Tagged: spectrum analyzer

LimeSDR CrowdFunding Closing in Four Days: 80% Funded

The LimeSDR is a new transmit capable software defined radio with a 100 kHz – 3.8 GHz frequency range, 12-bit ADC and 61.44 MHz bandwidth which is currently seeking crowdfunding. At the time of this post there is about four days left to reach the $500k goal, and it is only 80% funded. To try and reach their funding goal they have released another batch of discounted units which cost only $249 USD. After the crowd funding campaign the price will rise to $289/$299 USD. If the LimeSDR is not funded in time, they write that the project will unfortunately be put on hold and it’s future may be uncertain. We believe that this product is shaping up to be a very good TX/RX capable SDR, like the HackRF and bladeRF, but much better overall and for the same or even lower price.

Recently they also released some new updates that show off some LimeSDR features. In a post previously featured on our blog beta tester Alexandru showed how he was able to get the LimeSDR to transmit DVB-S2 HDTV. In later updates they showed how the LimeSDR can be used to:

The LimeSDR Board
The LimeSDR Board

Using the Airspy as a low cost Spectrum Analyzer with Spectrum Spy

Over on his blog VK4ZXI has been testing the Airspy with the Spectrum Spy software. The Airspy is a $199USD software defined radio that can be considered as a high end upgrade to the RTL-SDR as it has 10 MHz of bandwidth and a 12-bit ADC. The Spectrum Spy software allows the Airspy to be used as wideband spectrum analyzer. In a previous post we reviewed the Spectrum Spy software with the Airspy and found it to have an extremely fast refresh rate. Recent updates since the review have made it even faster.

In his first post VK4ZXI compares the Airspy + Spectrum Spy with the RTL-SDR running RTLSDR-Scanner and Rtl_power, two spectrum analyzer programs written for the RTL-SDR. In his tests he finds that the RTL-SDR and Airspy can obtain similar scans, but the Airspy can scan and refresh the spectrum at much faster speeds than the RTL-SDR, thanks to its 10MHz bandwidth.

Airspy + Spectrum Spy receiving the entire digital TV band over 100 MHz.
Airspy + Spectrum Spy receiving the entire digital TV band over 100 MHz.

In his second post VK4ZXI uses the Airspy + Spectrum Spy together with a cheap BG7TBL noise source to measure the response of a cavity RF filter. This is the same BG7TBL noise source that we used in our “Measuring Filter Characteristics and Antenna SWR with an RTL-SDR and Noise Source” tutorial. The results from the cavity filter measurement show that the Airspy can potentially perform on a level close to an expensive spectrum analyzer.

Measuring the response of a UHF cavity filter with Airspy + Spectrum Spy.
Measuring the response of a UHF cavity filter with Airspy + Spectrum Spy.

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.

Spektrum: New RTL-SDR Spectrum Analyzer Software

Recently a reader of RTL-SDR.com, Pavel wrote in to let us know about a new program called “Spektrum” which he has written. Spektrum runs on Windows and Linux and turns an RTL-SDR dongle into a spectrum analyzer in a similar way to rtl_power GUI front ends and RTLSDR Scanner. However one key improvement is that it is based on a version of rtl_power that has been modified by Pavel in order to make it more responsive and remove the need to wait until a full sweep is completed before you can see any results. The modified version of rtl_power can be found at https://github.com/pavels/rtl-sdr.

Spektrum also has an additional “relative mode” feature. This allows Spektrum to be easily used together with a wideband noise source to measure things like filter characteristics and the VSWR of antennas. See our previous tutorial on this here, but note that in our tutorial we used Excel instead of Spektrum to do relative measurements.

The Processing language was used to create Spektrum and Pavel has also released his processing library for accessing rtl_power functionality over at https://github.com/pavels/processing-rtlspektum-lib/releases.

Ready to use releases of Spektrum for Windows and Linux 64-Bit OSes can be downloaded from https://github.com/pavels/spektrum/releases. Note that there may be a bug with the current release which causes only a gray window to show, but we’ve contacted the author about it and it may be fixed soon.

Spektrum: A new spectrum analyzer program for the RTL-SDR
Spektrum: A new spectrum analyzer program for the RTL-SDR

New GUI for rtl_power: QSpectrumAnalyzer

A new GUI for rtl_power has been released by programmer Mikos. Although there are already several rtl_power GUIs and spectrum analyser applications that exist, Mikos developed QSpectrumAnalyzer because he found that the alternatives were either slow, closed source or Windows only.

Rtl_power is a command line tool that can be used with an RTL-SDR to create a spectrum scan of a large swath of bandwidth that is greater than the RTL-SDRs maximum sample rate.

The project can be found at https://github.com/xmikos/qspectrumanalyzer and Mikos is open to pull requests on GitHub.

QSpectrumAnalyzer GUI for  rtl_power
QSpectrumAnalyzer GUI for rtl_power

RTL-SDR As a Spectrum Analyzer

Hackaday has brought to attention a blog post by Kerry Wong which shows how the RTL-SDR can be used as a simple and inexpensive spectrum analyzer. In the past we’ve already posted numerous examples of the RTL-SDR being used as a spectrum analyzer but Kerry’s post discusses some of the do’s and don’ts that you need to think about when using a SDR as a spectrum analyzer and also provides some measurements.

During his tests he discovered that popular software like RTLSDR Scanner and SDR# either distort the spectrum or don’t display the signal amplitude correctly. Only GQRX and osmocom_fft seemed to give an accurate depiction of the spectrum.

Kerry also discusses how to calibrate the spectrum display to show proper power levels, how to set the gain for spectrum analysis and discusses some thoughts on LO leakage.

Using an RTL-SDR as a spectrum analyzer with osmocom_fft
Using an RTL-SDR as a spectrum analyzer with osmocom_fft

Raspberry Pi RTL-SDR Spectrum Analyzer Scanner

Adafruit has released a tutorial showing how to build a portable TFT screen based Raspberry Pi RTL-SDR spectrum analyzer that was inspired by the HackRF portapack. Construction of the project is very simple and the “FreqShow” python software is provided as a simple download that is ready to run once the RTL-SDR is installed on the Raspberry Pi.

The FreqShow software appears to be fully featured with the ability to change the center frequency, sample rate, and gain.  It can show on the TFT screen the real time RF spectrum of the currently tuned area or it can be switched to show a waterfall of the spectrum as well. Below is a video of the finished project that shows the software in action.

"Freq Show" Software in action on a Raspberry Pi
“Freq Show” Software in action on a Raspberry Pi with TFT Screen
Freq Show: Raspberry Pi RTL-SDR Scanner

Demo of Osmocoms ‘Phosphor’ Spectrum Visualizer

Over on YouTube, user superkuh2 has posted a video showing off osmocoms gr-fosphor GNU Radio block which shows a real time spectrum visualization using the GPU. He combines gr-fosphor with multimode for visualizing the ISM and pager bands with his RTL-SDR.

osmocom's fosphor with patchvonbraun's multimode looking at ISM + FLEX pager bands with rtlsdr