Category: Other

LuaRadio: New Flowgraph Based Digital Signal Processing Framework for SDR

LuaRadio is a new Digital Signal Processing (DSP) framework for software defined radios such as the RTL-SDR. It is similar to GNU Radio in that the flowgraph is composed of graphical blocks that can be visually connected to one another in an editor. However compared to GNURadio it aims to be very lightweight in terms of disk space used (1 MB footprint) and the number of dependencies required (zero dependencies required unless you need real time highly optimized libraries). It is also written purely in the Lua programming language. The authors of LuaRadio write “LuaRadio is more inclined towards scripting and prototyping than GNU Radio, and emphasizes fast block development.”

On their website there are already several example application flowgraphs uploaded, such as decoders for WBFM Mono/Stereo, NBFM, AX.25, POCSAG, RDS, AM and SSB. Looking and building such flowgraphs is extremely helpful for learning DSP, and DSP languages like this are excellent for prototyping new signal decoders. In addition, if you are new to SDR they also have a very useful page that explains basic SDR and radio concepts.

A LuaRadio based POCSAG decoder flowgraph.
A LuaRadio based POCSAG decoder flowgraph.

Cyberspectrum #16: Software Defined Radio Meetup

Every month SDR evangelist Balint Seeber hosts the Cyberspectrum Meetup in San Francisco, where many SDR fans come together to listen to various presentations. This months meetup is due to be held on June 29 at 7 PM (San Fran time, about 18 hours from the time of this post). If you are in San Francisco you can attend the live meetup, but if not you can watch the live stream on YouTube.

This time the talks include:

• “Understanding the LTE Physical Layer” with Sandor Szilvasi (@sszilvasi)

LTE is an incredible, yet complex, cellular networking standard. Sandor will break it down and explain how a LTE signal is constructed. He will also live demo the demodulation and decoding of local carriers.

LTE_cyberspectrum

• “Interactive Install & Setup-fest” with the group

We would like to open up the forum to those who wish to get set up with SDR (hardware and/or software). Bring along your equipment, and as a group we can look at/debug the steps required to get you up and running. This could also include setting up an app, or fixing an Out-Of-Tree module, or even an environment issue on your laptop.

• “GNU Radio Tutorial Part 2” with Neel Pandeya

The tutorial series will continue! This time we will look at how to construct an FM radio receiver, and decode the RDS digital subcarrier. This will include:

• Explain concepts behind commercial FM and RDS
• Receiving mono FM using a from-scratch flowgraph
• Showing how to build ‘gr-rds’
• Demonstrate stereo FM+RDS reception using ‘gr-rds’
• Building GQRX
• Demonstrate FM reception using GQRX

50 Units of a $199 Nuand bladeRF x40 for Sale: 1-Day Only

Nuand is the company responsible for the bladeRF software defined radio. The bladeRF x40 is a SDR that usually costs $420. It uses a LimeMicro LMS6002D chip, which has a 12-bit ADC and a tuning range of 300MHz – 3.8GHz.

For one day only they have released a special price for the bladeRF x40 of $199 USD, for the first 50 customers only. At the time of this post the deal still seems to be active, and the coupon code of “MHZ” is still working. Of note is that the recently successfully crowdfunded LimeSDR uses the newer and better LimeMicro LMS7002M chip, so Nuand may be testing the waters for a lower price point on their bladeRF. However, one thing to note is that the bladeRF is proven hardware with active software applications, whereas the LimeSDR is not yet proven. 

Nuand also recently released an update which saw the source released for an ADS-B decoder that can be run on the bladeRF’s onboard FPGA, and also an update which allows the bladeRF to display up to 124 MHz of bandwidth at any one time. The large bandwidth display appears to work in a similar way to rtl_power or SpectrumSpy for the Airspy, by quickly switching between multiple chunks of frequency. The difference is that the bladeRF can do this by using onboard HDL accelerators which allow it retune extremely fast at several thousand times a second.

bladeRF displaying 96 MHz.
bladeRF displaying 96 MHz.

First tests of the LimeSDR with GQRX

The LimeSDR is a new SDR $299 USD currently seeking crowdfunding over on CrowdSupply. At the time of this post the LimeSDR is currently 60% funded, with 29 days left to go. The LimeSDR is a RX/TX capable device, with a 100 kHz – 3.8 GHz frequency range, 12-bit ADC and 61.44 MHz bandwidth. From the price and specs, we consider it to be a potential next generation HackRF type device which will have vastly improved RX performance.

Over on the MyriadRF blog, Alexandru Csete has received a demonstration unit, and has written about his first thoughts on the LimeSDR. Alexandru was able to easily set the device up by using SoapySDR and GQRX on Linux. He first did the “hello world” of SDR and was able to successfully receive broadcast FM signals. Next he tried to receive Amateur Satellite signals and was successful in receiving the FO-29 satellite. Finally he was also successful in receiving NOAA weather satellite images.

From a quick judge of the waterfall images it looks as though the LimeSDR has a very clean spectrum with a low noise floor, which looks good for RX. In future posts Alexandru hopes to test out the transmit capabilties of the LimeSDR, as well as its shortwave RX performance.

LimeSDR receiving the FO-29 satellite on GQRX.
LimeSDR receiving the FO-29 satellite on GQRX.

