Tagged: rtl-sdr

Antennas for Receiving Shortwave Indoors with an SDR

Over on the swling.com blog admin Thomas has been exploring various indoor antenna options for pairing with an HF capable software defined radio. He notes that unless you happen to live in isolation, you're highly likely to experience RFI problems with standard wire antennas. Instead he recommends looking into magnetic loop antennas which are significantly more resistant to urban electric field based RFI noise, and they can also be rotated to null out any other local noise sources. Thomas then goes on to highlight some of the best commercial magnetic loop options for sale. There is also some good advice in the comments section.

We note that magnetic loop antenna seem to work fairly well with the RTL-SDR in V3 in direct sampling mode, but you may need to filter out the broadcast AM band to avoid overload if the loop doesn't do this already.

An example small PK-Loop antenna for receiving shortwave with an SDR.
An example small PK-Loop antenna for receiving shortwave with an SDR.

RTLSDR-Airband V3 Released

Thanks to RTL-SDR.com reader Lee Donaghy for writing in and little us know that RTLSDR-Airband was recently updated to include SoapySDR support. This allows the software to now work with almost any SDR including the RTL-SDR, Airspy, SDRplay, HackRF, LimeSDR and more. They have also removed the 8-channels per device limitation and applied various bug fixes too. The full changelog is posted at the end of this post.

RTLSDR-Airband is a Linux based command line tool that allows you to simultaneously monitor multiple AM or FM channels per SDR within the same chunk of bandwidth. It is great for monitoring narrowband communications such as aircraft control and can be used to feed websites like liveatc.net, or for use with a Icecast server, or simply for continuously recording multiple channels to an MP3 file locally. It is also very useful for those running on low powered computing hardware who want software that uses less CPU power than a full GUI program like GQRX or CubicSDR.

Version 3.0.0 (Feb 10, 2018):

  • Major overhaul of the SDR input code - now it's modular and hardware-agnostic (no longer tightly coupled with librtlsdr).
  • Support for SoapySDR vendor-neutral SDR library - any SDR which has a plugin for SoapySDR shall now work in RTLSDR-Airband.
  • Support for Mirics DVB-T dongles via libmirisdr-4 library.
  • Support for RTLSDR is now optional and can be disabled at compilation stage.
  • Removed the 8-channels-per-device limit in multichannel mode.
  • Configurable per-device sampling rate.
  • Configurable FFT size.
  • Support for multibyte input samples.
  • Support for rawfile outputs (ie. writing raw I/Q data from a narrowband channel to a file for processing with other programs, line GNUradio or csdr).
  • INCOMPATIBLE CHANGE: removed rtlsdr_buffers global configuration option; buffer count can now be adjusted with a per-device "buffers" option.
  • INCOMPATIBLE CHANGE: removed syslog global configuration option; syslog logging is now enabled by default, both in foreground and background mode. To force logging to standard error, use -e command line option.
  • Added -F command line option for better cooperation with systemd. Runs the program in foreground, but without textual waterfalls. Together with -e it allows running rtl_airband as a service of type "simple" under systemd. Example rtl_airband.service file has been adjusted to reflect this change.
  • Added type device configuration option. It sets the device type (ie. the input driver which shall be used to talk to the device). "rtlsdr" is assumed as a default type for backward compatibility. If RTLSDR support has been disabled at compilation stage, then there is no default type - it must be set manually, or the program will throw an error on startup.
  • Frequencies in the config can now be expressed in Hz, kHz, MHz or GHz for improved readability.
  • Lots of bugfixes.
  • Rewritten documentation on Github Wiki.

An Intuitive Tutorial on SDR, The Frequency Domain and IQ Data

Over on his website P. Lutus has written up a useful article that introduces us to some common SDR hardware (RTL-SDRs, upconverters and the HackRF), mentions some common SDR software, and then dives into some SDR theory explaining concepts like the frequency domain and IQ sampling.

The theory sections in particular are explained quite intuitively with animated and interactive graphs that really help with visualizing the math. The explanations are short and not math heavy, so if you have half an hour you can learn some of the basic theory behind making SDRs work.

IQ Visualized on an interactive graph.
IQ Visualized on an interactive graph on P.Lutus' blog post.

SDR# Dark Mode Plugin

A few days ago Eddie MacDonald released his Tuner Knob plugin for SDR#. Today he's released a new plugin called "SDR# Dark Mode" over on our forums. This plugin is very simple in that is just makes the SDR# interface black, which should be better on the eyes those using the app at night. The plugin also adds two other options which allow you move the tuning toolbar to the bottom of the screen and remove all padding to save some screen space. The three options in the plugin are:

"Night Mode" or "Regular Mode" - allowing the app to be black or not
"Bottom Tool Bar" - allows you to place the radio control tool bar on the top or bottom of the app
"Remove Padding" - remove the 10px border around all the controls giving you a tiny amount of more workable space.

The plugin can be downloaded from the file uploaded on the third post on the announcement thread.

