The FlightAware ProStick Plus is an modified RTL-SDR designed specifically for ADS-B reception. Its main defining feature is that it has a built in low noise figure LNA, and a 1090 MHz SAW filter. The LNA reduces the noise figure of the RTL-SDR, improving ADS-B reception and thus increasing the number of messages received and the receivable range of aircraft. The SAW filter helps remove out of band signals which can cause the RTL-SDR to overload if they are particularly strong. The Prostick Plus also comes with a TCXO, and SMA connector.
If you are mainly interested in ADS-B reception, or are looking to set up an ADS-B station then the Prostick Plus is one of the best choices you can make. See our previous review here.
We are now reselling some of FlightAware’s Prostick Plus dongles in our store now. They cost $24.95 USD including free shipping worldwide. We intend to sell them mainly to customers outside of the USA, as FlightAware already sell them officially on Amazon, but we offer free shipping anywhere in the world.
About a month ago the Airspy and SDRSharp development team released their new ‘SpyServer’ software. SpyServer is a streaming server for Airspy devices, which allows them to be used over a network connection. It is somewhat similar to rtl_tcp which is familiar to RTL-SDR users, although unlike rtl_tcp, SpyServer uses a multiclient architecture which allows several clients to connect to the server at the same time with each being able to choose individual bandwidth settings.
Today SpyServer was updated (changelog), and it now also supports the RTL-SDR dongle. The software can be found in the latest version of SDR# from www.airspy.com. The Airspy download contains the SpyServer for Windows and Linux, and the Raspberry Pi and Odroid server is available here.
To use SpyServer with the RTL-SDR you’ll first need to edit the “spyserver.config” file which is in the SDR# folder. Open this file with a text editor like Notepad, and set the “device_type” to “RTL-SDR”. Now you can run spyserver.exe on your server and it will use your RTL-SDR. Multiple dongles can be used by editing the “device_serial” string in the config file. Next on the client PC run the latest version of SDR#, and choose the Source as “Spy Server”. Here you can enter your networked PC’s IP address to connect to it.
We tested the updated SpyServer with an RTL-SDR dongle and it worked perfectly. On an 802.11n WiFi connection we were able to stream up to 1 MSPS without problems. 2 MSPS was a bit jittery, but on an Ethernet or 802.11ac WiFi connection it should work with no problems. We also tested connecting two PC’s to a single SpyServer and both were able to run at the same time without trouble. The client which connects first gets to keep control of the center frequency and gain, whilst the second client has those options locked.
Back in August of 2016 we posted about Lukas Lao Beyer’s work in creating a software defined radio from scratch. His goal was to design something that fit somewhere in between the $300 HackRF and the higher end and more pricey USRP radios. Back then he had completed the design and had a working prototype.
Now the Lukas has put the FreeSRP up on CrowdSupply, a crowd funding website. The FreeSRP is priced at $420 each and the goal is to raise $75,000 in order to begin a manufacturing run of the SDR. At the time of writing this post, the campaign has been running for a day at is already 8% funded.
The FreeSRP has a tuning range from 70 MHz to 6 GHz, uses a 12-bit ADC with a sampling rate of up to 61.44 MSPS, and has a maximum analog filter bandwidth of 56 MHz. It is a full-duplex radio (can transmit & receive at the same time). The main chip in the unit is the fairly expensive (~$150 USD) AD9364 integrated RF transceiver chip and it also comes with a Xilinx Artix 7 FPGA. Furthermore the hardware and code is entirely open source.
The specs seem somewhat similar to the cheaper LimeSDR, although the main chipset is different as the FreeSRP uses the AD9364 chip and the LimeSDR uses their own LimeMicro LMS7002M chip. The AD9364 is the same chip used in the USRP B200 units. Below is an in-class comparison given on the FreeSRP CrowdSupply page.
Yesterday Mike (ghostop14) submitted to us by email a document that gives an overview of his experiments on rewriting several GNU Radio blocks to take advantage of OpenCL GPU acceleration. High end discrete gaming GPU’s (Graphics Processing Unit) on PC’s are a very powerful parallel processors which can be significantly faster at performing calculations than the general purpose CPU. But only algorithms that can be parallelized are worth running on the GPU, and there is an additional overhead to pass the data between the CPU and GPU. This means that only some algorithms will actually work faster on the GPU. GPU acceleration could be part of the key to allowing very high bandwidth SDRs to run on PC’s.
