a previous test he did with a longer RHCP helix antenna also produced by nolle.engineering. The RHCP antenna is used to be used without a dish, however, as expected the SNR is less than the dish + small LHCP feed setup. Matt then shows some Inmarsat signals being decoded including STD-C and Aero voice.

This L Band Helix Antenna Gives Amazing Performance

Antennas Explained: Finding the Best Antenna for HackRF, RTL-SDR and Other Receivers

Over on YouTube sn0ren has uploaded a well produced video to help beginners to the radio hobby understand antennas. The video explains how antennas work in theory, and how to choose the best antenna for your SDR and application through calculations and use of a Nano VNA.

There is an essential gadget that you will want to get, to get the best antenna performance. But first we need to cover a bit of antenna theory, before we can answer the question of what antenna that is the best one for your HackRF Portapack, or Flipper Zero SubGHZ module, or Meshtastic, Quansheng UV-K5, RTLSDR or other radio devices. This video is covering the bare minimum basics of antenna theory for beginners into the radio hobby.

The best antenna for HackRF Portapack (and Flipper Zero, Meshtastic, Quansheng, RTLSDR, etc.)