Several new Airspy HF+ Reviews

The new Airspy HF+ SDR receiver has now been shipped to multiple customers and reviewers, and new reviews are coming online fast. If you weren't already aware, the Airspy HF+ was a hotly anticipated low cost, but high performance HF speciality SDR receiver. The claims are that it can compete with the high end $500 US+ units. We have our own review of an early model here. Below are some new reviews that we are aware of.

Nils DK8OK's photo of the Airspy HF+.
Nils DK8OK's photo of the Airspy HF+.

Nils Schiffhauer - DK8OK

On his blog Nils presents us with a comprehensive set of audio recordings comparing the $525 US Elad FDM-S2 with the $199 US Airspy HF+. He compares the two receivers on various shortwave broadcast stations, time stations, and an airport VOLMET. The recordings are identical, with the two radios recording the same signals simultaneously via a splitter.

Both receivers produce excellent results so you will probably need headphones and keen ears to be able to tell the difference.

Mile Kokotov

In this review YouTube video Mile Kokotov presents a comparison of the Airspy HF+ vs. the ColibriNANO, a similarly specced SDR dongle. He writes:

In this video I am comparing two high quality SDR Receivers: Airspy HF+ and ColibriNANO. They both have 16 bit Analog-to-Digital Converter. Comparison was made with the same overall conditions.

For example, both receivers was set with equal size spectrum windows, with the same amount of decibels in their scale, and the same high of the spectrum windows.
ColibriNANO has LNA gain slider which was set to maximum SNR.

Airspy HF+, on the other hand, has no LNA gain control.
The SV2HQL/Beacon was chosen as a test signal on 3579.32 kHz (on 80m band)

Antenna is half-wave resonant Dipole (40 meters long) for 80m band.

In the second part of the video I was inserted 27 dB external Attenuator on both receivers. ColibriNANO automatically increased the LNA gain and sets itself to maximum SNR. With this amount of attenuation, The Airspy HF+ noise floor level was at about the same place in spectrum window like ColibriNANO, Unlike in the first part of the video, when no external attenuator was used.

Both SDR-receivers are very good! Which is better? I leave on you to judge...

Airspy HF+ vs ColibriNANO Comparison on 3.579 MHz

Mile also does a second test with his HF+ and an active Mini-Whip antenna. He writes:

Airspy HF+ is superb High-Dynamic HF and VHF SDR-receiver and I am impressed with it. In order to minimize possible negative effect on signal path from antenna connector to tuner input, Airspy HF+ has no internal attenuator. Developers takes in account that this SDR-receiver has enough dynamic range that is very difficult to overload it. Actually it is true for most cases. But, if we want to use some type of active antenna (with internal amplification) like Mini-Whip Active Antenna for example, it is good idea to add an external attenuator between antenna and receiver HF-input connector, in order to have opportunity to lower the signal level from the active antenna, and to avoid possible overload issues. In this video I am presented some scenario (receiving MW AM band) when my homemade external step-attenuator is more than welcome! By the way, the external step-attenuator is very easy to made in almost no money. All you need is 9 resistors, three switches and one metal box) I have 5.5 dB switch, 10.5 dB switch and 22 dB switch. It can be set for 8 various combinations: 0, -5.5 dB, -10.5 dB, -16 dB, -22 dB, -27.5 dB, -32.5 dB and -38 dB.

You can see on this video that the AM Broadcast signal from Macedonian Radio on 810 kHz is very strong. The Antenna is about 30 km from my house. It is self standing huge 185 meters high vertical antenna, radiating enormous RF-power, so I have to use my homemade attenuator I mentioned it before.

Airspy HF+ SDR Receiver with Mini-Whip Active Antenna and External Attenuator

The SWLing Post Blog

Here Thomas of the SWLing post blog has posted a brief review of his HF+ unit. He notes how the HF+ is very compact, with a durable enclosure and how easy it was to set up with it being completely plug and play. So far Thomas hasn't fully evaluated the performance, but his first impressions are good.

Adam 9A4QV

In his two videos Adam doesn't directly review the Airspy HF+, but he does show some pretty impressive reception with his Skyloop antenna.

CQWW-2017 the end of the contest AirspyHF+

CQWW-2017 using AirSPY HF+ and 250 feet long skyloop antenna

RadioHobbyist (Update: 8 Dec 2017)

This review by RadioHobbyist just came online shortly after this post went out. It compares the HF+ against the expensive $1449 US NetSDR using sound samples from both radios. The difference between the two radios is almost undetectable.

