Back in 2018 we posted about someone who had combined an ultrasonic piezo speaker and an SDRPlay RSP1A in order to create a device that can detect the ultrasonic sonar sound from bats.
Recently on YouTube Matt from the TechMinds YouTube channel was able to create a similar system using a MEMS microphone from Knowles which can receive audio in the 100 Hz ~ 80 kHz range. He connects the microphone to a 3.3V supply and connects the output of the microphone to his SDRplay RSPDx.
The system was then able to successfully hear the sound of bat sonar at his home location in the UK.
Ultrasonic BAT Detector Using Software Defined Radio
In his latest video Matt from the TechMinds YouTube channel shows us how to build a home made turnstile antenna for receiving the MILSAT SATCOM satellites where radio pirates from Brazil and other countries can often be heard.
The build involves 3D printed parts, metal measuring tape for the elements, some aluminum tubes and a coax phasing harness. After testing the VSWR with a meter, Matt tests the antenna with a handheld and finds it to be working well. He also later tests it with his SDRplay RSPdx and finds that the Turnstile outperforms his roof mounted vertical.
Back in March of this year we posted about an OpenWebRX fork called OpenWebRX+, which adds multiple built-in and ready to use decoders such as SSTV, AIS, CW and RTTY. OpenWebRX+ is a fork of the OpenWebRX project which is now officially maintained by DD5JFK.
Since our last post OpenWebRX+ has progressed in development further, and now includes a HFDL decoder via dumphfdl, various ISM band equipment decoders via rtl_433, FLEX pager decoding via multimon-ng, and a SELCALL decoder has also been added. Many other improvements and changes to the software have also been added, and the full changelog can be viewed here.
OpenWebRX+ is software for Linux. If you want to install OpenWebRX+, an easy path is to use the ready to use Raspberry Pi 4 image available on the releases page, or to use their PPA.
SSTV Image received by the luarvique fork of OpenWebRX. Credit: Neil Howard
In his latest video Matt from the TechMinds YouTube channel has shown how it's possible to detect the RF echoes of meteors falling in the earths atmosphere which a software defined radio.
The concept is relatively straightforward. Meteors falling in the atmosphere generate an RF reflective ionized trail, which is highly reflective to RF. In the UK where Matt lives, the Sherwood Observatory of the Mansfield and Sutton Astronomical Society (MSAS) have set up a meteor detection beacon "GB3MBA" which transmits an 80W CW signal at 50.408 MHz.
When tuned to this frequency with an SDRplay RSPdx SDR, Matt shows how the shifted reflections of meteors can be seen as blips around the beacon's carrier frequency. What is also seen are reflections from aircraft which show up as longer doppler shifted lines. Matt notes that if you live within 200km of the beacon a simple dipole antenna is sufficient, however any further might require an antenna system with more gain like a Moxon or Yagi.
We note that in Europe a similar beacon called the GRAVES space radar in France which operates at 143.050 MHz can be used.
GreenCube is a CubeSat by the Sapienza University of Rome, and it is designed to demonstrate an autonomous biological laboratory for cultivating plants onboard a CubeSat.
While this is an interesting mission in itself, for amateur radio operators there is another interesting facet to the satellite. Unlike most CubeSats which are launched in Low Earth Orbit (LEO), GreenCube was launched higher in Medium Earth Orbit (MEO) which provides a larger radio reception footprint over the earth. The satellite also contains a digital repeater (digipeater) at 435.310 MHz, which allows amateur radio operators to transmit digital radio packets up, and have the satellite repeat the packet back over a wide area footprint on earth.
Over on his latest video, Matt, from the TechMinds YouTube channel shows us how to receive and decode the packets from the GreenCube digipeater. In his demonstration Matt uses an SDRPlay RSPdx as the receiver, SDR++ as the receiver software, SoundModem as the packet decoder, GreenCube Terminal for displaying the messages, and GPredict for tracking the satellite and compensating for the doppler effect. He also notes that while a directional antenna on a motorized tracker is recommended, he was able to still receive packets with his omnidirectional terrestrial antennas without much issue.
Guglielmo is a Linux, Windows (and in this recent update x86 MacOS) based RTL-SDR FM and DAB tuner software that supports SDRs including the RTL-SDR, Airspy, SDRplay, HackRF and LimeSDR. It is designed to be an easy to use program designed for media users, rather than hobbyist technical users.
Regarding the release of Version 0.5, Marco writes:
This release sports full mac (x86 only, sorry) and windows installers, DAB and FM scans and a preset editor.
Over on our store we've just reduced the price of the remaining stock of our RSP1A metal enclosure upgrade set. The price reduction brings it down to US$29.95 including free shipping to most countries.
This is a premium aluminum metal upgrade enclosure for the SDRplay RSP1A. It helps block RF interference and protects the RSP inside the sturdy enclosure. This is most likely to be our last production of this enclosure at least for a long period of time.
The kit includes 1x black aluminum metal enclosure with two labelled side panels, 1x black semi-hardshell carry case, 1x thermal pad to keep the RSP1A cool and mechanically stable inside the enclosure, 1x accessory set including enclosure screws, GND lug bolt set and 3M anti-slip rubber feet.
Please note that the set does NOT include the RSP1A.
The sale will only be available while stocks last. There are less than 50 units available from our international platforms, and less than 130 available at Amazon USA. So get in quick before they are all sold!
OpenWebRX is an open source web based SDR receiver program that allows you or others (if you allow them to), to access your SDR over the internet. It is compatible with KiwiSDR, RTL-SDR, Airspy, SDRPlay and many other software defined radio hardware. It was originally developed by Andras Retzler, but since abandoned by him, with a semi-official fork being maintained at openwebrx.de. However, other forks like luarvique can exist that implement a new set of features.
The full set of additions and improvements reads as follows:
This is the package repository for the improved version of the OpenWebRX online SDR. The new and original features available in this version of OpenWebRX:
Built-in SSTV decoder with background decoding.
Built-in AIS decoder.
Built-in CW decoder.
Built-in RTTY decoder.
Built-in MP3 recorder for received audio.
Image browser for received SSTV images.
Adjustable noise filtering based on spectral subtraction.
Adjustable tuning step.
Improved touch screen operation, with panning and zooming.
Improved scroll wheel support, with tuning and zooming.
Improved tuning in CW mode.
Bandpass filter adjustable with scroll wheel.
More reliable SDRPlay devices operation.
Better map information, with distances.
Better APRS map information, with weather.
Configurable session timeout, with a policy page.
HTTPS protocol support (requires SSL certificate).
The code comes packaged for Ubuntu 22.04 (amd64, arm64) and Debian 11 (amd64 arm64, armhf). There is also a ready to use Pi 4 SD card image available, linked on the GitHub readme. The original forked code can be found at https://github.com/luarvique/openwebrx.
According to discussion over on the OpenWebRX groups.io, the fork also runs on a Pi 3. In the image Neil Howard from the groups.io forum demonstrates an SSTV image he received with an SDRplay clone using the luarvique fork of OpenWebRX.
SSTV Image received by the luarvique fork of OpenWebRX. Credit: Neil Howard
Stefan also notes:
The maker of OpenWebRX+ Marek and also the maker of the original version of OpenWebRX Jakob are reachable via a Telegram channel: https://t.me/openwebrx_chat
