Over on the Airspy Yahoo forums and Twitter we’ve seen news of an upcoming new product from the developers of the Airspy SDR. The new product is called the Airspy HF+ and will be a low cost, yet extremely high performance HF specialty radio.
Smart AGC with real time optimization of the gain distribution
All RF inputs are matched to 50 ohms
2 x High Dynamic Range Sigma Delta ADCs @ 36 MSPS
600 kHz alias and image free output
18 bit DDC
0.5 ppm high precision, low phase noise clock
4 x Programmable GPIO’s
No drivers required! 100% Plug-and-play on Windows Vista, Seven, 8, 8.1 and 10
Industrial Operating Temperature: -45°C to 85°C
Basically, this addresses the lack of affordable and good performing receivers for HF and VHF. Target price < $200
As with all Airspy products the SDR focuses on achieving extremely high dynamic range. From the specs is seems that the dynamic range and image rejection will be high enough so that even extremely strong broadcast AM or FM stations will not require any filtering or attenuation. They are also confident enough to say that no gain sliders will need to ever be adjusted to avoid overload.
For SWLers and MW DXers this seems like the ideal SDR as it should perform as well as high end SDRs like the Perseus, RFSpace and Elad SDRs, but at a fraction of the price.
A few days ago a University research paper titled “Searching for giga-Jansky fast radio bursts from the Milky Way with a global array of low-cost radio receivers” was uploaded to the Cornell University Library. In this paper authors Dan Maoz of Tel-Aviv University and Abraham Loeb of Harvard suggest that citizen science enabled mobile phones and RTL-SDR dongles placed around the world could be used to detect fast radio bursts (FRBs) originating from within our own galaxy. The abstract reads:
If fast radio bursts (FRBs) originate from galaxies at cosmological distances, then their all-sky rate implies that the Milky Way may host an FRB on average once every 30-1500 years. If FRBs repeat for decades or centuies, a local FRB could be active now. A typical Galactic FRB would produce a millisecond radio pulse with ~1 GHz flux density of ~3E10 Jy, comparable to the radio flux levels and frequencies of cellular communication devices (cell phones, Wi-Fi, GPS). We propose to search for Galactic FRBs using a global array of low-cost radio receivers. One possibility is to use the ~1GHz communication channel in cellular phones through a Citizens-Science downloadable application. Participating phones would continuously listen for and record candidate FRBs and would periodically upload information to a central data processing website, which correlates the incoming data from all participants, to identify the signature of a real, globe-encompassing, FRB from an astronomical distance. Triangulation of the GPS-based pulse arrival times reported from different locations will provide the FRB sky position, potentially to arc-second accuracy. Pulse arrival times from phones operating at diverse frequencies, or from an on-device de-dispersion search, will yield the dispersion measure (DM) which will indicate the FRB source distance within the Galaxy. A variant of this approach would be to use the built-in ~100 MHz FM-radio receivers present in cell phones for an FRB search at lower frequencies. Alternatively, numerous “software-defined radio” (SDR) devices, costing ~$10 US each, could be plugged into USB ports of personal computers around the world (particularly in radio quiet regions) to establish the global network of receivers.
‘Fast radio bursts’ or FRBs are very brief pulses of extremely strong radio waves which have the transmit power of 500 million suns, though by the time they reach the earth they can only be picked up by radio telescopes. Radio astronomers have so far been mystified by the cause of these FRBs, and research has been hampered by the fact that the source of FRBs is notoriously difficult to pinpoint because they are unpredictable, and their energy appears to originate from all over the sky and not from a single point. Many scientists think that most FRBs must originate from outside of our galaxy, and in 2016 one was finally pinpointed as coming from a dwarf galaxy 2.5 billion light years away from earth. But the authors of the paper speculate from the rate of how often FRBs are seen, that our Milky Way galaxy could host its own local FRB event once every 30 – 1500 years.
If an FRB occurs within our own galaxy then they speculate that the received power could be strong enough to be detected by consumer level mobile phones or RTL-SDR radios, meaning that no large radio telescope dish is required for detection. By continuously monitoring for FRBs on mobile phones and/or RTL-SDRs spread around the world, a local FRB source could one day be pinpointed thanks to the high resolving power of multiple detectors spread apart.
Previously from JA7TDO who is a RTL-SDR builder in Japan we’d seen the Soft66RTL and Soft66Q which are both modified RTL-SDR units that are capable of receiving HF as well. To receive HF the Soft66RTL used an upconverter circuit and the newer Soft66Q uses an implementation of the direct sampling mod. Both units come with a preselection filter for the HF bands.
