Category Archives: Software Defined Radio

Hamvention Highlights: Affordable diversity reception with the SDRplay RSPduo

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

Diversity reception with the SDRplay RSPduo

Last year, during the 2018 Hamvention, SDRplay announced the RSPduo, a 14bit dual-tuner SDR. We posted a review of the RSPduo on the SWLing Post.

At the time, SDRplay mentioned that the RSPduo could eventually be used for diversity reception.

Diversity reception is the ability to combine or select two signals, from two (or more) antenna sources, that have been modulated with identical information-bearing signals, but which may vary in their fading/noise characteristics at any given instant.

In short, diversity reception gives one a powerful tool to mitigate fading and noise, and to improve a signal’s overall integrity.

Andy and Mike with SDRplay demonstrated SDRuno’s diversity reception functionality and noted that it will soon roll out as a free upgrade to SDRuno, SDRplay’s open SDR application.

I should note here that the SDRplay booth at the 2019 Hamvention was incredibly busy—no doubt, because the RSPduo must be one of the least expensive, most accessible, ways to experiment with diversity reception. Case in point: the new Elecraft K4D transceiver will support diversity reception, but the price is about $4,700 US; the RSPduo can be purchased for $280 US.

Based on the demonstration, this feature will be quite easy to use and I love how it has been implemented in the SDRuno GUI (graphical user interface).

To learn more about the RSPduo, check out SDRplay’s website or read our review. Of course, when SDRplay releases the diversity reception upgrade to SDRuno, we will make an announcement!

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

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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

Elecraft introduces the K4 high-performance direct-sampling SDR

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Click to enlarge (Source: K4 Product Brochure)

Today we learned about the latest addition to the Elecraft product line, the Elecraft K4.

This fills a niche in the Elecraft product line and is certain to directly compete with the likes of the Icom IC-7610 and a number of Flex Radio transceivers, among others.

Elecraft describes the K4 as having a “modular hybrid architecture”. Below, I’ve pulled the text and images from the Elecraft product brochure.

Wayne Burdick (N6KR) of Elecraft notes that tomorrow (Friday, May 17, 2019) the Elecraft site will (re)launch a K4 product page with pre-order/reservation page.

I plan to learn more about the K4 and report back during Hamvention this week. Stay tuned by bookmarking the tag Elecraft K4:

Elecraft K4 Product Information

(Source: Elecraft K4 Product Information Sheet via Lutz Electronics, Switzerland)

Click to enlarge (Source: K4 Product Brochure)

A direct-sampling SDR you’ll love to use

Our new K4 harnesses the latest in signal processing while retaining the best
aspects of the K3S and P3. The resulting user interface makes the technology
transparent, allowing you to focus on working the world.

160-6 meter, all-mode coverage & dual RX

The K4 includes dual receive over 100 kHz to 54 MHz. Since it utilizes direct
sampling, there’s no need for crystal filters in the K4 or K4D (see Models, back
page). For extreme-signal environments, we offer a dual superhet module
(standard in the K4HD). An internal VHF/UHF module is also planned.

High-resolution mini-pan for each receiver

Our advanced fine-tuning aid, with its resampled bandwidth as narrow as +/- 1
kHz, is displayed separately from the main panadapter. You can turn it on by
tapping either receiver’s S-meter or by tapping on a signal of interest.

Simple operation and setup

The K4 features a large, full-color touch display, combined with a rich set of real
controls. Per-VFO transmit metering makes split mode completely foolproof.
Band-stacking switches and per-receiver controls are both intuitive and versatile,
adapting to operating context. Usage information on these and other features
is just one tap away, thanks to our built-in help system.

Click to enlarge (Source: K4 Product Brochure)

Rich I/O complement

The rear panel includes all the RF, analog and digital I/O you’ll need to complete
your station. All K-line accessories are supported, including amps, ATUs, and our
K-Pod station controller. The HDMI video output supports an external display
with its own user-specified format.

Full remote control from multiple devices

The K4 can be 100% remote controlled, via Ethernet, from a second K4 as well as
a PC, notebook, or tablet. Panadapter data is included on all remote displays.