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GR-Con17 Talks: GPS Beamforming with RTL-SDRs, Direction Finding with RTL-SDRs on Android and much more

GRCon17 is the yearly convention all about GNU Radio and the talks are generally all about technical cutting edge developments in the software area of the SDR world. If you didn't already know, GNU Radio is an open source tool that makes implementing digital signal processing code significantly easier by providing a framework and several ready to use DSP blocks. It is an advanced tool used a lot in industry and research, but the visual nature of the blocks means that the basics can be easily learned in a few days. See Micheal Ossmans video tutorials for an excellent introduction.

This year at GRCon17 there were multiple interesting talks, and over the last few days videos of them have been released on YouTube. Slides for each presentation are also available in the YouTube description boxes. The full list of presentations can also be found on the Technical Processing page at GNURadio. A selection of our favorites videos are presented below, with several talks utilizing low cost RTL-SDRs as the core radio in the research.

GPS Beamforming with Low-Cost RTL-SDRs - Wil Myrick

In this talk Wil Myrick discusses how he's been using low cost RTL-SDR dongles to perform beamforming experiments with GPS signals.

GRCon17 - GPS Beamforming with Low-Cost RTL-SDRs - Wil Myrick

Real-Time Direction Finding Using Two Antennas on an Android Phone - Sam Whiting

In this talk Sam Whiting shows how he used two coherent RTL-SDR dongles running on on an Android phone for direction finding. At the end of the video he demonstrates his results.

GRCon17 - Real-Time Direction Finding Using Two Antennas on an Android Phone - Sam Whiting

Hacking the Wireless World 4.0 - Balint Seeber

In this video Balint Seeber continues with his popular Hacking the Wireless World series of talks and this time talks about FMCW & Passive Radar and FPV decoding with SDRs.

GRCon17 - Hacking the Wireless World 4.0 - Balint Seeber

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Akos Tests the RTL-SDR Blog Multipurpose Dipole Kit

Over on his blog 'Radio For Everyone' Akos has been testing out our multipurpose dipole kit for ADS-B reception. He goes over each of the components in the kit and does some tests with the kit set up outside. His results show that the dipole kit when used with the smaller antennas can compete favorably with the more expensive FlightAware antenna. We note that the dipole antenna is not designed to be used outdoors for extended periods of time as Akos did as they are not weather proofed for rain. The antennas are designed to be used temporarily outside in good weather conditions. Waterproofing could potentially be achieved by oiling the metal, or potting with hot glue etc.

Akos also does a comparison of the dipole used in two configurations. In one configuration the antenna is used in the recommended vertical orientation, and in the other position in a bunny ears configuration. Antenna theory says that the vertical orientation will work best as ADS-B signals are vertically polarized, and the results confirm that that is true.

FlightAware Antenna vs Dipole
Akos' Results: FlightAware Antenna vs Dipole
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The Open Source OVI-40 SDR Transceiver

Thanks to various contributors for letting us know about the OVI-40, a new open source DIY SDR ham radio transceiver project that is now available for ordering. The OVI-40 appears to be a German project that is based on the mcHF transceiver. It is a standalone SDR transceiver (no PC required) with a frequency range of DC - 75 MHz. Most discussion appears to be happening in German on their forums, so it is a little difficult to get English information about it.

The kit has recently been released for preorder. The transceiver is a kit involving SMD soldering, but can be ordered fully soldered for 202 Euros (~$240 US) + taxes. The LCD screen is an additional 24 - 27 Euros. The kit without soldering done costs 112 Euros (~$132 US) + taxes.

The advertised details and specs are listed below:

OVI40-SDR is a transceiver which covers VLF...75MHz. It is mainly a DIY project - but all PCBs will also be available as soldered, aligned / programmed PCBs for all those, who do not have the skill to build a complex SMD project by themself or do not want it. OVI40-SDR will also be available as "only RX" and can be expanded with TX stages later.

Developer team takes inspirations from all existing commercial and DIY projects to get a SDR which combines possibly the best of all of them. But OVI40-SDR is not only a TRX - it is a philosophy. A community based working together, regardless of different countries, languages, religions, political systems - all are working together to get a very nice transceiver for themselfes and for others who are coming to the project later - wants to show, what people can reach if they are working together and do not struggle against each other. HAM radio always has connected the world - using the possibilities of the internet adds much more power for community working.

