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.
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OpenFest 2014: Software Defined Radio and RTL-SDR by Harald Welte

Recently some talks from the OpenFest 2014 conference have been uploaded to YouTube. One of the talks uploaded is titled “Software Defined Radio and RTL-SDR” and is by Harald Welte. Although a couple of years old, the talk is still valid and quite clearly explains some concepts about how software defined radio works, and then goes on to talk about the RTL-SDR dongle and some of it’s applications. The introduction reads:

This talk is about getting started with the basics of software defined radio (SDR). It introduces the fundamental concept of SDR constrasting classic radio systems, and continue to cover the rtl-sdr project, a software/driver architecture for the ultra-cheap RTL2832U based hardware. There will be practical demonstration using some of the readily-available Open Source projects implementing receivers for various radio systems.

If you are interested in his talk, then his slides appear to have been uploaded here.

Software Defined Radio and rtl-sdr - Harald Welte

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Software De-Dispersion of RTL-SDR Pulsar Data

Back in September 2015 we posted about how radio astronomers Peter W East and GM Gancio were able to use an RTL-SDR dongle for the radio astronomy task of detecting pulsars. A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish antenna and a radio, like the RTL-SDR. 

More recently they published a new paper titled “Software De-Dispersion of RTL-SDR Pulsar Data” (pdf).  De-dispersion is a technique that allows very weak signals to be extracted from the background noise. The introduction to the paper reads:

Data files produced by RTL SDR dongles can be folded directly for pulsar detection using software such as rapulsar.exe. Using simple I/Q vector averaging software, the data can be down-sampled by factors of more than 100 prior to folding and/or period search processing to speed up useful data extraction. Ideally, wide band RF data should be de-dispersed to optimise later search and folding processing. De-dispersion is normally carried out by time adjusting data sampled from RF filter banks before combination. This note describes how data already digitised from the RTL SDR can be spectrum analysed or filtered using the FFT algorithm. Two methods are discussed, one summing power with some down-sampling; the second, a ‘coherent’ method that de-disperses the rtlsdr.exe .bin data file and outputs a .bin-compatible file. Both accurately de-disperses the data offering an improved folded data SNR.

More information about radio astronomy with the RTL-SDR, pulsars and the associated software links can be found at Peter W East’s webpage http://y1pwe.co.uk/RAProgs/index.html.

The de-dispersion principle
The de-dispersion principle
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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

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Using an RTL-SDR to help Build Dynamic Spectrum Access Prototypes + DARPA Spectrum Collaboration Grand Challenge

Over on YouTube user Andre Puschmann has uploaded video showing his experiments with implementing dynamic spectrum access. Dynamic spectrum access is a upcoming technology that will allow the frequency spectrum to be more easily shared between many users. An IEEE paper describes Dynamic Spectrum Access in the following paragraph

Dynamic spectrum access is a new spectrum sharing paradigm that allows secondary users to access the abundant spectrum holes or white spaces in the licensed spectrum bands. DSA is a promising technology to alleviate the spectrum scarcity problem and increase spectrum utilization.

In his experiments Andre uses USRP and bladeRF software defined radios as the transmit radios, and an RTL-SDR as the receive radio. His video shows a video stream being received by the RTL-SDR which is not impacted by any spectrum frequency switches.

Building Dynamic Spectrum Access Prototypes using Open-Source SDR Software

In addition to this, DARPA has recently announced a new Grand Challenge that will focus on Spectrum Collaboration. We would expect SDR’s to be heavily used in this type of challenge. Their press release writes:

DARPA today announced the newest of its Grand Challenges, one designed to ensure that the exponentially growing number of military and civilian wireless devices will have full access to the increasingly crowded electromagnetic spectrum. The agency’s Spectrum Collaboration Challenge (SC2) will reward teams for developing smart systems that collaboratively, rather than competitively, adapt in real time to today’s fast-changing, congested spectrum environment—redefining the conventional spectrum management roles of humans and machines in order to maximize the flow of radio frequency (RF) signals. DARPA officials unveiled the new Challenge before some 8000 engineers and communications professionals gathered in Las Vegas at the International Wireless Communications Expo (IWCE).

The primary goal of SC2 is to imbue radios with advanced machine-learning capabilities so they can collectively develop strategies that optimize use of the wireless spectrum in ways not possible with today’s intrinsically inefficient approach of pre-allocating exclusive access to designated frequencies. The challenge is expected to both take advantage of recent significant progress in the fields of artificial intelligence and machine learning and also spur new developments in those research domains, with potential applications in other fields where collaborative decision-making is critical.

USA Frequency Allocations
USA Frequency Allocations

 

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Videos Showing Rpidatv in action

A few days ago we posted about the release of Rpidatv, a program that allows a Rapberry Pi to transmit DATV without the need for any additional hardware. DATV stands for Digital Amateur TV, and can be received with an RTL-SDR using a program called leandvb.

Over on YouTube, the programmer of Rpidatv (Evariste F5OEO) has uploaded a video that shows a Rpidatv + leandvb system in action. The video demonstrates the touch screen GUI which can be used if a touch capable LCD screen is connected to the Raspberry Pi. It also shows the whole system in action with a video being transmitted from the Raspberry Pi camera to a Linux PC with an RTL-SDR running leandvb.

rpidatv with leandvb

Another video uploaded to YouTube by Qyonek also shows Rpidatv + leandvb in action.

Testy rpidatv + leandvb

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A review of the Soft66RTL3 RTL-SDR + Upconverter + RF Amp Combination Circuit

Over on the SWLing Post blog contributor Mike Ladd has posted up a review of the Soft66RTL3 software defined radio. The Soft66RTL3 is a fully enclosed SDR unit that consists of a standard mini RTL-SDR dongle, a selectable upconverter circuit, several switchable bandpass filters for HF and a UPC1688 RF amp which is enabled in HF mode and is controllable through a trimmer pot. The selectable bandpass filters are from 0.4 MHz to 1.2 MHz, 1.2 MHz to 5 MHz, 5 MHz to 15 MHz and 15 MHz to 30 MHz. The unit also comes enclosed in an aluminum box with an SMA input connector and Micro-B USB port.

The Soft66RTL3 is custom produced by Kazunori Miura (JA7TDO) who is based in Japan. The Soft66RTL3 sells for $40 USD shipped, or $46 USD shipped with registered air mail. 

In the review Mike shows us the insides of the Soft66RTL3 and discusses its features. Later he also shows an installation and user guide.

The Soft66RTL3 Unit
The Soft66RTL3 Unit
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RTLSDR4Everyone: ADS-B Bias-T Filter and External amplification

Akos from the RTLSDR4Everyone blog has recently come out with a new post where he explains how to get the best ADS-B reception with an LNA and filter. In his experiments he uses an LNA4ALL low noise amplifier and and ADS-B Filter, both of which are sold by Adam 9A4QV. New versions of the filter sold by Adam now also include a built in bias-tee circuit which allows you to easily power the LNA4ALL over the coax cable, allowing you to place it externally.

In the post Akos shows where to optimally place the LNA and how you can use your Raspberry Pi together with the ADS-B filter with bias-T in order to power an antenna mounted LNA4ALL. The post also discusses what the cheapest solution is for European customers attempting to optimize their ADS-B reception.

ADS-B Setup including a filter, bias tee, LNA and Raspberry Pi.
ADS-B Setup including a filter, bias tee, LNA and Raspberry Pi.
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