Tagged: rtl2832u

Amateur Radio Direction Finding With a KrakenSDR: AREG Presentation

Over on YouTube, we've seen a talk by Mark Jessop that may be interesting to some readers, as it covers Amateur Radio Direction Finding / Fox Hunting with the KrakenSDR, as well as various other radio tools. If you are unaware, KrakenSDR is our 5-channel coherent RTL-SDR based software defined radio system, designed for coherent applications like radio direction finding.

In the talk, Mark explains the amateur radio fox hunting sport, which involves the organizer hiding a transmitter somewhere in a defined area and having participants search for it using just its radio emissions. He goes on to show the different types of antennas, radio systems and vehicle setups participants used.

Mark further explains that on his particular vehicle, he uses a KrakenSDR as the primary receive system. He explains how the KrakenSDR works, how he integrated it into this vehicle and the custom software and LED display that he is using with it. 

ARDF at Mt Gambier - by Mark VK5QI and Grant VK5GR - AREG September 2025 Presentation

A Small 11.2 GHz Motorized Radio Telescope with TV Dish and RTL-SDR

Thank you to Kaustav Bhattacharjee for writing in and submitting to us his project, where he created a small 11.2 GHz motorized radio telescope with a TV dish and an RTL-SDR. A full description of Kaustav's work can be found in a white paper he wrote on behalf of the Department of Physics at the Indian Institute of Technology Roorkee. In summary he writes:

Briefly put, the hardware Setup comprises a 66 cm parabolic dish, a standard Ku-band LNB with bias tee power injection as the frontend, an RTL-SDR V3 tuned to 1.45 GHz (due to downconversion) as the receiver and a Raspberry Pi 5 handling SDR data (via GNU radio) and stepper motor control (using GPIO pins). A heatmap of the southern sky at 0.9° resolution, showing a belt of geostationary satellites, is the primary result of interest!

We also want to point out that his rotor setup involves several 3D printed gears driven by two NEMA17 stepper motors. However, Kaustav notes that the long term resolution is limited due to cumulative backlash errors from the open-loop control scheme.

Kaustav's 11.2 GHz RTL-SDR Radio Telescope
Kaustav's 11.2 GHz RTL-SDR Radio Telescope
Geostationary satellites visualized with the radio telescope
Geostationary satellites visualized with the radio telescope

Creating a Spectrum Analyzer with Zoom Capability with an RTL-SDR in GNU Radio

Thank you to Paul Maine "The SDR Guy" for submitting his latest video showing how to create a simple spectrum analyzer with zoom capability, using an RTL-SDR and GNU Radio. Paul writes:

Zoom capabilities are discussed in the 3rd edition of Richard G Lyons “Understanding Digital Signal Processing” book. This is a novel approach when compared to other YouTube videos about creating a Simple Spectrum Analyzer with an RTL-SDR.

Additionally, in the video, Paul explains what a spectrum analyzer is and what it's used for, as well as explaining the use of attenuators and discone antennas. In the video, Paul uses an RTL-SDR Blog V4, but has mentioned that an RTL-SDR Blog V3 would work well too.

E19 Create a Spectrum Analyzer with Zoom Capabilities

Reverse Engineering the RF Communications on a 27 MHz RC Toy with an RTL-SDR and GNU Radio

On his blog, Jacob has recently uploaded an interesting post showing how he used an RTL-SDR to reverse-engineer the 27 MHz RF communications protocol used by his kids' RC toy truck.

To reverse engineer the protocol, Jacob used GNU Radio to visualize and demodulate the signal. He discovered that it was modulated via Amplitude Shift Keying (ASK), and viewing the waveform in a time-domain plot confirmed the on-off nature of the signal. Next, using symbol sync and thresholding blocks, he generated a bit pattern, which was then processed using Python.

