Category: Airspy

A GNU Radio DCF77 Time Signal Decoder

DCF77 is a long wave time keeping signal transmitting at 77.5 kHz from Frankfurt, Germany. It has been active since 1 January 1959. Using simple amplitude modulation, the signal encodes the current time and date, which is used by some devices like railway station clocks in Germany. Because it's a long wave signal transmitting at 50kW, it's possible to receive the signal across Europe, and sometimes even further away if propagation conditions are good.

Recently a DCF77 receiver and decoder program based on Python and GNU Radio has been uploaded to GitHub by henningM1r. It includes a simulator written in Python so you can simulate your own DCF77 signal for testing the receiver too.

Currently the decoder has been tested to work with an Airspy HF+ Discovery SDR, but it should work with any SDR capable of receiver 77.5 kHz if the GNU Radio source block is changed out.

DCF77 GNU Radio Decoder

An OpenWebRX fork with additional built in decoders

Thank you to Stefan for letting us know about a relatively modern OpenWebRX fork by luarvique that comes with additional built in decoders and features, such as SSTV, AIS, CW, RTTY, an MP3 recorder and SSTV image browser.

OpenWebRX is an open source web based SDR receiver program that allows you or others (if you allow them to), to access your SDR over the internet. It is compatible with KiwiSDR, RTL-SDR, Airspy, SDRPlay and many other software defined radio hardware. It was originally developed by Andras Retzler, but since abandoned by him, with a semi-official fork being maintained at openwebrx.de. However, other forks like luarvique can exist that implement a new set of features.

The full set of additions and improvements reads as follows:

This is the package repository for the improved version of the OpenWebRX online SDR. The new and original features available in this version of OpenWebRX:

  • Built-in SSTV decoder with background decoding.
  • Built-in AIS decoder.
  • Built-in CW decoder.
  • Built-in RTTY decoder.
  • Built-in MP3 recorder for received audio.
  • Image browser for received SSTV images.
  • Adjustable noise filtering based on spectral subtraction.
  • Adjustable tuning step.
  • Improved touch screen operation, with panning and zooming.
  • Improved scroll wheel support, with tuning and zooming.
  • Improved tuning in CW mode.
  • Bandpass filter adjustable with scroll wheel.
  • More reliable SDRPlay devices operation.
  • Better map information, with distances.
  • Better APRS map information, with weather.
  • Configurable session timeout, with a policy page.
  • HTTPS protocol support (requires SSL certificate).

The code comes packaged for Ubuntu 22.04 (amd64, arm64) and Debian 11 (amd64 arm64, armhf). There is also a ready to use Pi 4 SD card image available, linked on the GitHub readme. The original forked code can be found at https://github.com/luarvique/openwebrx.

According to discussion over on the OpenWebRX groups.io, the fork also runs on a Pi 3. In the image Neil Howard from the groups.io forum demonstrates an SSTV image he received with an SDRplay clone using the luarvique fork of OpenWebRX.

SSTV Image received by the luarvique fork of OpenWebRX. Credit: Neil Howard
SSTV Image received by the luarvique fork of OpenWebRX. Credit: Neil Howard

Stefan also notes:

The maker of OpenWebRX+ Marek and also the maker of the original version of OpenWebRX Jakob are reachable via a Telegram channel: https://t.me/openwebrx_chat

SDRangel Now Available on Android: Mobile ADS-B, AIS, APT, Digital Voice, POCSAG, APRS, RS41 Radiosonde Decoders

SDRangel is a free open source software defined radio program that is compatible with many SDRs, including RTL-SDRs. SDRAngel is set apart from other programs because of it's huge swath of built in demodulators and decoders.

Thank you to reader Jon for writing in and noting that SDRangel has recently been released for Android as a free Google Play download. This is an amazing development that could open up many doors into portable decoding setups as the Android version supports almost every decoder implemented on the desktop version. Jon writes:

It includes most of the functionality of the desktop version of SDRangel, including:

  • AM, FM, SSB, Broadcast FM and DAB, AIS, ADS-B, Digital Voice (DMR, dPMR, D-Star, FreeDV), Video (DVB-S, DVB-S2, NTSC, PAL), VOR, LoRa, M17, Packet (AX.25), Pager (POCSAG), Radiosonde (RS41), Time signal (MSF, DCF77, TDF and WWVB) modems.
  • RTL SDR, Airspy, Airspy HF, LimeSDR, HackRF and SDRplay support via USB OTG as well as networked SDRs
  • 2D and 3D signal analysis in both time and frequency domain with statistical measurements of SNR, THD, THD+N, SINAD, SFDR and channel power
  • Satellite tracker, star tracker, maps and rotator controller

It should work on Android 6 and up. It’s a straight port of the desktop application, so although it will run on a phone, probably best used on a large tablet with a stylus or mouse.

