Tagged: rtl-sdr

Vector Measurements with an RTL-SDR and HackRF Based System

Over the course of 2020 Tomaž Šolc from Avian's Blog has been slowly working on an RTL-SDR based vector network analyzer system. The system currently consists of an ERASync Micro signal generator, a custom time multiplexing board, an RF bridge, an RTL-SDR with E4000 tuner and some custom software.

A vector network analyzer allows the measurement of antenna or coax parameters such as SWR, impedance, phase and loss. It can also be used to characterize and tune filters. In his last post Tomaž copmares his RTL-SDR based system with a NanoVNA-H and shows similar results, confirming that the system is working.

Recently he's also swapped out the RTL-SDR for a HackRF which allows him to make measurements up to 6 GHz. Although he notes that the dynamic range quickly degrades after 3.5 GHz presumably due to connector and phase noise issues.

The entire post chain is a good read to see how he ended up designing the system, and we link to each post below for easier reading:

Homemade Vector Network Analyzer with ERASynth Micro, HackRF, RF Bridge, Custom Time Multiplexor

Frugal Radio: Monitoring En Route Air Traffic Control, Oceanic Clearances, and Company Frequencies

Rob from Frugal Radio has recently uploaded part three in his airband monitoring series. The the last video Rob discussed what communications can be received from the airport. In this weeks video Rob explains how air traffic control is handled over large areas, and also shows examples of what you might hear when an aircraft communicates with it's parent company.

Air Traffic Control Centres provide ATC coverage across most of the globe. This video gives an overview of how you can listen to pilots and Air Traffic Controllers as along their routes.

This video talks about the en route Air Traffic Control systems in the USA (ARTCC managed by the FAA), UK (managed by NATS) and Canada (managed by Nav Canada).

Company frequencies are also covered in this video, along with examples of conversations received at my location in the last few days.

Monitoring En Route Air Traffic Control, Oceanic Clearances, and Company Frequencies

Demonstrating How Speakers Can Become an Unintentional RF Transmitter

Over on YouTube channel Privacy & Tech Tips has uploaded a video showing how he used an RTL-SDR to pick up RF emissions coming from some speakers that were unintentionally acting as wireless microphones. He goes on to show how you can clean up the noisy received audio in Audacity using the noise reduction filter.

I show how electromagnetic emissions from personal devices many times turn our devices into (potential) remote listening + transmitting devices when active (as demonstrated). I discovered my speakers unintentionally transmitting audio (speaker acting as microphone) to a few different frequencies via GQRX recording (computer/Pinetab microphones completely disabled).

There are a few frequencies you can tune into to listen in remotely. This includes listening in to conversations in the room as the speaker also acts as a microphone when playing sound (***tested only on my own devices***).

When the speaker volume is turned down, the signal goes down and the broadcast goes away. When the speaker volume is down, it no longer functions as a remote microphone + transmitter.

We use Audacity to clean up the audio. GQRX is used to record the signals which are filtered on the Pinetab with internal RTL-SDR. Audio processing/noise reduction done running Parrot Linux using Audacity.

We touch on the fact all electronic devices give off their very own unique electromagnetic emissions which can act as device signatures (strength depends on shielding).

Sometimes speaker wire not properly shielded (as is found in most PC's) can act as a radio transmitter antenna without user knowledge. Here I discovered a few frequencies broadcasting the audio live (.25 second delay for SDR modulation).

📡 Laptop Speakers Are Transmitting (Radio) Microphones

Recent Podcasts on Software Defined Radio from Scanner School

Scanner School is an online resource that aims to teach subscribers all about radio scanning. They also run a weekly podcast discussing various topics in the scanning hobby. Recently they've had a bit of a focus on software defined radios, with several of the last podcasts being SDR related.

Episode 170 - SDRplay with Jon Hudson

On today’s episode, host Phil Lichtenberger interviews Jon Hudson, the co-creator of the SDRplay devices. They talk about the evolution of radio scanning software, the advantages of SDRplay and SDRuno, where they think the scanner hobby is headed, and more.

What You Need To Know

Jon Hudson is a co-creator of the SDRplay device. SDRplay manufactures both hardware and software. Before about 20 years ago, processing the radio chain was done exclusively on the hardware. Now computers are powerful enough to support doing most of this work with software. SDRplay was founded in 2014. The RSPDX has multiple antennae, which allows users to switch from one antenna to another quickly and easily. Because SDRplay makes their own software for Windows, they take a lot of time to make sure it works seamlessly out of the box. SDRplay acquired a company called Studio One that manufactured software about five years ago. SDRplay is releasing a scheduler, which will function as an audio recorder for a specific channel at a specific time. An advantage of the scheduler is that it allows users to tune in to certain frequencies at a specified time and then turn it off or move on to something else. All session notes with links to the items we talked about can be found on our website at www.scannerschool.com/session170

170 - SDRplay with Jon Hudson

Episode 169 - SDR++ with Alex Rouma

A cross platform, open source, free SDR software!

