A SDR Digital Voice Hotspot with GNU Radio, MMDVM and QRadioLink

Thank you to Adrian (YO8RZZ) for writing in and sharing with us his article explaining how to use an SDR to set up a digital voice hotspot for digital voice modes supported by MMDVM such as D-Star, DMR, System Fusion, P25 and NXDN. Adrian notes that this is possible with any full duplex SDR such as the LimeSDR or PlutoSDR, or with a combination of simplex devices, such as a HackRF for transmitting combined with an RTL-SDR for receiving.

MMDVM is firmware that normally runs on an ARM microcontroller board such as the Arduino Due, and is designed to be interfaced with hardware radios via the microcontrollers built in ADC and DAC hardware.

In order to use an SDR instead of physical hardware radios, Adrian's article describes how a fork of MMDVM called MMDVM-SDR is used in his system as this allows the code to run on a normal Linux computer with an SDR. GNU Radio running on Adrian's own QRadioLink software is then used to create software ADC/DAC interfaces for the SDR and MMDVM-SDR to interface with, as well as providing a user interface.

QRadioLink used as the UI for MMDVM-SDR and GNU Radio
Tweet19
Share
Reddit
Vote
Email
19 Shares

RTL-SDR Blog Active L-Band Patch Antenna for Inmarsat, Iridium, GPS Back in Stock

Just a quick note to say that the second batch of our Active L-Band Patch Antenna for receiving Inmarsat, Iridium and other L-Band satellites is now in stock, available to be shipped from our warehouse in China from early next week. Amazon will be stocked within the next 1-2 months as the freighter will take time to arrive.

Please see our store for ordering details.

Apologies as we've had to temporarily suspend sales of this product as a manufacturing defect has been discovered in this batch. The defect is that on a number of units the plastic around the screws is cracking, and this was caused by a factory worker over torqueing a pneumatic screwdriver.

The antenna itself will work fine, and it probably won't even affect weather tightness, but it is certainly a defect. If your unit already shipped out and your unit has these cracks, please let us know at [email protected] and we will get the factory to ship you a replacement enclosure. For unshipped units we will be issuing a refund within the next few days.

Update: The units have been repaired and are available for shipping again.

Pricing remains the same at US$49.95 including free worldwide shipping to most countries. A reminder to EU customers: please order from our Aliexpress or eBay stores as due to the new IOSS laws we need to now use those marketplaces to collect and remit VAT upon your purchase, instead of upon import at the border.

This second batch comes in a gray color as feedback from the previous batch indicated that a lighter color is preferred to avoid excess heating from the sun.

If you are hearing about this patch antenna for the first time, please see our original release post for more information. In short this is an amplified patch antenna designed to be used with bias tee capable SDRs that can provide 3.3V - 5V power, such as our RTL-SDR Blog V3 dongle, Airspy, SDRplay or HackRF.

The antenna allows for reception of L-band satellites that transmit between 1525 - 1660 MHz, such as Inmarsat, Iridium and GPS. Please note it is *not* for receiving weaker signals like HRPT and GOES which require a dish antenna.

The patch comes with useful mounting accessories including a window suction cup, bendable tripod and 3M RG174 coax cable. The patch and active circuitry is enclosed in a weather proof enclosure.

What can you do with this antenna?

Tweet
Share
Reddit
Vote
Email

Simple FM Radio and Airband RTL-SDR Android Applications

On the Google Play store developer Knowle Consultants have recently released a new free application called "FM Radio (RTL-SDR)". This is a simple app that allows you to use a connected or remotely networked RTL-SDR to tune into preset broadcast FM stations. People wishing to use an Android enabled head unit in their car may be interested in the app as it makes tuning into broadcast FM stations easy just like it is on a standard radio.

They also have a similar app called "Airband Radio (RTL-SDR)" which provides a similar simple interface for tuning into airband presets.

Knowles Consultants simple Android RTL-SDR FM and Airband Receiver Apps
Tweet14
Share
Reddit10
Vote
Email
24 Shares

SDRA2021 Talks: Electrosense, Neural Network Signal Classification, gr-rpitx, Radio Astronomy and More

The 2021 Software Defined Radio Academy conference was held online this year on June 26/27 and the talks have been recently uploaded to YouTube. There are some interesting talks this year including a presentation on various SDR related topics including Electrosense, gr-rpitx, 21cm radio astronomy with low cost SDR hardware, and using deep learning neural networks for automatic signal identification. Our favorite talks and blurbs are collected below for easy access, and the full set of talks can be found on their YouTube channel.