In Mike’s experiments he accordingly found that only some GNU Radio blocks could be accelerated by the GPU. Many blocks ran more slowly on the GPU due to the additional overheads. In the end the blocks he tested that showed actual or at least mixed acceleration were:
Log10
Complex To Arg
Complex To Mag/Phase
A custom Signal To Noise Ratio Helper that executes a divide->Log10->Abs sequence
Mag/Phase To Complex (OpenCL performed better only for blocks above 8K for the 1070, and 18K for the 970 and 1000M)
Signal Source (OpenCL outperformed CPU only for the 1070 for 8K blocks and above)
Quadrature Demodulation (OpenCL performed better only for blocks above 10K)
The project is called gr-clenabled, and the open source code for gr-clenabled is available over on GitHub. A document documenting a full study of the implementation and performance of GPU GNU Radio blocks can be found here. Below is an excerpt from Mike’s overview document (if you want more information we suggest reading the overview first, and then the full study document):
About 4 months ago I decided to take on a project that I had wished existed for some time. With all of the code available for using graphics cards for signal processing why were there not a wealth of GPU-accelerated blocks for GNURadio? Really leveraging my new graphics card (an NVIDIA GTX 1070), couldn’t I drive 80 MSPS or higher through if I had hardware that could supply it? (I know USB 2.0 bus speeds, some decoders require hardware for speed, etc. but an SDR enthusiast can still dream)
My idea seemed simple enough. Why not develop OpenCL versions of the most common blocks used in digital data processing? I may not hit my throughput goal but I bet I can really accelerate my flowgraphs. And since I can dream up whatever I want before I have to actually make it, why not make it even more scalable? Why not be able to take full advantage of multiple graphics cards in a system by being able to assign different blocks to run on different cards?
I know, that’s a lot of questions, but sounds great if it existed right? What I didn’t realize was the scope of the box I was about to open. My first task at hand was to learn OpenCL and REALLY dig into the depths of the GNURadio code. Turns out not all signal processing algorithms lend themselves nicely to the way massively parallel processing works. And there’s a time price to pay to move data to a PCI card for processing then retrieve the results that has to be considered. Some native blocks take longer than this transfer time to run and can benefit from offloading, while others are so fast they’re done before a GPU even gets the data. But I’m getting ahead of myself here.
Throughput of the log10 GNU Radio block on various different GPU’s at different block sizes.
The KiwiSDR is a wideband HF software defined radio that is designed to receive the entire 10 kHz – 30 MHz spectrum all at once. It works together with a BeagleBone single board computer and uploads it’s wideband radio data to the internet via the OpenWebRX SDR web interface and control software. Examples of KiwiSDRs shared publicly on the web with OpenWebRX can be found at sdr.hu.
Back in April of last year the KiwiSDR was successfully crowd funded on Kickstarter, and was later released for general ordering in October from SeeedStudio. Normally the KiwiSDR kit including KiwiSDR, BeagleBone, enclsoure, GPS antenna and SD card costs $299 USD.
Currently a Massdrop is underway for KiwiSDR (it seems that the link only works for logged in users). If you didn’t already know, a Massdrop is an organized group buy effort. Buy grouping several individual orders together and making a bulk order, the manufacturer is likely to give a discount. Currently the price for the KiwiSDR kit on the Massdrop is $249.99 USD ($50 saving on the regular price), with only 2 days remaining to join in. Once finished, the estimated shipping date is April 24, 2017.
Over on YouTube Jon, head of SDRplay marketing has uploaded a video showing how the SDRplay RSP2 can be used for accurate RF power measurements. In the video he shows how well calibrated the RSP2 is by comparing how well the power measurements in SDRuno match with a signal generator at various frequencies and power levels.
Later in the video he shows how RF power measurements can be used in a field situation by using the RSP2 and SDRuno to compare the performance of two different whip antennas.
Last month we saw news of the Airspy HF+, which is a yet to be released software defined radio with a focus on high performance reception in the HF bands. Some preliminary specs were unofficially released back then on the Airspy Yahoo forums.
