Over on GitHub a new open-source program called 'PySpecSDR' by [xqtr] has recently been released. This is a full multipurpose SDR receiver program like SDR# or SDR++, but with the difference that it runs entirely with a text user interface.
PySpecSDR displays a real-time spectrum and waterfall via text user interface and has the ability to demodulate and play audio for FM, AM, and SSB signals. The software also includes features like a scanner, automatic signal classification (between digital, FM, AM), frequency bookmarks, AGC, recording capabilities, band presets, and a configurable display. It is completely controlled via keyboard shortcuts.
Currently, the first version supports RTL-SDR only, but there is another version being worked on in the repo called pyspecsdr-soapy.py. This version uses SoapySDR, and that should support almost every SDR. It appears that most SDRs should already be working, but there are still some quirks to be fixed.
Thank you to RTL-SDR.COM reader Steve Hagerman for writing in and sharing his Python script that allows SDR++ users to convert a CSV file of frequency bookmark information into a JSON file that SDR++ recognizes. Steve explains:
[In SDR++] one of the biggest issues is in making frequency bookmarks. SDR++ uses a JSON file to store frequency bookmarks which is hard to edit manually. While there is a direct means to enter bookmarks directly in SDR++, it is tedious and requires too many mouseclicks.
To fix this I wrote a Python script to take easily made XLSX Spreadsheet of frequencies to convert to a JSON file that can be used directly with SDR++.
Recently Salil (aka NUCLEARRAMBO) uploaded a blog post on his website detailing how he designed and tested a low noise amplifier (LNA) with a filter for 130 - 160 MHz, which is useful for improving reception for the Meteor M2 LRPT weather satellite. If you were unaware, an LNA can help improve the reception of an SDR by reducing the noise figure of the system, and by overcoming losses from long coax cable runs. The filter helps reduce the strength of out-of-band signals which if too strong, can desensitize and cause imaging on the RTL-SDR.
In his design, Salil used a PGA-103+ LNA chip which has excellent noise figure and OIP3 specifications. His blog post details how he designed the circuit around the PGA-103+, added a bias tee for power, and how he designed the filter.
In part 2 of his post, he details how he tested the LNA+filter combinations frequency response, input voltage range, noise figure, and bias tee with an RTL-SDR Blog v3 and a NanoVNA V2.
Over on his YouTube channel Aaron, creator of the DragonOS image (a Linux image with many built-in SDR compatible programs) has uploaded a new video showing how it is possible to run the Windows only AISMon software on Linux, using WINE. WINE is a Windows emulator for Linux which allows users to run some Windows software on Linux.
In the video Aaron shows how to set up WINE on the DragonOS Linux image, how to run AISMon with it, and how to set up the Virtual Audio Cable sink which is required to pass the audio from SDR++ to AISMon. He also shows how he tests his setup using the AIS-Simulator software with a HackRF, and an RTL-SDR for receiving.
Over on his YouTube channel, TAKEAPART has recently uploaded a new video showing how to set up a cheap ADS-B FlightAware feeder using an RTL-SDR Blog dongle, and a Raspberry Pi Zero 2W. The Raspberry Pi 2W is a US$15 computer that is capable of running the PiAware ADS-B feeding software which uploads ADS-B data to the FlightAware.com flight tracking service. If you are a contributor to this service, you can get a Premium FlightAware subscription for free.
In the video, TAKEAPART shows how to install the PiAware software on the Pi 2W, and how to configure the PiAware settings. Finally, he shows it in action, receiving flight data with a homemade 1/4 wave ground plane antenna.
Cheapest ADS-B feeder RTL-SDR and Raspberry Pi Zero 2W (PiAware/FlightAware)
Over on the /r/amateursatellites subreddit, user elmarkodotorg is organizing a group megaprojection project. The Megaprojection Project seeks to create a composite of as much of the earth as possible from weather satellite images captured by hobbyists in a single day, via data from NOAA and Meteor polar-orbiting satellites. They will be accepting HRPT or LRPT data from either Nov 30 or Dec 1 (date yet to be confirmed).