In this episode, Phil talks to Alex Rouma, author and creator of SDR++. They discuss how Alex got into SDRs, where SDR++ is now and where he hopes it can go, and how you can contribute to this open source software’s development, whether you’re a programmer or not.

What You Need To Know

SDR++ is free, open-source, cross-platform software for your SDR. Alex got into SDRs after watching a video of someone receiving weather satellites, piquing his interest in radio in general. Alex is currently building SDR++ as general purpose SDR receiver software with more modern functionality like multi-VFO and multi-platform support. SDR++ supports anything Alex has or that companies have sent him, including SDR Play, HackRF, RTLTCP, and more. Alex considers the software still in beta, but thinks he’ll have stable code with the features he wants within 3-4 months. He wants to add audio filtering features and more options for the file source. SDR++ is fully modular so you can add plugins as you need them. Alex aims to make the software as automatic as possible. All session notes with links to the items we talked about can be found on our website at www.scannerschool.com/session169

169 - SDR++ with Alex Rouma

Episode 168 - Using a SDR as Your Scanner

In this episode, Phil talks to listener Greg Weamer about his SDR setup. They get into the history of SDR development, what you can do with an SDR that you can’t do with a hardware-based scanner, and where they think the future of SDRs is heading.

What You Need To Know

Today, Greg does not have a hardware scanner at all, but only a SDR. His area has simulcast problems that the SDR solves. Greg currently uses about 8 RTL-SDR dongles, including 3 on a Raspberry Pi, some on another Raspberry Pi, an old laptop, and more. Greg also uses Trunk Recorder, which is one of the most difficult things he’s ever configured, but he loves that it monitors every voice channel at the same time. RDIO Scanner is a web interface that takes the feeds from the virtual recorders Greg has going and cues up calls on every voice channel so you don’t miss anything. Because it’s a web interface, he can bring it up on his phone or tablet from anywhere. Greg thinks the next major SDR development will eliminate the need for any fully hardware based radios entirely. An SDR can do things that not a single hardware-based scanner out there is capable of. Greg has used his SDR to tune into his utilities smart meters for his water and gas to track his usage. One of Greg’s favorite things about SDR is that you can see the signals and whether they’re strong or not, whether they’re digital or analog, etc. The ability to visualize the signal lets you find a lot more new stuff to listen to. The flexibility of an SDR and ability to do so many things at once with it means you get the equivalent of several premium subscriptions to other services. All session notes with links to the items we talked about an be found on our website at www.scannerschool.com/session168

168 - Using a SDR as Your Scanner

Episode 165 - This is Why You Need an SDR

In this episode, Phil walks through the basics of what an SDR is, its history, and how you can get set up with one. The perfect introduction to his upcoming SDR webinar and course.

What you will take away from this week's podcast:

An SDR means that anything normally handled by the hardware of the radio is now handled by the computer, and the physical hardware serves as an interface. The only limitation on the SDR hardware you buy is the frequency range and the amount of RF it can digest. SDR receivers have come a long way since they were first hacked into existence. SDRs used to be difficult to set up, but that’s no longer true. You don’t need advanced computer skills to run SDR software. SDR software can run on PC, Linux, Mac, Raspberry PI, and even Android. An SDR is more flexible and less expensive than a traditional radio. You can turn a $30 USB stick into something as powerful as an SDS200 in an afternoon. All you need to get started is an SDR USB stick, a computer, and the free starter software SDR Sharp. Once you get set up with FM broadcast stations, aviation, and other analog systems, Phil’s SDR course will go into how to set up digital reception. If you download DSD+ Fast Lane or Unitrunker you can monitor trunking systems. All session notes with links to the items we talked about an be found on our website at www.scannerschool.com/session165

165 - This is Why You Need an SDR

Episode 164 - Raspberry PI and SDR w/ Fuzz the Pi Guy

In this episode, Phil talks to "Fuzz the Pi Guy".

Fuzz has a large YouTube channel and has a ton of SDR and Raspberry Pi Videos.

Fuzz and I discuss how he uses his Software Defined Radios and how he keeps costs down by using a Raspberry Pi as as his computer for many of these projects.