Normal Mode

Normal Mode

Dark Mode + Remove Padding

Dark Mode + Remove Padding

Dark Mode + Remove Padding + Toolbar on Bottom

Dark Mode + Remove Padding + Toolbar on Bottom

Antennas for Receiving Shortwave Indoors with an SDR

Over on the swling.com blog admin Thomas has been exploring various indoor antenna options for pairing with an HF capable software defined radio. He notes that unless you happen to live in isolation, you're highly likely to experience RFI problems with standard wire antennas. Instead he recommends looking into magnetic loop antennas which are significantly more resistant to urban electric field based RFI noise, and they can also be rotated to null out any other local noise sources. Thomas then goes on to highlight some of the best commercial magnetic loop options for sale. There is also some good advice in the comments section.

We note that magnetic loop antenna seem to work fairly well with the RTL-SDR in V3 in direct sampling mode, but you may need to filter out the broadcast AM band to avoid overload if the loop doesn't do this already.

An example small PK-Loop antenna for receiving shortwave with an SDR.
An example small PK-Loop antenna for receiving shortwave with an SDR.

RTLSDR-Airband V3 Released

Thanks to RTL-SDR.com reader Lee Donaghy for writing in and little us know that RTLSDR-Airband was recently updated to include SoapySDR support. This allows the software to now work with almost any SDR including the RTL-SDR, Airspy, SDRplay, HackRF, LimeSDR and more. They have also removed the 8-channels per device limitation and applied various bug fixes too. The full changelog is posted at the end of this post.

RTLSDR-Airband is a Linux based command line tool that allows you to simultaneously monitor multiple AM or FM channels per SDR within the same chunk of bandwidth. It is great for monitoring narrowband communications such as aircraft control and can be used to feed websites like liveatc.net, or for use with a Icecast server, or simply for continuously recording multiple channels to an MP3 file locally. It is also very useful for those running on low powered computing hardware who want software that uses less CPU power than a full GUI program like GQRX or CubicSDR.

Version 3.0.0 (Feb 10, 2018):

  • Major overhaul of the SDR input code - now it's modular and hardware-agnostic (no longer tightly coupled with librtlsdr).
  • Support for SoapySDR vendor-neutral SDR library - any SDR which has a plugin for SoapySDR shall now work in RTLSDR-Airband.
  • Support for Mirics DVB-T dongles via libmirisdr-4 library.
  • Support for RTLSDR is now optional and can be disabled at compilation stage.
  • Removed the 8-channels-per-device limit in multichannel mode.
  • Configurable per-device sampling rate.
  • Configurable FFT size.
  • Support for multibyte input samples.
  • Support for rawfile outputs (ie. writing raw I/Q data from a narrowband channel to a file for processing with other programs, line GNUradio or csdr).
  • INCOMPATIBLE CHANGE: removed rtlsdr_buffers global configuration option; buffer count can now be adjusted with a per-device "buffers" option.
  • INCOMPATIBLE CHANGE: removed syslog global configuration option; syslog logging is now enabled by default, both in foreground and background mode. To force logging to standard error, use -e command line option.
  • Added -F command line option for better cooperation with systemd. Runs the program in foreground, but without textual waterfalls. Together with -e it allows running rtl_airband as a service of type "simple" under systemd. Example rtl_airband.service file has been adjusted to reflect this change.
  • Added type device configuration option. It sets the device type (ie. the input driver which shall be used to talk to the device). "rtlsdr" is assumed as a default type for backward compatibility. If RTLSDR support has been disabled at compilation stage, then there is no default type - it must be set manually, or the program will throw an error on startup.
  • Frequencies in the config can now be expressed in Hz, kHz, MHz or GHz for improved readability.
  • Lots of bugfixes.
  • Rewritten documentation on Github Wiki.

An Intuitive Tutorial on SDR, The Frequency Domain and IQ Data

Over on his website P. Lutus has written up a useful article that introduces us to some common SDR hardware (RTL-SDRs, upconverters and the HackRF), mentions some common SDR software, and then dives into some SDR theory explaining concepts like the frequency domain and IQ sampling.

The theory sections in particular are explained quite intuitively with animated and interactive graphs that really help with visualizing the math. The explanations are short and not math heavy, so if you have half an hour you can learn some of the basic theory behind making SDRs work.

IQ Visualized on an interactive graph.
IQ Visualized on an interactive graph on P.Lutus' blog post.

SDR# Dark Mode Plugin

A few days ago Eddie MacDonald released his Tuner Knob plugin for SDR#. Today he's released a new plugin called "SDR# Dark Mode" over on our forums. This plugin is very simple in that is just makes the SDR# interface black, which should be better on the eyes those using the app at night. The plugin also adds two other options which allow you move the tuning toolbar to the bottom of the screen and remove all padding to save some screen space. The three options in the plugin are:

"Night Mode" or "Regular Mode" - allowing the app to be black or not
"Bottom Tool Bar" - allows you to place the radio control tool bar on the top or bottom of the app
"Remove Padding" - remove the 10px border around all the controls giving you a tiny amount of more workable space.