Now over on the Airspy website, the official specifications have been released and they are pasted below. The specs suggest that the Airspy HF+ will have extremely high performance when it comes to strong signal handling. This means that there should be little to no chance of overloading, and thus no intermodulation or spurs.
The goal pricing is to be below $200 USD. If this is true, then it will compete heavily with the $249.95 USD ColibriNANO which is another new HF specialty radio with similar specs.
The Airspy team write:
Airspy HF+ is a paradigm shift in high performance HF radio design. It is a joint effort between Airspy, Itead Studio and some famous chip maker to build a state of the art SDR for HF and VHF bands.
Like most high-end HF receivers, the HF+ uses very high dynamic range ADC’s and front-ends. But unlike the current offerings in the market, it also brings more frequency agility by using high performance passive mixers with an excellent overtone rejection structure. Both the architecture and level of integration achieved in this design allow us to bring top performance reception at a very affordable price.
HF Tuner
Airspy HF+ achieves excellent HF performance by mean of a low-loss band filter, a high linearity LNA, a high linearity tunable RF filter, an over-tone-rejection (OTR) mixer that rejects up to the 21st harmonic and an IF filter. The 6 dB-stepped AGC gain is fully controlled by the software running onto the DSP which optimizes the gain distribution in real time for optimal sensitivity and linearity. OTR is a key issue in wide band HF receivers because of the large input signal bandwidth. The output of the IF-filter is then digitalized by the IF ADC for further signal processing.
VHF Tuners
Excellent VHF performance is also achieved by using optimized signal paths composed by band filters, high linearity LNAs with a stepped AGC and an over-tone-rejection mixer and IF filters optimized for their respective bands. The amplifier gain is switchable in 3 dB-steps and is fully controlled by the AGC processing running onto the DSP. The RF signal is converted to baseband by a high linearity passive mixer with overtone-rejection structure. The low-IF signal is then converted into the digital domain by the IF ADC for further digital signal processing.
IF Digitalization
The IF digital to analog converter has a 4th order multi-bit topology; it features very high dynamic range and linearity. The IF-ADC sampling frequency is determined by a control algorithm running on the DSP. This advanced technique changes the sampling frequency depending on the tuning frequency with the goal of avoiding the disturbances generated by the switching discrete-time sections of the IF-ADC.
Digital Down Converter
Once the IF signal is digitalized, the high sample rate I/Q stream is then frequency translated and processed with cascaded CIC and FIR decimation stages. After every stage, the sample rate is reduced and more the resolution is increased. The final signal at the output has 18bit resolution and the alias rejection performance is 108 dBc. The data is then scaled to 16bit and sent to the Micro-Controller for streaming over USB.
Use it over the network!
Connect as many SDR applications as needed to the HF+, over the Internet or in your own local network with near zero latency thanks to the new SPY Server software. This setup basically brings all the flexibility of Web based SDRs while still benefiting from the full power of desktop applications. The IQ data is processed in the server with state of the art DSP and only the required chunk of spectrum is sent over the network. What is sent is the actual IQ signal, not compressed audio. This means you can use all your favorite plugins to process the IF, eliminate noise and perform heavy lifting of the signals as you are used to do with locally connected SDR’s. We have a tradition of building multi-tools, so we made sure the SPY Server runs on 32/64bit Windows and Linux on Intel and ARM processors without any compromises. Low cost Raspberry Pi 3 and Odroid boards are in the party.
This software decoder appears to be an excellent choice for those people who want to perform their reception and decoding of Meteor M satellites all in Linux. Previously as explained in this previous post, you were able to receive the QPSK data in Linux with an RTL-SDR and a GNU Radio program, but then you’d still need to boot into Windows or run Wine to run LRPTofflinedecoder in order to generate the image. Now it appears that the image generation can be performed natively in Linux too with meteor_decoder. This help with creating portable automated Raspberry Pi based Meteor M decoder servers.
Meteor M is a class of Russian weather satellites that transmit live weather images of the earth as they pass over your location. They are somewhat similar to the NOAA satellites, although the Meteor satellites transmit higher quality images via a digital LRPT signal, rather than the analog APT signals used by NOAA. With an RTL-SDR, an appropriate antenna and decoding software they can easily be received.
An Example LRPT Image Received with an RTL-SDR from the Meteor M-N2 Satellite.