Dr. Henning Paul: Building a flexible Multi-Antenna-capable SDR using open Source

The availability of Open Source software components enables the ambitious hardware hacker to design their own powerful SDR. This talk is the follow-up to the talk on Scientific SDR and recapitulates the steps towards the current design of a Homebrew SDR based on a Xilinx Zynq SoC using the Linux kernel and other Open Source components. Furthermore, one of its applications, receiving shortwave radio with antenna diversity is presented.

SDRA2021 - 04 - Dr. Henning Paul: Building a flexible Multi-Antenna-capable SDR using open Source

Jean-Michel Friedt: GNURadio compatible gen. purpose SDR emitter using RasPi4 PLL

GNU Radio, the Raspberry Pi single board computer and Digital Video Broadcast Terrestrial receivers make an awesome combination for educational purposes of Software Defined Radio. gr-rpitx aims at complementing these tools with emitting capabilities, combined with the flexibility of GNU Radio.

SDRA2021 - 08 - Jean-Michel Friedt: GNURadio compatible gen. purpose SDR emitter using RasPi4 PLL

Sreeraj Radjendran: Knowledge extraction from wireless spectrum data

In this half-hour talk, the need for large scale wireless spectrum monitoring will be discussed. A short introduction to a large scale wireless spectrum monitoring framework, Electrosense, will be given. Furthermore, how anomaly detection and signal classification can be performed using the collected data will also be discussed. Insights to the major problems with state-of-the-art machine learning models will also be discussed in this context.

SDRA2021 -11- Sreeraj Radjendran: Knowledge extraction from wireless spectrum data

Stefan Scholl, DC9ST: Classification of shortwave radio signals with deep learning

Automatic mode classification of radio signals in the HF band is a valueable tool for band monitoring, operation of rare transmission modes and future applications of cognitive radio. In recent years, machine learning has established as a general and very powerful approach to classification problems. The presentation first provides an introduction to neural networks and deep learning. Then neural nets are applied to the task of radio signal classification. The result is an experimental deep convolutional neural net (CNN), that can distinguish between 18 different transmission modes occurring in the HF band, such as AM, SSB, Morse, RTTY, Olivia, etc.

Additional Links: Stefan Scholl's post on this topic 

SDRA2021 -12- Stefan Scholl, DC9ST: Classification of shortwave radio signals with deep learning

Marcus Leech: Mapping the sky at 21cm: Gnuradio and Radio Astronomy

We show the results of a year-long sky survey at the 21cm hydrogen line, producing an intensity map of the sky covering a declination range from -35 to +75DEG. We discuss the software tools used, Gnu Radio signal flows, and the hardware aspects of the instrument.

SDRA2021 -14- Marcus Leech: Mapping the sky at 21cm: Gnuradio and Radio Astronomy

Tweet31
Share
Reddit
Vote
Email
31 Shares

TechMinds: Testing the SDRUno ADS-B Plugin Beta

This week on the Tech Minds YouTube channel Matthew tests out the SDRuno ADS-B aircraft tracking plugin beta. SDRuno is the official software for the SDRplay RSP line of receivers, and the beta can be downloaded from their website (note the plugin will not work for the RTL-SDR).

In the video Tech Minds shows how to set up SDRuno to work on his active ADS-B antenna by activating the bias tee, and how to load and activate the ADS-B plugin. He goes on to show how you can then use another program called Virtual Radar Server to connect to the ADS-B plugin data output, and plot local aircraft on a map.

He notes that the plugin itself will have it's own map display available via a web browser, however in the current beta the mapping output is incorrect.

SDRPLAY SDRUno ADSB Plugin - Tracking Aircraft Easy

Tweet
Share
Reddit
Vote
Email

DragonOS: Automated Spectrum Analysis with SDR4Space.lite

Over on YouTube Aaron has uploaded a video showing how he is using the SDR4Space.lite package in DragonOS to do some interesting experiments with automated spectrum analysis using a PlutoSDR or RTL-SDR. As a reminder, Aaron is responsible for DragonOS which is a Linux OS with many SDR software programs preinstalled (including SDR4Space.lite).

This video shows how to use the RTLSDR/PlutoSDR with some of the prebuilt SDR4space.lite javascript examples preinstalled in DragonOS Focal.

I start out showing the new IQ recording script w/both the RTLSDR or the PlutoSDR. After a recording is triggered, the saved file can be looked at with inspectrum, SigDigger, etc. The javascript itself can be modified to produce desired results, but by default it's setup to record POCSAG.