Modular hybrid architecture

The K4 adapts to your needs, with three models to choose from:

Basic K4 with wide-range dual receive
K4D with diversity receive
K4HD with a dual superhet module for exceptional dynamic range

You can upgrade or add options as desired, or as new technology becomes
available. This extensibility applies to software as well. The K4’s powerful, fast-starting CPU provides unlimited expansion opportunities.

Fast signal processing

The RF signal chain in the K4 incorporates parallel hardware processing of data
streams, including a dedicated DSP subsystem. This, combined with silent,
PIN-diode T/R switching, ensures fast CW break-in. Data and speech-processing
delays are also minimized.
Standard DSP features include easy-to-adjust, per-mode RX/TX EQ; clean,
punchy RF speech processing; full DVR capabilities; and several built-in data
decode/encode modes. Direct-sampling technology results in an ultra-flat
passband response for clean RX and TX audio. Since the signal chain is softwaredefined, the DSP can be field upgraded to add new algorithms and operating
modes.

KAT4 ATU

The KAT4 ATU has a nominally 10:1 matching range. It includes 3 antenna jacks,
any one of which can be selected as an input for one or both receivers.

Internal VHF/UHF module (future option)

An expansion slot is reserved for a high-performance VHF/UHF module, with
output of approximately 15 W. This module will support all modes.

Kit version

A no-soldering kit version of the K4 is planned for later release. Builders will learn
about advanced radio technology as they proceed. All modules are pre-aligned
and tested.

K4 Key Specs and Features

Size: 4.5”Hx13.5”W,10”D
Weight: Approx.10lbs
SupplyVoltage: 12-15VDC
Current: ~2ARX,~18-23ATX
FrequencyRange: 100kHz-54MHz(VHF/UHFrangetobe determined*)
Stablility: +/-0.25ppm(TCXO) Modes: CW, SSB, AM, FM, Data
LCD: 7”color;touch&mousecontrol Text modes: CW, PSK31/63, RTTY KAT4ATU:
10:1+range;3ant.jacks RXantennasources: Upto5
A-to-D Converter(s): 16 bits
I/O: USB-Ax3,USB-B(twovirtualcomports+audio),RS232(DE9), Ethernet, HDMI. front/rear mic, front/rear phones, LINE in/out, speakers,PTTin,KEYout,paddle,key, ACC,12Vout.
CWQSK: Silent,PIN-diodeswitched
Other: RX/TX EQ, real-time clock,100% remote control including panadapter data, remote antenna switch control*, custom in-box software apps*

Models (K4 & K4D upgradeable by the user at any time)

K4: Basic K4 transceiver provides 160-6 m, all-mode coverage; 100 W output; five receive RF sources; and wideband dual watch, allowing the main and sub receivers to be set for the same or different bands.
K4D: Adds KDIV4 option, with a second set of band-pass filters and additional direct- sampling ADC module. This allows the two receivers to use different antennas – a requirement for diversity receive. Having two sets of band-pass filters also optimizes signal handling when the receivers are on different bands and/or antennas.
K4HD: Includes all of the above, plus our dual superhet module, the KHDR4. Ideal for competitive field day, contesting, and DXpedition stations. Each superhet receive section includes two crystal filters: one SSB/data bandwidth, one CW bandwidth. The superhet’s 8 MHz IF has excellent dynamic range, so additional crystal filters are not required.

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

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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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SDRplay RSP1A Metal Case Upgrade in-stock again

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A number of SWLing Post readers have asked about the metal case upgrade for the SDRplay RSP1A. It has been out-of-stock for several months. I just learned via Mike Ladd on Facebook, that the case is back in stock and shipping via eBay. He also noted that it will soon be available via Amazon.com. The price is $24.95 shipped via eBay.

Click here to view on eBay.

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Dave’s updated SDRplay RSP1A review

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Many thanks to SWLing Post contributor, Dave Zantow (N9EWO), who writes:

Our greatly “Updated” SDRplay RSP1A review is now available (with new number two 2019 manufactured test sample). As usual with our web pages be sure and have pop up blocker on full (allow no pop ups) and browser security settings at default or above.

http://n9ewo.angelfire.com/sdrplay.html

Thanks for sharing this, Dave!

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