  • RX from VLF (~ a few KHz) ... 4m, possibly 2m Including
  • TX 160m ... 4m: 50W, 2200m, 630m and 4m (2m if Implemented): 10 ... 20mW SMA Out
  • continuosly tuned preselection
  • PA works using double LDMOSFET, independent BIAS adjusted. BIAS is internally Measured via A / D and can be set in menu Directly in [mA].
  • TX and RX mixer with very low capacity to minimize LO leakage
  • true RX QSD mixer using instrumental amplifiers
  • all internal Voltages (8V, 5V) are generated using well-shielded switching regulators. Additionally switching frequency is shifted via firmware so that never harmonics are present in the RX spectrum
  • included hardware for measuring antenna (sweep) using logarithmic amplifier
  • output of an independent selectable rf to SMA plug. I am experimenting to use this as a beacon WSPR Which can run parallel to radio
  • usage as possible network analyzer
The OVI-40 Kit Assembled
The OVI-40 Kit Assembled
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RFSim99 for Modern Windows Versions: Free RF Simulation Tool

RFSim99 is an old but still very useful piece of free software for designing and simulating RF circuits such as filters, attenuators, matching circuits, RF components with S-parameters and so on. It is not a high end tool, but is more than good enough for hobbyist and ham level designs.

One issue up until recently with RFSim99 was that it was so old that it would only run on Windows XP computers. To run on a modern PC you needed to use a virtual machine, or the Windows built in XP emulation, which was only available on Professional/Ultimate Windows versions and has since been discontinued in Windows 10.

However, we have just found AD5GG's blog where earlier in the year he posted a standalone version that actually works in modern Windows versions (7, 8, 10) without the need for any virtual machines.

RFSim99 is fairly simple to learn. Just place down two measurement ports (in/out) and lay down your RF components on the grid. Then connect them up with a wire and place grounds. Click on the simulate button to see a graph of the response and return loss. There are even built in calculators in the Tools menu which can automatically design and simulate filters for you.

Designing a simple filter in RFSim99
Designing a simple filter in RFSim99
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XTRX SDR Campaign Now Live: Mini PCIE Based TX/RX SDR for $199

Back in early November we posted about the upcoming XTRX SDR, which is a small form factor 2 x 2 MIMO TX and RX capable SDR that is designed to fit into laptop Mini PCIE card slots. It is based on the LimeSDR RF chips, and has a tuning range of 10 MHz - 3.7 GHz, with a sample rate of up to 120 MSPS. It is also has some interesting additional features such as a built in GPSDO and an onboard FPGA which can be used to accelerate DSP tasks as well. The Mini PCIE interface was chosen for it's low latency transfer rates.

The card is designed for use cases such as creating LTE cellular networks, creating software defined 2G/3G/4G modems and using on board drones and in embedded systems. It can also be used for standard wideband monitoring and of course any other SDR applications compatible with Lime chips.

Today the crowdfunding campaign for the XTRX has begun. The early bird pricing is $179 USD (with 71 left at the time of this post - going down fast!), and the regular price is $199 USD. There are accessories available as well such as antenna and cable kits, a PCIe x2 adapter and a USB 3.0 adapter kit with enclosure. The XTRX team are hoping to raise 90k USD, with already 8k USD having been raised at the time of this post.

The XTRX Board
The XTRX Board
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Exploring Vulnerabilities in Tire Pressure Monitoring Systems (TPMS) with a HackRF

Over on YouTube the channel "Lead Cyber Solutions" has uploaded a video presentation for the Cyber Skills Competition. In the video Christopher Flatley, James Pak and Thomas Vaccaro discuss a man-in-the-middle attack that can be performed on vehicle Tire Pressure Monitoring Systems (TPMS) with a transmit capable SDR such as a HackRF.

A TPMS system consists of small battery powered wireless sensors placed on a vehicles wheels which automatically monitor tire pressure. An LCD basestation usually exists on the dashboard of the car indicating live tire pressure. Most modern cars come with this feature, and it is simple to retrofit an older car with an aftermarket TPMS system.

The idea behind the vulnerability is that a HackRF can be used to reverse engineer the TMPS signal, and then re-transmit a new fake signal that causes the base station to read the tire pressure as low. This can set off an alarm in the car and possibly cause someone to pull over. More alarmingly, they discuss how tractors have automatic tire inflation systems which work using similar sensors. A false low pressure reading could cause the tractor tires to over inflate and be damaged.