Reverse Engineering the RC Toy Truck 27 MHz Signal
Reverse Engineering the RC Toy Truck 27 MHz Signal

rtl_tcp_echo: Record and Replay IQ Streams with a Transparent rtl_tcp Proxy

Thank you to Sarah Rose Giddings for submitting news about the release of one of her latest software programs called "rtl_tcp_echo". This “man-in-the-middle” application enables you to simultaneously monitor and record signals of interest, then replay the captured IQ data at a later time using software compatible with rtl_tcp.

The software is compatible with Linux, and Sarah notes that a Windows build will be available soon.

RTL_TCP_ECHO is a Go application that acts as a proxy between an rtl_tcp server and its client. It transparently passes control commands (such as frequency, gain, and sample rate), forwards IQ data, and records the IQ stream to a file. Later, you can run the application in playback mode, serving the recorded IQ data as a fake rtl_tcp server—allowing SDR software to connect and replay the IQ stream.

Features

  • Proxy Mode:
    Forwards all rtl_tcp commands (including frequency and gain) and IQ data between client and server. Simultaneously records IQ data to a file.

  • Playback Mode:
    Serves a previously recorded IQ file as an rtl_tcp-compatible server for SDR software to connect and decode.

  • Transparent Command Handling:
    All client commands (frequency, gain, sample rate, etc.) are passed through with optional logging.

  • Simple Configuration:
    Easily specify listen/forward addresses and recording/playback file paths via command-line flags.
rtl_tcp_echo usage
rtl_tcp_echo usage

An Introduction to SDR’s and GNU Radio using an RTL-SDR

Thank you to Paul Maine for submitting his latest YouTube video titled "Introduction to SDRs and GNU Radio Using an RTL-SDR". The video introduces the RTL-SDR and GNU Radio, and then proceeds to demonstrate how to build a simple FM receiver using GNU Radio. Paul goes on to explain some further concepts, such as sampling, aliasing, interpolation, decimation, upsampling, and finally shows a few more example receivers built in GNU Radio.

E18 Introuction to SDR's and GNU Radio Using an RTL-SDR

EU Ham Radio Shops Suspend Shipments to the United States

With the recent changes to US import policy, many shops in the EU, including ham radio shops, have begun suspending shipments to the United States. This is the result of both a widespread suspension of shipments to the US by most EU mail carriers and the ongoing unpredictability of the situation.

One French reseller of our products has written in to our blog, and wanted to explain the reason for their decision to suspend shipments to the US. We believe that other ham radio shops in the EU may also be in a similar position.

To our US Amateur Radio Clients and Community

Because of the recent 15% tariff increase on products imported from the European Union, the suspension of several carrier services to the US, and the growing complexity of the US import system, our online shop Passion-Radio.com must suspend all shipments to the United States until further notice.

In particular, La Poste, the French national postal operator, suspended parcel shipments to the United States as of August 25, 2025 (1), removing one of the main EU–US postal channels. At the same time, UPS announced that starting September 8, 2025, an additional international processing fee will apply to all import shipments, regardless of origin.

There has also been some misunderstanding regarding customs procedures. When parcels arrive in the United States, the buyer must settle not only the 15% customs duty, but also the service fee charged by the carrier for filing customs declarations and advancing duties to US Customs. These charges are billed locally at delivery and remain outside the seller’s control. Import duties and tariffs are always the responsibility of the buyer, not the seller.

"Unfortunately, with constant changes in tariffs, rates, and carrier processes, we cannot guarantee fair, efficient, and transparent shipping conditions," said David, F1JXQ, Director of Passion Radio. "Our goal is to resume shipments to the US as soon as a reliable and cost-effective solution is available for everyone."

Meanwhile, our collaboration with five US-based suppliers continues without disruption, as the European Union has not imposed any retaliatory tariffs or reciprocal 15% import duties on products arriving from the United States.

Updates will be communicated through our shop: https://www.passion-radio.com/store/hamradio-us-tariff-43 and our social channels.