Now JA7TDO has managed to come out with a new modified RTL-SDR which he calls the Soft66IP. The Soft66IP appears to have the same specifications at the Soft66Q except without the additional preselection filter. Instead, its defining feature is that it is built together which what we assume is a Linux enabled wireless router, or some other networked single board PC. This allows you to easily get set up with rtl_tcp for streaming the radio over your network, or the internet. It seems that the unit comes preloaded with the rtl_tcp software installed, making it almost plug and play. JA7TDO advertises the features as:
RTL-SDR based
3kHz to 1.7GHz (15MHz to 24MHz is over sampling)
10/100Mbps Ethernet
DHCP
Wifi(option)
cheap price
Streaming the radio over a network might be advantageous as it allows you to place the unit near the antenna, avoiding long coax or USB cable runs. But rtl_tcp is quite bandwidth heavy, so it can have trouble streaming at higher sample rates. However, whatever single board PC is used on the Soft66IP may also be capable of running other more efficient streaming software such as OpenWebRX, or more specialized applications such as networked ADS-B decoders as well.
JA7TDO is selling the Soft66IP for a pre-order price of $80 USD which includes worldwide shipping. Shipping starts on March 1. After the pre-order phase the price may rise to $96 USD.
The Universal Radio Hacker is a software for investigating unknown wireless protocols. Features include
hardware interfaces for common Software Defined Radios
easy demodulation of signals
assigning participants to keep overview of your data
customizable decodings to crack even sophisticated
encodings like CC1101 data whitening
assign labels to reveal the logic of the protocol
fuzzing component to find security leaks
modulation support to inject the data back into the system
Inspectrum and Waveconverter are two similar programs for analyzing digital signals, however Universal Radio Hacker seems to be the most advanced.
Johannes has also uploaded four tutorial videos to YouTube which show the software in action. In the videos he uses Universal Radio Hacker to reverse engineer a wirelessly controlled power socket, and then in the last video he uses the software to transmit the reverse engineered signals via a HackRF.
This year at the end of February HAARP (High Frequency Active Auroral Research Program) scientists are planning to run several experiments that involve transmission. HAARP is a high power ionospheric research radio transmitter in Alaska, which typically transmits in the 2.7 – 10 MHz frequency region. The transmissions are powerful enough to create artificial auroras in the sky. Due to a lack of funding HAARP research was shut down in May 2013, and then later given to the University of Alaska Fairbanks (UAF) in 2015.
UAF plans to activate HAARP again at the end of Feburary, so it seems that it would be interesting to receive the waveforms with an HF capable SDR such as the RTL-SDR v3, or with an upconverter like the SpyVerter. Under some conditions the signal could propagate all over the world. It seems that the researchers are also interested in reception reports from listeners and they plan to post updates closer to the dates of transmission. The full press release reads:
The University of Alaska Fairbanks Geophysical Institute is planning its first research campaign at the High Frequency Active Auroral Research Program facility in Gakona.
The High Frequency Active Auroral Research Program facility near Gakona includes a 40-acre grid of towers to conduct research on the ionosphere. The facility was built and operated by the U.S. Air Force until August 2015, when ownership was transferred to UAF’s Geophysical Institute.
At the end of February, scientists will use the HAARP research instrument to conduct multiple experiments, including a study of atmospheric effects on satellite-to-ground communications, optical measurements of artificial airglow and over-the-horizon radar experiments.
Members of the public can follow one of the experiments in real time. Chris Fallen, assistant research professor in space physics, will be conducting National Science Foundation-funded research to create an “artificial aurora” that can be photographed with a sensitive camera. Observers throughout Alaska will have an opportunity to photograph the phenomenon, which is sometimes created over HAARP during certain types of transmissions.
Under the right conditions, people can also listen to HAARP radio transmissions from virtually anywhere in the world using an inexpensive shortwave radio. Exact frequencies of the transmission will not be known until shortly before the experiment begins, so follow @UAFGI on Twitter for an announcement.
Operation of the HAARP research facility, including the world’s most capable high-power, high-frequency transmitter for study of the ionosphere, was transferred from the U.S. Air Force to UAF in August 2015.