The plugin can be downloaded from the file uploaded on the third post on the announcement thread.

Normal Mode

Normal Mode

Dark Mode + Remove Padding

Dark Mode + Remove Padding

Dark Mode + Remove Padding + Toolbar on Bottom

Dark Mode + Remove Padding + Toolbar on Bottom

Video Tutorial: Setting up DMR Decoding with SDR#, DSD+ and an RTL-SDR

Over on YouTube user Tech Minds has uploaded a useful video which shows how to set up DMR decoding with SDR#, VB-Cable, DSD+ and an RTL-SDR dongle. He also uses the DSD plugin for SDR# which makes controlling the command line DSD+ software a little easier. If you are interested we also have a short tutorial on DMR/P25 decoding available here. The video starts from downloading and installing the software, and explains every step very carefully, so it is a very good starting video for beginners.

DMR (aka MotoTRBO or TRBO) is a digital voice protocol used by Motorola radios. Software like DSD+ is required to listen to it, but it can only listen in if the signal is unencrypted.

Tech Minds has also uploaded several other tutorial videos to his channel over the last few months including guides on how to set up the ham-it-up upconverter, ADS-B tracking, using a Raspberry Pi to create a FM transmitter and more.

Visual Tuner Knob Plugin for SDR#

Thank you to Eddie MacDonald for submitting his new SDR# plugin to us via our forums. Eddie's plugin is called the 'Tuner Knob Plugin', and simply enables a visual tuner knob on the screen for adjusting the frequency. This plugin could be useful especially for those running SDR# on touchscreen tablets or laptops. To install the plugin copy the .dll file to the SDR# directory and copy and paste the magicline.txt into the plugins.xml file. We tested the plugin on our PC and found it to run well.

We have uploaded the plugin here for all to download.

Eddie writes about the plugin:

Programming the plugins is not so easy considering their is very little documentation and few examples on the net. There may be a few bugs I have not caught (but i hope i have caught them all.)

This DLL was compiled and tested on a Windows 7 x64 machine and the DLL is compiled for both x86 and x64 platforms. I have tested it on SDR# Version v1.0.0.1635

I am not certain which previous versions it may or may not run on. However, being built on the 4.6 .Net framework it should work with Win7 on.

I built this plugin because i got tired of holding down buttons and waiting for the frequency changes. I figured this was a simpler method (even though some people hate rotary style controls on windows) It works exceptionally well with a touch screen.

As previously mentioned in the forum post I created the 'remote' to test my programming for future plugins for DSP

While some may not find a use for the remote I made it this way for my wife who like to cruise the dial and just see what she can pick up.

Tuner Knob Plugin for SDR#
Tuner Knob Plugin for SDR#

Running a NAS, Torrentbox and ADS-B RTL-SDR Server all on the same Raspberry Pi 3

Most readers are familiar with the Raspberry Pi 3 and how it can be used with RTL-SDR applications such as ADS-B reception. However, one does not need to dedicate an entire Pi 3 to a single task as they are more than powerful enough to run multiple applications at once.

Over on his blog 'Radio for Everyone' Akos has uploaded a tutorial that shows how he set his Raspberry Pi 3 up as a simultaneous Network Attached Storage (NAS), Torrentbox  and ADS-B server. A NAS is simply a hard drive or other data storage device that can be accessed easily over a network instead of having to be connected directly to a PC. A torrentbox is a device such as a Raspberry Pi 3 running torrent software so that you can download torrent files 24/7 without needing a PC on all the time.

Akos' tutorial shows how to set everything up from scratch, starting from writing the Raspbian SD Card and connecting to it via SSH. He then goes on to show how to install the torrent software, set up the NAS and finally set up ADS-B reception.

Pi 3 as a NAS, torrentbox and ADS-B server.
Pi 3 as a NAS, torrentbox and ADS-B server.

Understanding the Fourier Transform: Video Tutorial from 3Blue1Brown

The Fourier Transform is a fundamental concept when it comes to digital signal processing (DSP) and thus understanding how software defined radios like the RTL-SDR work. It is the key bit of maths behind the RF/waterfall spectrum displays and frequency selection features used on your SDR software. In basic terms all the Fourier Transform does is take a signal (for example an RF signal from an antenna, or a sound sample), and break it down into its component frequencies. This allows us to see each individual frequency spike in the RF/waterfall spectrum display in programs like SDR# from the mash of signals that arrive at the antenna. But understanding how the Fourier Transform does this can be a little tricky to understand.

3Blue1Brown is a very successful YouTuber whose channel is all about explaining complex mathematical concepts in an animated and easy to digest format. His latest video explains the Fourier Transform, and is a great starting point for those trying to learn DSP concepts. He focuses on audio frequencies as that is the most intuitive, but the exact same concepts can be applied to radio frequencies.