The second half of the video shows how to use the wide spectrum analysis javascript to look at 88-108Mhz. The script produces a graphical representation of the RF spectrum along with a spreadsheet containing the corresponding RF information.

Any of these scripts can be modified, new ones can be built, and cron jobs or other scripts could call upon them as needed. I hope to do more videos once I figure out how to take the data and put it into some sort of database.

DragonOS Focal Automate Spectrum Analysis + IQ recording w/ SDR4space.lite (RTLSDR, PlutoSDR) part 1

Tweet21
Share
Reddit24
Vote
Email
45 Shares

A Facebook Group about 10GHz Experiments for Beginners

Thank you to Jean Marie (F5VLB) who has written in and wanted to share an invitation to their Facebook group where they are discussing ways for beginners to get into low cost 10 GHz (SHF) experiments. The 10 GHz band is generally considered tough to break into due to the precision required at these frequencies, however Jean notes how they are making use of readily available TV LNBs, RTL-SDRs and free software for their experiments. Jean writes:

I would like to present to you here about a Facebook group that addresses (only) radio enthusiasts, whether it is SWL or loose amateur radio and are interested in the high bands (SHF). On my life of Ham Radio I have never found a site that explains clearly, without big expenses, how to explore these bands.

The purpose of this FB group is to gently take you to this world, reserved for the experts, and yet accessible with reasonable means, with facilities found in the TV SAT store from the corner of the street. For some 50$ you will be ready with a dish, a lnb, a tx module.

The site begins. In 3 weeks 116 members came to join us. We go slowly, step by step.

The result ? It will listen to a satellite at 36000km, listening to tags everywhere around you, emit (if you have the license) on these mythical bands of 10 and 5.7 GHz.

This is aimed at young people aged 7 to 77, without special knowledge.

Want to know more ?

So come on https://www.facebook.com/groups/bzh10ghz this site is for you. And for others who are far in front of us, do not hesitate to bring your comments, simple, kind and taking into account that this site is made for newbies.

10 GHz Equipment and Group (Images provided by Jean Marie F5VLB)
Tweet27
Share
Reddit
Vote
Email
27 Shares

Arinst SDR Dreamkit: A Portable RX SDR with 16-Bits, 1 – 3100 MHz Range and 5 MHz Bandwidth

Thank you to reader 'sunny' who has written in to share a new software defined radio that he has found being previewed on YouTube. The SDR is the Arinst SDR Dreamkit, a Russian made portable receive only SDR that will have a 16-bit ADC, 1 - 3100 MHz tuning range, up to 5 MHz instantaneous bandwidth, and have very fast processing which can scan the spectrum at 20 GHz per second. It also comes with a built in 3.9" touchscreen and loudspeaker.

Arinst are a Russian company that designs, produces and sells affordable portable spectrum analyzers, vector network analyzers, power amplifiers and antennas.

The Dreamkit is not yet available for sale but reader sunny has indicated that the pricing will be ~$250, although we cannot confirm that information. In a YouTube comment the developer only writes that it will be slightly more expensive than the Malachite SDR, for which an original non-clone unit sells for around $200. 

The Arinst SDR Dreamkit

We have not seen any announcement of the product on their website, but on their first YouTube video for the product they write some specs (translated from Russian):

  • There is no preselector.
    • Possibility to supply preselectors and source repeaters via SMA antenna connector. It also provides for the generation of a code message for each frequency range by pulse modulation of the supply voltage supplied to the antenna connector.
  • Operating frequency range - 1-3100MHz
  • Input impedance 50 Ohm.
  • ADC capacity - 16 bits, effective 13 bits.
  • Instant scan bandwidth - 5 MHz, sampling rate: 2 IQ channels at 6 MHz.
  • Scanning speed over 20 GHz per second.
  • Audio: built-in loudspeaker, headphones, bluetooth (optional).
  • Battery life up to 3 hours.

From the English demo video shown below, the interface looks very slick, customizable and with a very responsive refresh rate. The video shows off the features which include all the standard demodulation modes, an RDS decoder, 12V 100mA bias tee, and the ability to connect to a PC and run it on HDSDR.

It appears that they plan to sell additional preselectors and LNAs that will be powered via the 12V bias tee. An interesting point is that it appears that they will control the external devices via a some sort of modulated pulse on the coax.  

Arinst SDR Dreamkit V1D

Tweet32
Share
Reddit
Vote
Email
32 Shares