Anybody who wants to participate and follow HAARP experiments should follow the official and unofficial announcements linked at the top of this page. There are two main ways to participate in the campaign: by listening to the radio transmissions from HAARP itself or by photographing artificial auroras created by HAARP. Amateur (Ham) radio operators can also use temporary ionosphere irregularities created by HAARP to open new propagation modes for their own transmissions.
A shortwave radio and knowledge of the time and frequency of the HAARP transmissions provides opportunities to “listen in” since the radio wave energy often (but not always) propagates very large distances, sometimes worldwide! Shortwave radios capable of receiving frequencies in the same range that HAARP can transmit, between approximately 2.7 and 10 MHz (2700 and 10,000 kHz) allow anyone to hear HAARP transmissions provided long-distance radio propagation conditions are sufficient and the radio is tuned to one of the frequencies where HAARP is transmitting. Ham radio operators also have an opportunity to reflect (or “bounce”) their own transmissions, typically in the HF, VHF or UHF bands, off ionosphere irregularities created above HAARP during high-power experiments. This creates propagation modes that would normally only be possible during certain space weather events such as aurora.
The video below shows one of the last scheduled HAARP transmissions from when it was still under the control of the US Air Force.
Oddity Station, HAARP, multiple waveforms and frequencies, June 04, 2014
Recently we’ve heard about the ADALM-PLUTO (a.k.a PlutoSDR) which is an up and coming RX/TX capable SDR that covers 325 – 3800 MHz, has a 12-bit ADC and a 61.44 MSPS sampling rate. All this and it is currently priced at only $149 USD on Digikey (but note that it is not shipping yet). This makes it the lowest price general purpose TX capable SDR that we’ve seen so far.
Regarding the features and specs they write:
ADI’s ADALM-PLUTO is the ideal learning tool/module for radio frequency (RF), software defined radio (SDR), and wireless communications. Each ADALM-PLUTO comes with two antennas, one for frequencies of 824 HMz to 894 HMz and the other for 1710 MHz to 2.170 GHz. Each unit comes with one 15 cm SMA cable with both transmitter and receiver capabilities and is powered via USB. The self-contained RF learning module supports both half and full duplex communications and uses MATBAB and GNU Radio sink source blocks, Libiio, A C, C++, C#, and Python API.
The internal components of ADALM-PLUTO include, AD936x RF Agile Transceiver™ and Power, Micron DDR3L and QSPI Flash, Xilinx® Zqynq® programmable SoC and USB 2.0 PHY. The firmware PlutoSDR is open source and comprises technology from Das U-Boat, the Linux Kernal and Buildroot. The ADALM-PLUTO is the ideal wireless, SDR learning tool for students, hobbyists, and educators.
Features
Portable self-contained RF learning module
Cost-effective experimentation platform
RF coverage from 325 MHz to 3.8 GHz
Flexible rate, 12-bit ADC and DAC
One transmitter and one receiver (female SMA, 50 Ω)
Half or full duplex
MATLAB, Simulink support
GNU radio sink and source blocks
Libiio, a C, C++, C#, and Python API
USB 2.0 interface
Plastic enclosure
USB powered
Up to 20 MHz of instantaneous bandwidth (complex I/Q)
The PlutoSDR appears to be mainly advertised as a learning module for electrical engineering students (see the promotional PDF pamphlet here), but it there seems to be no reason why it could not be used as a general purpose SDR. In fact it seems that @csete the author of GQRX has already made his PlutoSDR work in GQRX
The PlutoSDR is also more than just an SDR. On board is a full SoC (‘System on Chip’) which includes an FPGA and ARM processor that allows Linux to run directly on the device. The processor and Linux can access the SDR and run applications on the device itself. Over on the PlutoSDR wiki there are already a few tutorials that show how to use the SDR with MATLAB, Simulink and GNU Radio.
From the specs of this SDR the main limitation seems to be the tuning range with the lowest frequency tunable being only 325 MHz. But a simple upconverter could easily solve this limitation. As it is designed to be a learning tool for University students we also expect that there will be a lot of documentation and applications eventually built for it.
At the moment the PlutoSDR does not appear to be for sale. It only seems that several early model units have been sent out to developers. But it looks like the PlutoSDR will be available on Digikey for $149 USD. We’re not sure if this is the exact pricing, as a few days earlier a lower price was shown, but even at $149 USD it seems to be a good deal.