Building a Tuning Knob for SDR#

If you love using SDR’s on the PC but miss the old feeling of tuning the frequency with a knob then 19max63 has a solution for you. On his blog he’s posted about how he built his own tuning knob by using a USB mouse PCB circuit and replacing the mouse wheel with a rotary encoder with no detents. Detents are the little clicks or steps that you can feel in some knobs, but for accurate frequency tuning you don’t want those.

His post shows the exact parts he bought (knob, mouse, buttons), the mods he made to the knob and mouse PCB, and how he put it all together. He writes that parts can all be found cheaply on eBay or Aliexpress and the total cost to produce a single knob was only about $4 (though he had to buy some parts in lots of 5 to 10).

The finished tuning kob for RTL-SDR and SDR#.
The finished tuning kob for RTL-SDR and SDR#.

KiwiSDR Kickstarter Successfully Funded

Last month KiwiSDR started their fundraising campaign on Kickstarter. The kickstarter has now completed. The goal was to raise $50,000 USD and they have well surpassed that mark by reaching $70,757 USD. If you missed out on the Kickstarter then it is still possible to preorder by directly emailing the KiwiSDR team.

The KiwiSDR is a software defined radio with 30 MHz of bandwidth and a tuning range that covers 0 – 30 MHz (VLF to HF). It is intended to be a low cost web based SDR that can be accessed from all over the world via a browser interface. It is designed as a cape for the BeagleBone Black mini embedded computer, and uses a LTC 14-bit 65 MHz ADC and Xilinx Artix-7 A35 FPGA. It also has an integrated SDR based GPS receiver which is used to automatically compensate for any frequency drift from the main 66.6 MHz oscillator. It runs on the OpenwebRX web based software, which many RTL-SDR users have already been using to stream live radio to the web.

Right now the team is beta testing some sample boards and appears to be getting ready for the large production run.

In a previous post we mentioned that the KiwiSDR project had some ethical issues attached to it. The creator of the OpenWebRX software, Andreas, was upset over the fact that the KiwiSDR had forked his open source project and had said that they would not share any profits. However, it appears that KiwiSDR have now struck a deal with Andreas, with both sides being happy, thus resolving any ethical issues.

The latest KiwiSDR Board
The latest KiwiSDR Board

Massdrop: Group Software Defined Radio Purchasing

Over on the r/rtlsdr subreddit forum many users are attempting to combine their purchasing power to initiate a ‘massdrop’ for a higher end software defined radio. Massdrop is a service that allows for large group purchases to be made. When a large group comes together to buy the same product the product manufacturer will often be able to offer better wholesale prices due to the increased sales volume.

The Massdrop service also allows for the group to vote on the most desired product. Currently the group is voting for several SDR’s including the SDRplay, HackRF, BladeRF, Airspy, USRP, Red Pitaya, Apache Labs and Perseus SDRs. Currently winning the vote at the time of this post going live is the SDRplay, with the HackRF coming in a close second. Once 200 total votes are reached a representative from Massdrop will contact the manufacturer of the most desired SDR and try to work out a deal for the group buy. There are 147 total votes at the moment, so they are almost at the threshold of being able to initiate negotiations.

If you want to take part in the Massdrop sign up to their website at www.massdrop.com and then visit the SDR voting link at https://www.massdrop.com/vote/Software-Defined-Radios1 (you must be logged in to see the SDR voting page).

If you’re interested in learning more about these higher end radios then we have a list of several SDR’s available here, and a review of the Airspy, SDRplay and HackRF here.

Current voting at the time of posting for the Massdrop.
Current voting at the time of this post for the Massdrop.

New Book out by the Author of the RTLSDR4Everyone Blog

Akos, the author of the rtlsdr4everyone blog has recently released a new Kindle book on Amazon which sells for $5 USD. It is titled “RTL-SDR for Everyone: Second Edition 2016 Guide including Raspberry Pi 2”. Akos writes that the book is intended for beginners and anyone wishing to maximise their RTL-SDR dongle’s performance. The blurb reads:

Chapters cover all you need to know for the best reception with $10 RTL-SDR dongles. Wideband and specialist antennas, modding and noise reduction tips aided with images and diagrams.

My blog at http://rtlsdr4everyone.blogspot.com is only a fraction of the know-how in this book – if you want to take performance to the next level, or simply have no time to waste searching for information on the Internet, then this book is for you.

Readable on all platforms: Windows and Mac, Android and iPad, iPhone and Ipod touch.

Chapter 1 begins with Akos explaining some of the theory and jargon used in the radio world. Chapter 2 of the book talks about the hardware such as the RTL-SDR dongles, coax cabling, connectors and preamplifiers. Chapter 3 talks about the software and includes installation guides for programs like SDRsharp, SDRConsole, Virtual Audio Cable, as well as tutorials for receiving signals such as weather satellites and ADS-B. Chapter 4 goes on to talk about the different types of antennas and Chapter 5 discusses how to maximise the performance of the RTL-SDR. Finally Chapter 6 discusses the Raspberry Pi and it’s links to the RTL-SDR.

A preview of the first few pages in the book is available on Amazon and remember that there is no risk with buying Kindle books as they can easily be fully refunded within the first seven days of purchase.

rtlsdr4everyone_book