To all our US friends on the bands: we thank you for your understanding and support, and we look forward to resuming deliveries as soon as possible.

They go on to explain an example:

Practical tariffs impact on an item €50

Before tariffs (without 15%, rate €1 = $1.12 April 2025 rate)

Conversion: €50 × 1.12= $56.00*

Total payable ≈ $56.00

After tariffs (with 15%, rate €1 = $1.16 August 2025 rate)

Conversion: €50 × 1.16 = $58.00*

Customs duty 15%: $58.00 × 0.15 = $8.70

Carrier fees (on average, import processing): $15.00

Total payable ≈ 58.00 + 8.70 + 15.00 = $81.70

Total surcharge ≈ +$25.70 (~+45.89% increase compared to $56.00, before tariff tax)

* Not calculated, fees that may apply when converting Euro € <> US $.

FAQ

• Q1: Who pays import duties and tariffs when ordering from Europe?

By law, the US buyer must pay all customs duties, tariffs, and fees when importing goods from Europe. These charges are not paid by the seller.

• Q2: Why do carriers charge extra fees?

Carriers like UPS, FedEx, or DHL must submit customs declarations and advance duties to US Customs. For this, they bill a brokerage or processing fee directly to the buyer.

Sources :

(1) https://www.lemonde.fr/economie/article/2025/08/22/la-poste-suspend-l-envoi-de-colis-vers-les-etats-unis_6633516_3234.html

WOW@Home: A Global Network of RTL-SDR Based Radio Telescopes Looking for Alien Technosignatures

The Wow! signal is a famous, strong, and unexplained radio signal detected in 1977 by the Big Ear radio telescope in Ohio, lasting 72 seconds and appearing to originate from the constellation Sagittarius. Its origin remains unknown, with some speculating that it could be an extraterrestrial technosignature. Upon reviewing the signal data, Astronomer Jerry R. Ehman discovered the powerful signal burst in the readout and wrote a large "Wow!" next to it, unintentionally coining the name.

Wow@Home is a new project that aims to coordinate a network of small radio telescopes globally, in the hopes of increasing our chances of detecting interesting astrophysical and technosignature events, such as the Wow! event.

A network of small radio telescopes offers several distinct advantages compared to large professional observatories. These systems are low-cost and can operate autonomously around the clock, making them ideal for continuous monitoring of transient events or long-duration signals that professional telescopes cannot commit to observing full-time.

Their geographic distribution enables global sky coverage and coordinated observations across different time zones, which is especially valuable for validating repeating or time-variable signals. Coincidence detection across multiple stations helps reject local radio frequency interference (RFI), increasing confidence in true astrophysical or technosignature transient events.

These networks are also highly scalable, resilient to single-point failures, and capable of rapid response to external alerts. Furthermore, they are cost-effective, engaging, and accessible, ideal for education, citizen science, and expanding participation in radio astronomy.

However, these systems also come with notable limitations when compared to professional telescopes. They have significantly lower sensitivity, limiting their ability to detect faint or distant sources. Their angular resolution is poor due to smaller dish sizes and wide beamwidths, making precise source localization difficult.

Calibration can be inconsistent across stations, and frequency stability or dynamic range may not match the performance of professional-grade equipment. Additionally, without standardized equipment and protocols, data quality and interoperability can vary across the network.

Despite these constraints, when thoughtfully coordinated, such networks can provide valuable complementary observations to professional facilities.

The team note that the Wow! signal was strong enough that it could have been detected by a small home radio telescope. They go on to make the case that we could be missing out on detecting many compelling signals simply because radio telescopes aren't watching every part of the sky simultaneously. 

The project will monitor the Hydrogen Line frequency for interesting signals. Currently, the team is using a WiFi grid dish and an external LNA as the radio telescope hardware, but they also aim to evaluate our Discovery Dish with H-Line feed.

Wow@Home Typical Radio Telescope Hardware
Wow@Home Typical Radio Telescope Hardware