Vulnerabilities in Vehicle TPMS (Exploit & Hacking)

In the past we have also posted about Jared Boon's work on TPMS where he shows how privacy could be breached by monitoring and tracking TPMS identifiers.

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Testing out SDRAngel with an RTL-SDR

SDRAngel is a general purpose SDR program similar to other programs like SDR#, HDSDR and SDR-Console. It is compatible with Windows and Linux systems. However, SDRAngel has certain features that make it a good program to have in your SDR software arsenal.

One good feature is that if you have a TX capable SDR like a HackRF, PlutoSDR, BladeRF or LimeSDR then SDRAngel can also be used for TXing. Marty Wittrock has done a lot of previous work figuring out how to TX with LimeSDR and SDRAngel.

If you're only interested in RXing then SDRAngel also has some convenient features such as a built in DSD decoder which can be used to easily decode DMR/MOTOTRBO, dPMR, D-STAR and Yaesu System Fusion (YSF). The decoder is based on the DSDcc library which is a complete rewrite of the original open source DSD software.  It is not quite as developed and feature rich as DSD+, but still does the job decently. SDRAngel also has LoRa and analogue TV (ATV) decoders built in as well, although the ATV decoder kept crashing the software for us.

SDRAngel also supports multiple VFO's on the same bandwidth, has built in decimation, a nice phosphor effect RF spectrum display and a frequency manager. There is also the ability to run multiple SDRs in the same software instance at the same time.

We gave SDRAngel a try on Windows and were able to easily get it up and running with an RTL-SDR. Regular WFM, FM, AM, SSB etc modes all work fine and so does the DSD decoder which we tested on a DMR signal. Getting it to decode was extremely simple, just add a DSD Demodulator channel, then click on the signal and you should be instantly decoding. It is probably the easiest way to get started on decoding a non-trunking digital voice channel, but for trunking channels and P25 signals you should probably still use Unitrunker and DSD+ or SDRTrunk.

SDRAngel Screenshot
SDRAngel Screenshot

Below is a brief tutorial on getting up an running with SDRAngel on Windows with an RTL-SDR:

  1. Download the latest version of SDRAngel from the releases section of the GitHub. Only a build for Windows x64 is available and this has the filename sdrangel64_v3.8.4.7z (version number may change in the future). Linux .deb files are also available for various Ubuntu versions.
     
  2. Using 7zip, extract the 7z file to a folder on your PC.
     
  3. Plug in your RTL-SDR dongle, and run sdrangel.exe. We assume zadig has already been previously run to install the RTL-SDR drivers.
     
  4. On the left under 'sampling devices control' click on the small hand icon. A drop down box will pop up, and from here you should be able to select the RTL-SDR. Press ok.
     
  5. Now you can click the green play button on the top left to start the SDR.
     
  6. By default the display bandwidth is zoomed in very closely with x16 decimation and a sample rate of 1 MSPS. So in the top left box change "Dec" to 1, and increase the sample rate to 2 or 2.4 MSPS if you like.
     
  7. We suggest also clicking on the 'DC' button in the top left to remove the DC spike.
     
  8. Now you can tune around just like in other software by using the frequency numbers in the top left.
  9. If you want a spectrum analyzer display, go to the bottom left box, and click on the blue spectrum icon.
     
  10. Unlike most other software you need to add a demodulator first before you can click on a signal and listen to it. The list of available demodulators can be found in the second box on the left, just below the hand icon which you used to add the RTL-SDR.
     
  11. Select the correct demodulator for your signal of interest (e.g. WFM, NFM, AM, DSD, LoRa etc...), and then click the "+" icon. This will add the demodulator to the right of the SDRAngel window. You may want to drag the right window a little large if you cannot see all of the demodulator option as well.
     
  12. Now you can click on the signal in the spectrum window to move the VFO and begin demodulating the signal. You can explore the demodulator options on the right.
     
  13. Multiple demodulators can be added if desired, just repeat steps 8 - 10. If you add more than one demodulator, the VFO's will need to be dragged.
     
  14. If you're having trouble getting a digital voice signal with DSD to be recognized, try zooming in with the decimation feature or reducing the sample rate. It doesn't seem to work too well with higher bandwidths.
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