Category: Amateur Radio

Creating an Open Source DMR Transceiver with a LimeSDR Mini

Thank you to Adrian Musceac for writing and sharing his article detailing how he implemented an open-source DMR (Digital Mobile Radio) transceiver modem with his LimeSDR Mini and GNU Radio.

DMR is a digital voice communications protocol often used by commercial business band radios, as well as by amateur radio hobbyists.

Adrian explains:

I wrote an article about the implementation of an open-source DMR transceiver using the LimeSDR-mini, GNU Radio and Codec2, which could be used for SDR experiments.

The DMR modem was designed to work both in repeater and direct (DMO) mode, and supports voice and other basic features of the ETSI TS 102 361-1 standard.

In the article there is discussion about aspects of the TDMA transmission, time synchronization, as well as how David Rowe's Codec2 can be used to replace the default vocoder.

The work builds upon Jonathan Naylor's extensive DMR implementation which a large number of amateur radio operators are using as part of MMDVM.

DMR TX Flowgraph
DMR TX Flowgraph
Transmitting DMR with the LimeSDR-mini

TechMinds: Testing out the SDRBerry Software on a Pi 4 with Touchscreen

Over on the TechMinds YouTube channel, Matt has posted a video demonstrating the SDRBerry software, which can be used with many SDR devices, including the RTL-SDR, on a Raspberry Pi with a touchscreen.

The SDRberry software is designed to be used on a touchscreen. As Matt points out, it has an aesthetically pleasing user interface and is compatible with almost any SDR software via the Soapy interface. Combining an SDR with a Pi 4 touchscreen and SDRberry results in an excellent hand-held SDR system.

In the video, Matt demonstrates the features of SDRberry, showing its RX features as well as some of its TX features, such as speech transmission and FT8, via a built-in WSjtx tab. He then shows the optional web interface, which is still in the early stages of development. Finally, he shows how to install the software and dependencies onto a fresh Raspbian image. 

SDRBERRY - This User Interface Is Just GORGEOUS! AND IT USES SOAPY TOO!

Setting up a Dual RX System with an SDR and Ham Radio Rig via an SDRSwitch

There are two common options when using an SDR together with a ham radio rig. You can either create an IF tap within your ham radio and connect the SDR to that, or connect the SDR directly to the antenna via a switch that switches the SDR out when transmitting.

Over on YouTube, Ham Radio DX has uploaded a video discussing the latter option and revealing its advantages. In the video, he mentions results by HB9VQQ that show that connecting an Airspy HF+ directly to an antenna via an SDR switch from SDRSwitch.com results in 60% more spots on WSPR, compared to using an IF tap from an FT450D ham radio rig.

He goes on to explain and demonstrate his setup and the recommended switch that he is using, which is the SDRSwitch by N2EME, available at SDRSwitch.com. He notes that this switch is recommended due to its very low insertion loss and high isolation specifications and compares it against an MFJ switch, which has some rather terrible specifications.

Add a SDR Receiver to ANY Ham Radio Rig!

HOPE XV Conference 2024: Ham Radio for Hackers Talk Video

Back in July 2024 we posted about Dan's (KB6NU) talk at the HOPE (Hackers of Planet Earth) conference about how Ham radio can be for hackers, and how hackers are the future of ham radio. Back then only the slides were available.

The video of the talk has recently been uploaded to YouTube, and is embedded below. The talk emphasizes how ham radio is not only about the traditional thought of making contacts, which is probably in most people's heads, but also about hacking radios, antennas, microcontrollers, satellites, pico balloons, digital communications, GNU Radio, and more. Dan mentions his goal is to promote ham radio to the much younger hacker crowd, where he believes it is underrepresented.

HOPE XV (2024): Ham Radio for Hackers

Building an “HF Helper” for Improving RTL-SDR HF Reception

Over on YouTube Amateur Radio VK3YE has uploaded a video showing his 'HF Helper' project. The HF Helper is a tunable HF filter and attenuator that helps improve HF reception when in the presence of strong overloading signals. VK3YE writes:

Using an RTL-SDR.COM dongle (genuine model V4) and a computer with SDR Sharp you can get quite good reception of HF signals. However reception can sometimes be spoiled by overload from signals on or away from the desired reception frequency. The 'HF Helper' presented here can reduce these problems. And you can use it in conjunction with a QRP transmitter to form a simple transmitting station.

RTL SDR HF Helper improves reception

Also as a bonus, in a related video VK3YE also shows the RTL-SDR Blog V4 being used on SDR Touch on an Android phone for portable HF, VHF and UHF reception.

Hear HF VHF UHF on an Android phone

Ham Radio for Hackers

Over on Hackaday we've seen a post about Dan's (KB6NU) talk at the HOPE (Hackers of Planet Earth) conference about how Ham radio can be for hackers, and how hackers are the future of ham radio. Hackers in this context mean people who enjoy experimenting with electronics, building stuff, and understanding how things work.

Dan's slides have been uploaded on his blog. The slides emphasize how ham radio is not only about the traditional thought of making contacts which is probably in most people's heads, but also about hacking radios, antennas, microcontrollers, satellites, pico balloons, digital communications, GNU Radio and more. Dan mentions his goal is to promote ham radio to the much younger hacker crowd, where he believes it is underrepresented.

Ham radio for hackers
Ham radio for hackers

SignalsEverywhere: Decoding the QO-100 Mid-Beacon with WebSDR and IZ8BLY’s Decoder

In one of her latest videos on YouTube, Sarah from the SignalsEverywhere channel shows how we can use a program called "IZ8BLY Phase 3D (AO-4) Satellite Decoder" to decode the 'Mid-Beacon' on the QO-100 satellite. QO-100 is a commercial geostationary communications satellite that also contains a popular transponder for amateur radio.

However, there is also an interesting beacon called the mid-beacon that can be decoded, which provides some information about the satellite. In the video, Sarah shows how this beacon can be decoded with the software from IZ8BLY. As QO-100 is only visible from Europe, the Middle East and Africa, Sarah uses a WebSDR to receive the signal from the USA, then pipes the audio into the IZ8BLY decoder via Virtual Audio Cable.

Decode QO-100's Mid-Beacon with Virtual Audio Cables and WebSDR

An Atmega328 + SI5351 Based WSPR Beacon

Thank you to Ihar Yatsevich for writing in and sharing with us his open-source WSPR beacon project. The WSPR beacon consists of a custom PCB with ATMega328 microcontroller, GPS module, single transistor amplifier, and Si5351 with TCXO.

The result is a very simple, portable WSPR beacon that can be heard all over the world. However, it appears that no band filters are built into this, so you will need to add a bandpass filter for the WSPR band that you are using.

WSPR (Weak Signal Propagation Reporter) (pronounced "whisper") is an amateur radio digital HF mode designed to be decodable even if the signal is received with very low power. Because of this design, even low-power transmitters can be received from all over the world. It can also be used to help determine HF radio propagation conditions as WSPR reception reports are typically automatically uploaded to wsprnet.

If you are interested, Ihar has written about his project in more detail over on Reddit. 

Ihar's Microcontroller Based WSPR Beacon
Ihar's Microcontroller Based WSPR Beacon