SDRangel on Android
SDRangel on Android

SDRSharp Big Guide Book Updated to V5.5

Paolo Romani (IZ1MLL) has recently released version 5.5 of his SDRSharp PDF Guide. The book is available for download on the Airspy downloads page, just scroll down to the title "SDR# Big Book" and choose your language. (At the time of this post only English and Italian are available for 5.5, but multiple languages are available for the older guides).

The latest version brings the book up to 214 pages in length, and adds information about the RTL-SDR Blog antenna kit, and new SDR# plugins like ListenInfo.

SDRSharp Big Book V5.5
SDRSharp Big Book V5.5

uSDR Updated to Version 1.6.0

Thank you to Viol for submitting news about the latest update of his uSDR software. uSDR (aka microSDR) is a lightweight general purpose multimode program for Windows that supports the RTL-SDR, Airspy, BladeRF, HackRF and LimeSDR radios. Viol highlights the latest features in the new update below: 

  • Airspy HF+ Discovery frontend support
  • ExtIO*.dll interface support. Copy ExtIO*.dll and all dependencies to the root folder and have a fun
  • ExtIO_USRP.dll and all dependencies for USRP B210 included. Just install Zadig libusb driver and go
  • LimeSDR multiple frontends switch fixed
  • FM demodulator with inverted audio spectrum
  • DCS decoder
  • additional C/C++ source examples for remote IQ passband processing TCP client
  • advanced IQ file playback options
  • display hold peak spectrum mode, zoomable and panable plot, customized colors

As always all descriptions, screenshots and binaries could be found on 

https://sourceforge.net/projects/u-sdr/

uSDR aka microSDR. A lightweight SDR receiver program for Windows.

Airspy and YouLoop Black Friday Sale Now Active: 20% OFF

Airspy is holding their annual Black Friday sale, this year offering 20% off their range of products. The sale is active at all participating resellers, which includes our own store where we have the YouLoop on sale for US$31.96 including free shipping to most countries in the world, instead of the usual US$39.95. Please note that due to EU VAT collection laws, EU customers must purchase the discounted YouLoop from our eBay or Aliexpress stores. 

The YouLoop is a low cost passive loop antenna for HF and VHF. It is based on the Möbius loop design which results in a high degree of noise cancelling. However the main drawback is that it is a non-resonant design, which means that it works best when used with ultra sensitive receivers like the Airspy HF+ Discovery. 

Some good reviews include the YouTube videos done by Frugal Radio where he reviews HF reception and VLF & LF reception with an Airspy HF+, and later tests it with an RTL-SDR Blog V3 using direct sampling. Techminds also has an excellent review on his YouTube channel. We also have a product release overview on this post from March 2020.

During the sale the price of Airspy SDRs and their upconverters are:

  • Airspy R2: $160.00 $135.20
  • Airspy Mini: $99.00 $79.20
  • Airspy HF+ Discovery: $169.00 $135.20
  • Airspy SpyVerter: $49.00 $39.20

SDRSharp Big Guide Book Updated to V5.3

Paolo Romani (IZ1MLL) has recently released version 5.3 of his SDRSharp PDF Guide. The book is available for download on the Airspy downloads page, just scroll down to the title "SDR# Big Book" and choose your language.

As before the document is a detailed guide about how to use SDRSharp (SDR#), which is the software provided by Airspy. While intended for Airspy devices, SDRSharp also supports a number of third party SDRs, including the RTL-SDR, and it is the software we recommend starting with when using an RTL-SDR.

Paolo writes:

Youssef Touil hasn't rested for a moment and the SDR# releases have been moving forward in leaps and bounds with new Denoisers (NINR), CCC, Audio/Baseband records and the new menu features.

I also had to re-update my Big Book PDF to v5.3 as a result!!

I have also implemented the SpyServer section a lot in multi OS and a chapter "Ideas and Suggestions" with two paragraphs: SDR & MacOS and the other using SDR# with two multiple monitors.

SDR# Co-Channel Canceller and Micro Tuner Updates

SDRSharp (SDR#) is one of the most popular SDR programs that is used often with Airspy and RTL-SDR devices. Recently Youssef, the developer of Airspy products and the programmer behind SDR# has again been adding new enhancements to the software that allow AM DX listeners to easily receive channels that are even on top of each other in frequency.

The Co-Channel Canceller has been in SDR# since 2020, but recently enhanced for better performance and easier use, and a 'micro-tuner' feature has been added, allowing users to easily select the overlapping channel that needs to be cancelled. 

Earlier in the year the noise canceller was also improved with a 'NINR' (Natural Intelligence Noise Reduction) algorithm that appears to be one of the best noise cancellers available in SDR software today.

Youssef's twitter @lambdaprog contains several videos demonstrating the effectiveness of the updates.