Tag Archives: Software Defined Radio

Hamvention Highlights: The QRP Labs QSX 10 watt, general coverage, low-cost HF transceiver kit

Hans (G0UPL) of QRP Labs holding a QSX transceiver prototype at the 2019 Hamvention

Each year at the Dayton Hamvention I enjoy checking out the latest radio products and services. This year (2019) I found an exceptional number of innovations and will share these in Hamvention Highlights posts. If you would like to check out 2019 Hamvention Highlights as I publish them, bookmark this tag: 2019 Hamvention Highlights

The QRP Labs QSX Transceiver

Hans (G0UPL) of QRP Labs was, without a doubt, one of the most popular guys at the 2019 Hamvention — especially within the QRP community. In fact, at the Four Days In May (FDIM) vendors’ night his table was so busy I didn’t bother trying to force my way through the crowd to speak with him.

As luck would have it, our own table for ETOW was directly across from QRP Labs table at the the Greene County Fairgrounds so, in the end, I spent some quality time with Hans over the course of the Hamvention.

I’ll also make prediction: if the 10 band QSX transceiver delivers what it promises, it will be a serious disruptor in the ham radio transceiver world! This is a good thing. Why?

The QSX is a feature-packed, all-mode, high-performance, affordable, QRP transceiver.

The QSX will have a 24-bit Analog to Digital Converter (ADC) and a 24-bit Digital to Analog Converter (DAC). It will be a fully stand-alone unit and, since it’s an SDR and sports robust DSP, when connected to your PC, it will be recognized as a high-performance sound card. This equates to nearly native digital mode integration without the need for an external sound card interface.

The QSX Prototype Back Panel

The QSX Transceiver will be a through-hole kit with the surface-mounted components pre-installed on the circuit boards. This means the kit should be accessible to anyone with soldering skills.

Hans has even managed to include a mini spectrum display on the front backlit LCD panel.

The price? Around $150 US in total for the transceiver kit, 10 band filter module and enclosure. Unbelievable!

If Hans can pull this off — and I feel pretty confident he can — the QSX will set a new bar for QRP transceiver pricing and performance.

If you’d like more details about the QSX transceiver, check out the following resources sent to me by SWLing Post contributor, Pete Eaton:

The 10 band QSX will sport a general coverage receiver and although though the modes supported currently don’t include AM, Hans plans to add AM for at least reception purposes. This could make for a high-performance stand-alone SDR field radio for HF broadcast listening.

Of course, I also see the QSX transceiver as an accessible entry radio for new ham radio operators who are nervous about forking out $800+ for a new HF transceiver.

I will certainly grab the 10 band QSX transceiver kit when it becomes available and review it here on the SWLing Post. Stay tuned!

If you would like to follow other Hamvention Highlights, bookmark the tag: 2019 Hamvention Highlights

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The Airspy HF+ Discovery: A new high-performance SDR

At the 2019 Hamvention, I stopped by the Airspy.US booth and checked out the specifications of Airspy’s latest SDR: the Airspy HF+ Discovery.

At first glance, the Discovery looks a lot like the Airspy HF+ but even smaller and sporting performance upgrades. Keep in mind, I consider the Airspy HF+ (the Discovery’s predecessor) to be one of the best HF SDR receivers on the market–certainly the best sub $200 HF SDR–so of course the Discovery has piqued my interest.

I wanted to get the scoop directly from the source, so I contacted Youssef Touil with Airspy and asked for more insight. What follows is Youssef’s reply:

This new release of the HF+ aims to improve the overall performance in highly demanding situations while fully automating the gain and filtering control. This frees the operator from the RF front-end details and keeps the focus on the actual signals.

The new filters are implemented using a combination of static LC filter banks and other RC filters implemented in silicon. This considerably improves the overall behavior in a crowded band, while still giving a very low noise floor. Also, the very nature of the Polyphase Harmonic Rejection mixer combined with the integrated IF filtering and the high dynamic range Sigma-Delta ADC act like a roofing filter in a heterodyne system. This architecture is quite original with still very few commercial implementations attempted.

A lot of attention went to improve the far-range IIP2 and IIP3 in practical receive scenarios. Other radios just opt to increase the noise figure of the radio to hide the IMD problem, but this also reduces the sensitivity. We opted not to go this way and fix the problem at its root and preserve the maximum sensitivity benefit. The new intercept points protect the front-end from images originating from various IMD scenarios while still using the maximum gain. The LF and VLF bands also benefited from these improvements.

