Spectrum Spy: New Spectrum Analyzer Software for the Airspy

Software defined radio's can easily be used a very wideband spectrum analyzers by quickly stepping through the spectrum at the largest stable bandwidth supported. The RTL-SDR has had this functionality for some time now through software such as rtl_power and RTL Scanner.

Now Youssef, co-creator of the Airspy and programmer of SDR# has released a similar program for the Airspy called Spectrum Spy. The software comes bundled with the latest SDR# download which can be obtained from airspy.com.

The Airspy is a $199 USD software defined radio with a similar tuning range to the RTL-SDR, but it is significantly better with its 12-bit ADC and up to 10 MHz of instantaneous bandwidth. We review the Airspy, SDRplay RSP and HackRF in this post. With its large instantaneous bandwidth and fast retuning speed the Airspy makes an excellent spectrum analyzer that refreshes very quickly.

Youssef stresses that the software is still in proof of concept stages, and various features are still to be added in the future. He writes:

A new utility app is available for download with the standard SDR# package. It allows the visualization of larger frequency spans by exploiting Airspy's fast frequency tuning capability. The scanning speed is comparable to real spectrum analyzers (may be faster even!) The project is still in a PoC state, but the basic functionality provided is fully operational.

It all started when some customer wanted an example code to implement their own SA using Airspy, so I did more than a code snippet. I hope you enjoy!

We tested the Spectrum Spy software on several bands, and recorded short videos shown below to show how fast it is. 

20 MHz Bandwidth Mobile Phone Band

50 MHz BCFM Band

100 MHz Bandwidth Mobile Phone Band

Includes the uplink and downlink portions. We used our mobile phone to make a call and you can see the uplink at 895 MHz.

1 GHz Full Spectrum

Tweeted Photos

Over on Twitter @uhf_satcom has also been testing out Spectrum Spy and has got some good shots of Ku and L-band satellite bands.

Here @supertrack_it has been using Spectrum Spy to help with the tuning of his 1420 MHz filter.

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Bootable Linux image with the telive TETRA decoder now available

Back in 2014 the telive decoder by sq5bpf was released which allowed RTL-SDR users to decode and listen in to unencrypted TETRA radio. TETRA is a type of digital voice and trunked radio communications system that stands for “Terrestrial Trunked Radio”. It is used heavily in many parts of the world, except for the USA.

If you are interested in TETRA decoding we have a tutorial available here, which has just been made much easier thanks to this image.

Installation of the telive decoder involves simply running a script, but this can be fairly difficult for someone with no Linux knowledge to do. So to make life easier sq5bpf has recently made available for download a bootable telive Linux image. By writing this Linux image to a 16GB USB drive you can boot straight into the Linux operating system and access telive. A live image like this helps avoid the hassle of having to partition your hard drive and install Linux, or try and set up a Virtual Machine that could be slow. The image is also useful to users who want to play around with GNU Radio as it is aksi preinstalled.

TETRA Decoding Windows
Telive TETRA Decoder
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RTLSDR4Everyone: Raspberry Pi guide & choosing your first dongle

Over on his blog rtlsdr4everyone author Akos has recently uploaded three new posts. The first post is about the Raspberry Pi minicomputer and the post discusses the merits of using the Raspberry Pi with an RTL-SDR dongle. The second post provides information to help people new to RTL-SDR choose their first dongle, and weighs up options between dongles that cost $10, $20, $25, $35 and $50 dollars. Finally, the third post compares two dongles on HF performance.

Raspberry Pi3 and RTL-SDR dongles.
Raspberry Pi3 and RTL-SDR dongles.
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Creating a FSK SSDV data system for High Altitude Balloons

David and Mark are building a 115 kbit/s FSK SSDV (slow scan digital video) data system for high altitude balloons. In their system, on the balloon transmit side they use a Raspberry Pi, Raspberry Pi camera and a RFM22B wireless transceiver modulator board to transmit the SSDV FSK signal. On the receive side they use an RTL-SDR dongle, low noise preamplifier and a GNU Radio program to demodulate the SSDV images. The first video below demonstrates the hardware and GNU Radio program and shows them receiving the SSDV signal. In the second video they demonstrate that the images can be received at low signal levels (-106dBm) as well, by heavily attenuating the signal.

115.2kbaud FSK Modem Test

115.387kbaud FSK Modem Test - Part 2

If you are interested, all their code for the SSDV system has been uploaded to https://github.com/projecthorus/HorusHighSpeed.

While testing the RTL-SDR for use in this system they also measured the noise figure of an R820T RTL-SDR dongle. The noise figure at maximum gain comes out at around 5.6 dB. By adding a low noise amplifier they reduce the measured noise figure down to 2 dB.

Testing the attenuated SSDV signal reception with an RTL-SDR.
Testing the attenuated SSDV signal reception with an RTL-SDR.
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Building a simple NOAA APT Antenna out of an Umbrella

In order to optimally receive NOAA weather satellite images a special satellite antenna tuned for 137 MHz should to be built. Generally either a QFH or turnstile antenna is recommended as these receive signals coming from the sky very well. If you are interested in receiving weather satellite images from NOAA satellites with an RTL-SDR dongle then we have a tutorial available here.

While QFH and turnstile antennas are not difficult or expensive to build, they still do require a small amount of electrical and construction skills. Over on YouTube user Wanderlinse shows us a possible alternative NOAA antenna that is simply made out of an old umbrella (the video is narrated in German, but it is easy to understand from the visuals). He uses a short BNC cable with crocodile clips, and connects one clip to the spines of the umbrella, and the other to the central metal shaft. For some reason this seems to create a good antenna that receives NOAA APT signals very well. To prevent wind issues he also cuts out some holes in the umbrella fabric.