What you will take away from this week's podcast:

SDR stands for Software Defined Radio, where you plug your hardware into power on one end and your computer on the other end so the computer software can interpret the signal. The Raspberry Pi is essentially a low-cost computer to help teach computer science in schools, and is now used for things like hosting Minecraft servers, learning Linux, and running SDR programs. Fuzz has a YouTube channel where he primarily demonstrates Raspberry Pi projects and tips, as well as a wide variety of small electronics content. He’s using a new setup that involves a Raspberry Pi 3 with an RTL-SDR dongle, connected to a 2m 70cm homemade antenna to receive his local Phase 2 frequencies, uploaded to Broadcastify using the new free software OP25. Using this setup, Fuzz essentially created a Phase 2 scanner for under $100. The FlightAware website gives a good introduction to using the Raspberry Pi with an SDR that can get you set up in under 15 minutes. The Raspberry Pi has the best support system out there for any Pi hardware, but Fuzz has been working with the Atomic Pi lately. This setup provides an inexpensive alternative to buying a pricey scanner if you don’t mind troubleshooting and problem solving to get going. All session notes with links to the items we talked about an be found on our website at www.scannerschool.com/session164

164 - Raspberry PI and SDR w/ Fuzz the Pi Guy

NOAA-2 Returns from the Dead

Satellites can stay in orbit for years after their decommissioning date. Although they are turned off, often after many years they can turn on again as the battery chemicals begin to break down, eventually allowing electricity directly to the satellite systems whenever the solar panels are in light. We've seen this phenomenon occur with various decommissioned satellites.

Recently it was discovered by amateur radio satellite watcher Scott Tilley that NOAA-2 appears to be actively transmitting again in the L-band at 1697.5 MHz. NOAA-2 is a weather image satellite that was operational from 1972 - 1975.

Next over on his blog Derek OK9SGC was able to confirm reception of the signal, make a recording, and then with the help of @Xerbo10 discovered that you can actually receive an image from it. However as is to be expected the camera is not actually operational and all you get is a few grey lines indicating voltage calibration and sync telemetry.

It's unknown how long the satellite will stay undead, but if you manage to receive it let us know in the comments.

NOAA-2 Revival Signal and APT Image

SDR# Updated: Improved Performance and Better RTL-SDR Compatibility

SDR# (SDRSharp) is one of the most popular free software defined radio programs available with RTL-SDR support. Recently it has been updated to version 1811 and the new version brings improved performance and also improves RTL-SDR compatibility with some systems. The changelog reads:

Date:   Mon Mar 29 15:03:09 2021 +0200
Commit: d5cb6c3

More DSP optimizations;
Many fixes for RTL dongles (mainly workraounds for old libs);
Revert to libusb 1.0.20.11004 for backward compatibility;
Revert to portaudio 2016 for backward compatibility;
Code cleanup.

@lambdaprog (the SDR# programmer) has also tweeted showing how well SDR# can run on a 10 year old i7 4700 laptop with the new performance improvements. With a huge 160 MSPS baseband IQ file, the software is seen to be using very minimal CPU. 

Building a GOES-16 Antenna out of Trash, Cardboard and Foil Tape

Over on his YouTube channel saveitforparts has uploaded a video showing how he was able to modify and old DirectTV satellite dish found in the dumpster with cardboard and foil in order to receive images from the GOES-16 geostationary weather satellite.

I wanted to download images from the GOES-16 weather satellite, but didn't have a big enough satellite dish. So I made one out of an old TV dish, cardboard, and aluminum tape! Amazingly this actually works, and I was able to pull live pictures of the earth off the satellite in geostationary orbit! The cardboard won't last long-term, so I'm looking for an antique C-band dish that I can set up as a more permanent solution. However, for a cheap and expedient ground station, this worked pretty well!

Satellite Ground Station With Trash, Cardboard, and Foil Tape!

SMOG-1 PocketQube Satellite Successfully Launched and in Orbit

Thank you to Zoltan Doczi (HA7DCD) for submitting news about the successful launch and first reception of the SMOG-1 PocketQube Satellite (which is only 5x5x5cm in size). The pre-launch press release by Tech University of Budapest is available here, and the SMOG-1 Facebook page provided additional updates.

Back in April 2020 we first heard about the launch of SMOG-P which was the first functioning 1-PocketQube satellite, and was designed to measure electromagnetic pollution (electrosmog) from space. SMOG-1 is the successor to SMOG-P and it carries a similar mission to measure electromagnetic pollution generated by human activity in space around the Earth. Interestingly it also carries a magnetically lossy material under it's solar panels which is to act as a brake, reducing the 18-25 Orbital lifespan, thus reducing space trash after the primary mission is complete.

According to the receive and decoding instructions provided by Levente Dudas, SMOG-1 can be received with a simple satellite antennas, such as a handheld Yagi, Turnstile, Dipole or quadrifilar-helix antenna. The telemetry frequency is 437.345 MHz with callsign HA5BME. For the radio an RTL-SDR connected to a Raspberry Pi can be used, and the telemetry decoding software can be found on GitLab. 

SMOG-1 can be tracked here, although Zoltan mentions that the TLEs may not yet be accurate for several more days or weeks, as was seen with the launch of SMOG-P as well. The reason is that it is difficult for the NORAD radars to see these tiny PockQube satellites which is required for TLE generation.