A few days ago we received our early bird LimeSDR unit from CrowdSupply. The LimeSDR is advertised as an RX/TX capable SDR with a 100 kHz – 3.8 GHz frequency range, 12-bit ADC and up to 80 MHz of bandwidth. Back in June 2016 they surpassed their $500k goal, raising over $800k on the crowdfunding site Crowdsupply. Just recently some of the first crowdfunding backers began to receive their units in the mail. We paid $199 USD for an early bird unit, and currently a preorder unit costs $289 USD on Crowd Supply.
Unboxing
Inside the shipping box is a smaller black and green box with the LimeSDR itself inside, and a short USB pigtail with extra power header. Note that no pigtails for the u.FL antenna connectors are provided, so you will need to source these yourself, but they can be found quite cheaply on Aliexpress.
The PCB itself is intricate and heavily populated with many components. You certainly to feel like you are getting your moneys worth of engineering effort with this SDR. An enclosure is probably highly recommended if you intend to take your LimeSDR out and about, as some of the SMD components look like they could be easily knocked off with a drop.
The parcel was declared at the full value, so this may be a problem for those in countries with low customs tax thresholds.
Driver and Software Installation
For this first initial review we decided to set the LimeSDR up in Windows, with SDR-Console V3, and try to get wideband reception and some simple transmit working.
Installation was a bit rocky. Firstly one criticism is that the online documentation is all over the place, and a lot of it seems to be out of date. It was very difficult to find the current USB drivers as many links redirected to the older drivers. Finally we found drivers that work on the Lime Suite page.
Secondly there have been some apparent changes with hardware revision 1.4 which is shipping to Crowd Supply backers. This resulted in the current version of SDR-Console V3 being incompatible with the newly shipped boards, and throwing the error “Encountered an improper argument”. We had to search through the LimeSDR forums, and there we found a beta LimeSDR fix version of Console V3 released by Simon. This version worked with our board.
Once we had the LimeSDR drivers and SDR-Console V3 installed we decided to update the firmware as we’d seen on the forums that the latest firmware supposedly improved a few things. Again, performing this task was quite confusing as there was several links to outdated documentation and software all over the place. Finally we found what we think is the latest instructions, which had us download Lime Suite which comes together with the PothosSDR software. In this version of Lime Suite there is an automatic firmware update option which downloaded and flashed the new firmware easily.
It’s clear that the LimeSDR is very much a development board made mainly for experimenters, but some decent up to date documentation and a quick start guide would help new users tremendously.
Problems with HF and reception below 700 MHz
By browsing the LimeSDR forums we came across a topic where several users had claimed that the LimeSDR v1.4 (the one shipped to CrowdSupply backers) has abysmal HF sensitivity, and poor sensitivity below 700 MHz.
It seems that this lack of performance is due to the matching circuit which they have implemented. For better impedance matching at frequencies over 700 MHz they added a parallel 8.2 nH inductor. This unfortunately attenuates HF frequencies severely to the point of no reception, and also other frequencies below 700 MHz to some extent. This is a bit troubling as from the very beginning the LimeSDR has been advertised as working down to 100 kHz.
A hardware fix was found by forum user @sdr_research but this only works if you are comfortable taking a soldering iron to the board to remove that inductor. On this official blog post they also mention more fixes (EasyFix1 is the one recommended on the forums) to improve HF performance that include removing more components, and replacing some others.
The HF fix for the LimeSDR. Remove this inductor.
We performed the EasyFix1 mod, which involved removing one inductor on the PCB. Removal was very simple with a soldering iron. Even without a soldering iron it could probably be forcefully removed with some tweezers. After removing that inductor we saw HF spring back into life, with reception working all the way down to the MW broadcast AM band.
LF reception still seems to be a bit weak. We were able to receive an NDB down to about 300 kHz, but very weakly in comparison to other SDRs.
The image below shows the difference in HF reception before and after the mod.
Before and after the mod. Bottom waterfall shows signal levels before the inductor mod, top waterfall shows signal levels after removing the inductor.
Fortunately it seems that LimeSDR is trying to make this right, and just today they issued an update that confirms the issue and offers a fix. They are offering an option for unshipped boards to be modified to improve HF performance before they ship out, and a replacement option for those who have already received boards. The deadline for applying for a modification is February 21, 2017.
DB Gain’s review first covers the features of the RSP2, and some basic SDR vs Analogue theory. He talks a bit about what criteria makes a good SDR and discusses why SDRs are so good for digital work. The review then goes on to talk about the SDRuno software, sensitivity settings, and voice mode work. The review mostly concerns the RSP2’s use on HF, and in this respect DB Gain appears appears to be extremely impressed with the results that the RSP2 gives him.