Wanderlinse also shows that he can receive other signals with this umbrella antenna too, such as long wave, medium wave, shortwave, aircraft radio and ham radio.

Regenschirm Antenne NOAA APT Umbrella Antenna (quick n dirty)

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Finding GPS Signals from within the Noise Floor with an RTL-SDR

If you were to try to simply spot a GPS signal at 1.575 GHz in the spectrum on a waterfall in a program like SDR# you would probably fail to see anything. This is because GPS signals are very weak, and operate below the thermal noise floor. Only through clever processing algorithms can the actual signal be recovered.

Previously GPS and SDR enthusiast “e.p.” showed us on his blog how to use an RTL-SDR and the GNSS-SDRLIB and RTKLIB software to receive GPS and get a position lock.

Now more recently e.p. has uploaded a post that explains a bit about how GPS signals are actually detected from below the noise floor. In his post he uses GPS data collected by his RTL-SDR dongle, and a fairly simple GNU Radio program consisting of a Fast AutoCorrelation Sink block.

With real data passed through the fast autocorrelation block he is able to observe GPS signal peaks that occur every millisecond. E.p. explains the reason for this:

Why every millisecond? The coarse/acquisition code for GPS (C/A) has a period of 1023 chips which are transmitted at a rate of 1.023 MBit/s. This results in period of 1 millisecond. BAM!

In a later post e.p. has also uploaded some sample GPS data collected with his RTL-SDR so anyone can play around with GPS decoding.

Autocorrelation of a GPS signal resulting in peaks every millisecond.
Autocorrelation of a GPS signal resulting in peaks every millisecond.
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HamRadioScience Reviews the Elad FDM-DUO Software Defined Transceiver

The Elad FDM-DUO is a high end $1149 USD Italian made software defined radio transceiver (transmit and receiver) with a frequency range of 10 kHz – 54 MHz, a 16-bit ADC, a bandwidth of up to 6 MHz and can transmit with up to 5 – 8 watts. It is a product targeted at ham radio enthusiasts who want a gradual transition into software defined radios. It can work in two modes: either as a standalone computer-less radio just like a regular hardware radio, or as a fully functional computer based SDR.

The front of the FDM-DUO.
The front of the FDM-DUO.

Recently the admin of hamradioscience.com rather comprehensively reviewed the Elad FDM-DUO. His thoughts are that it is the perfect radio for those wanting to be slowly eased into the SDR world due to it’s dual mode operation. He writes:

The Italian made FDM-DUO has to be the most versatile, well designed, and well thought out SDR system currently on the market.

The review by hamradioscience goes over several points such as explaining what all the connectors on the radio are for, reviewing the ergonomics, reviewing the radio in standalone mode and in PC based SDR mode and he also reviews the companion software package. The reviewer is especially impressed with the included software, basically making the point that this system is a full SDR transceiver package (all you need in terms of hardware AND software).

Generally we recommend more general purpose and lower cost wideband VHF/UHF SDR’s like the Airspy, SDRplay RSP or HackRF (see our review on those SDRs here), but if you are not limited by budget and want to use an SDR mostly for HF amateur radio purposes then the Elad FDM-DUO looks like a winner. The author concludes with the following comment.

Elad got so many things right with the FDM-DUO that it is hard find much to criticize. Unlike so many SDR systems available today, the FDM-DUO SDR system feels like less of a “science project” and more of a finished consumer product. For those who wants a SDR radio system that “just works” and easy to use, the FDM-DUO is a great choice. Also, kudos to Elad for providing such a well done SDR program. The program was very stable over the review period. No, crashing at just the wrong time say during a contest. Heck even if it did, it wouldn’t matter much since you could just continue on using the FDM-DUO as a standalone rig. With some of the larger radio manufacturers dipping their toes in the SDR area, they should take note of what Elad has done with the FDM-DUO. Elad has truly created a very flexible multi-use system with the FDM-DUO and a darn fine SDR radio system at a very good value.

FDMDuo_SW
The Elad FDM software package.
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Dave from EEVBlog Reviews the Red Pitaya

The Red Pitaya is a type of advanced digital acquisition device (DAQ) that is marketed mainly for use as a type of digital oscilloscope. But it has an on board programmable FPGA and through various downloadable apps can be used for many different applications, such as a spectrum analyzer, impedance analyzer, bode plotter, signal generator or even as a software defined radio. 

Back in February we posted how Pavel Demin had created an SDR app for the Red Pitaya which allows it to be used with common SDR software such as SDR# and HDSDR. The Red Pitaya has an on board 14-bit ADC which when in SDR mode can receive signals from between 0 to 50 MHz with a bandwidth of up to 2.5 MHz.

Recently, Dave from the hugely popular electronics YouTube show EEVBlog reviewed the Red Pitaya. Whilst Dave doesn’t try out the SDR apps, he tests it out as an oscilloscope and also tests more of its default apps such as the spectrum analyzer.

Unfortunately in his review the Red Pitaya does not seem to live up to expectations. During operation Dave encounters problems with the WiFi connectivity, frequent problems with the web based apps crashing and freezing on him, and discovers that the provided apps are extremely rudimentary and provide very little functionality. He mentions that the device is probably more useful for people wanting to write their own customs apps for specific applications, but as an out of the box digital measurement tool it is not there yet.

The Red Pitaya
The Red Pitaya

EEVblog #858 - Red Pitaya

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