The PCB layout was also improved to get rid of most of the digital noise. The new PCB has 6 layers filled with ground plans and a metal shield can soldered on top of the RF section. This might look overkill for a HF/VHF radio, but given the MDS we are aiming at, it’s really necessary. The older PCB was 4 layers only.

The radio weighs less than 30 grams and fits inside a 45 x 60 x 10 mm volume (ex. The SMA connector). Given the achieved performance and the form factor, we expect it to interest a lot of our SIGINT partners who are already using the first HF+ design.

As you know, when it comes to high performance, the big players still opt for heterodyne systems in the actual RX path and only use direct sampling for the “eye candy” panoramic view. This was confirmed by Yaesu (FTDX101D) and Elecraft (K4). The reason is evident: Good mixers are still better (and scale better) than state of the art ADCs. I think our Polyphase Harmonic Rejection mixer-based SDR architecture is a step in the right direction, where both goals are achieved without compromises, and in the most economical way. The first version was kind of a revolution for us, but the “Discovery” is the consolidation of a lot of polishing opportunities we discovered since the first release.

Thank you for the details, Youssef–it sounds like a lot of innovation and iterative upgrades have gone into the Discovery receiver design.

Of course, I will plan to grab the HF+ Discovery and review it here on the SWLing Post. In the meantime, check out the excellent RTL-SDR website where Carl has posted a short preliminary review of a pre-production HF+ Discovery.

Click here to check out the HF+ Discovery at Airspy and place a pre-order ($169 US). 

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RSGB 2018 Convention Lecture: DC to Microwaves on your smartphone

(Source: Southgate ARC)

The presentation by Noel Matthews G8GTZ on the Farnham WebSDR given to the 2018 RSGB Convention is now available on YouTube:

Click here to view on YouTube.

This presentation gives an overview of the Farnham WebSDR, available at http://farnham-sdr.com/ which currently covers the LF bands through to 10GHz.

The presentation describes the system architecture and antennas currently used on each band and how the team has used RTL dongle receivers, available for under £10, to give good RF performance on all bands from DC to 10GHz. There is a demonstration of the SDR in use on both PC and smartphone.

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The Hermes-Lite SDR: an open source HF transceiver based on a broadband modem chip

Many thanks to SWLing Post contributor, Pete Eaton, who writes:

Don’t know if you are familiar with this project, a full blown 5 watt HF SDR Transceiver for less than $300!

No sound cards, DUC/DDC architecture.

Here’s the project description by Steve Haynal via YouTube:

The Hermes-Lite is a low-cost direct down/up conversion software defined amateur radio HF transceiver based on a broadband modem chip and the Hermes SDR project. It is entirely open source and open hardware, including the tools used for design and fabrication files. Over 100 Hermes-Lite 2.0 units have been successfully built.

The FOSSi Foundation is proud to announce Latch-Up, a conference dedicated to free and open source silicon to be held over the weekend of May 4th and 5th in Portland, Oregon, USA. Latch-Up: a weekend of presentations and networking for the open source digital design community, much like its European sister conference ORConf. Produced by NDV.

Click here to view this presentation on YouTube.

Fascinating! Thank you for sharing, Pete!

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The NSA’s Software Defined Radio application “RedHawk” is now open source

Many thanks to SWLing Post contributor, Andrew, who writes:

Not kidding, a friend told me that NSA released a bunch of software to open source, the main list being here:


While looking at the list of projects on that page, halfway down the page, I found a project called “RedHawk” which is described as:

“A software-defined radio (SDR) framework designed to support the development, deployment, and management of real-time software radio applications.”

Now, being curious I opened the github link:


[It] contains quite a number of subprojects, modules and other stuff, then I checked the main “RedHawk” project:


Here’s the documentation:


It seems really interesting; apparently it allows to define a wealth of processing stages (e.g. filters, converters…) and connect them to process signals coming from an SDR; I think it may be a very interesting and useful tool to fiddle/experiment with SDR receivers, if I’m not wrong it may allow to push an SDR to the limits, improving its performance, and may also be useful to write SDR software!

Fascinating! Thank you for the tip, Andrew!

Post Readers: It appears this project has been in the public domain for a little while. Please comment if you’ve tried implementing RedHawk in your SDR system!

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