Hobbyists can receive these satellites' LRPT and HRPT signals using an RTL-SDR and appropriate antenna setup.
If you want to contribute, you can join DerekSGC's Discord server, https://sgcderek.github.io, where coordination will be carried out. elmarkodotorg writes that currently, they have confirmed contributors with stations from the west coast of the US all the way over to the western edge of Asia. Currently, they are still hoping to find contributors from the Canary Islands, Turkey, Equatorial Africa, the general area of Indonesia, and Northern Australia. In a more recent Reddit thread, elmarkodotorg provides a link to a Google docs sheet, where you can also register interest.
Recently, on November 16 a test was carried out and they were able to successfully combine 24 images received across the world.
Megaprojection Nov 16 Test: 24 contributors from all over the world submitted HRPT and LRPT images received from their home satellite ground stations.
Thank you to RTL-SDR.COM reader David for letting us know about an excellent talk from Charles Lohr (@cnlohr) at the 2024 Hackaday Supercon about turning microcontrollers into radios by abusing their output GPIOs to create RF generators.
This talk explores ways to leverage every cycle of underpowered microcontrollers to get them doing the work of parts ten times their price, including operations normally done with dedicated radio hardware.
This is a concept we have seen quite often before in projects like RPiTX and Osmo-FL2K which turns a Raspberry Pi and cheap VGA adapter respectively, into an arbitrary RF signal transmitter with no transmit components required.
In his talk Charles Lohr takes this concept further, showing how almost any microcontroller like an ATTiny85, ESP8266, CH32v203, and ESP32-S2 can be turned into a transmitter. In the talk, Charles shows how he used the I2S bus on an ESP8266 to transmit NTSC color video to a TV and transmit LoRa via his LoLRa software. He then notes that he was able to use the ESP32-S2 to transmit LoRa over 2.5 miles away.
Finally, Charles shows how the CH32v203 microcontroller can also be used as a receiver. With some code he wrote he is able to display the received signal on an FFT computed directly on the CH32v203, and even have a web interface to tune to specific frequencies and playback AM audio.
Hackaday Supercon 2024 - Microcontrollers Are Just Radios in Disguise - Charles Lohr
CNLohr's own YouTube video on the topic is also an excellent overview.
How far can I broadcast LoRa packets WITHOUT a radio? - LoLRa
Recently Majodi from NickStick Design wrote in and wanted to share with us some updates to the 'NickStick RF PowerSnitch' which we previously posted about in 2021. The PowerSnitch is a device that can be used to gain a quick insight into RF power levels. This is useful to help prevent exposing your expensive and sensitive RF equipment, like an SDR or VNA, to excessive power levels that could destroy it.
The device uses three LEDs to tell you the power level. Green means you have a safe power level, caution is yellow and danger is red. Yellow is set to around 0 dBm.
The RF PowerSnitch is available on Tindie or lectronz for US$29.50.
In a recent re-release, they replaced the micro USB port with a USB-C power port. They write:
Today, NickStick Design, an electronics design company for Makers, is excited to announce the launch of the RF Power Snitch USB-C, the newest version of its popular RF Power Snitch device. This updated model replaces the micro-USB port of the original with a USB-C port, making it more versatile and future-proof for today’s connectivity needs.
“Our original RF Power Snitch saved many VNA devices from destructive power levels” Majodi of NickStick Design said. “With the RF Power Snitch USB-C, we’re excited to provide users with an upgrade which aligns with modern connectivity standards.
Over the years many more products in the RF domain became accessible to radio enthusiasts. RF Power Snitch is a valuable companion tool for checking the potentially destructive power of the signals one would want to feed to their equipment. Because, although tools like the TinySA, NanoVNA or SDR devices are extremely affordable today, for a maker it is still an investment worth protecting.
That’s why our goal was to develop a low-cost companion device that can help makers and experimenters (especially beginners) in the RF domain to gain insight in the power levels of a signal before hooking things up to their valuable test equipment. As an extra to this we also made it possible to attach an MCU for doing power readings and plotting.
