Kategori
Radio

Flamingo+ FM

This article is written after I received my giveaway prize of LaNA, Flamingo+ FM, and HF Balun 1:9 from the amazing Nooelec!

Nooelec is a company that sells Software Defined Radio stuffs, their SMArt SDR seems to be the premium in RTL-SDR class. What I’m trying to review first is the Flamingo+ FM, since it’s the simplest out of them.

Notch Filter

Basically, the Flamingo is a FM notch filter, it does as expected, blocking out FM broadcast signal. FM broadcast in my hometown is quite full, occupying the whole frequency band plan for FM broadcast from 87MHz to 108MHz. This band has a center frequency of 97.5MHz, which is exactly where the Flamingo+ is designed for.

Figure 1. Flamingo+ FM, 7 order notch filter for FM broadcast

As the brochure said, Flamingo+ FM is a 7 order notch filter that is centered on 97MHz. This can easily be realized by passive LC filters, with 7 pairs of inductors and capacitors connected in series or parallel. There is two ways to implement this filter, using the Pi configuration or T-configuration. You can find more information on WA4DSY on how the band-stop filter is configured. LC notch filter is a passive device so it does not require any Bias-Tee to operate. Calculating the components for every inductor and capacitor for the filter is done by following the Chebyshev/Butterworth/Bessel polynomial functions.

notch-filter
Figure 2. 5th order notch T-filter

Using the Notch Filter

Using the Notch filter is simple, there is an input port and output port, technically, both of them can be used interchangeably, but the Flamingo+ FM design adds an ESD diode in the input to prevent voltage transients from the antenna. The antenna is connected to the Input port of Flamingo+ FM filter, then the output port is connected to the SDR directly via a SMA barrel. Getting the ports mixed up should be okay, but you will be losing the ESD protection on the antenna if you got them mixed up.

When to use this FM notch filter? This is dependent on the location of the SDR-based solution that we’re trying to deploy. This FM notch filter may be needed if there is a high powered FM-broadcast in close proximity with the SDR site.

If I had a NanoVNA, I would probably measure the S11 and S21 performance of the filter, since I have none, I might have to wait until I can get my hands on one of them.

In my next article, I would love to talk more about the performance of filter, but first, I forgot that the only Software Defined Radio I have in hand is the old MCX connector. I would have to wait for my order of NESDR SMArtee v2 to arrive. D’oh!

While I wait for the NESDR SMARtee v2 to arrive, I will be writing the plans for what I’m gonna do with the SMArtee, LaNA, and Flamingo+ FM.

Kategori
Radio

Installing GNU Radio and RTL-SDR on ElementaryOS

This is another GNU Radio and RTL2832U Software Defined Radio tutorial based on the article I did on Ubuntu 18.04. ElementaryOS is one of Ubuntu based operating system. The ElementaryOS is designed to be easy to use and the user interface is a lot like the macOS. This ElementaryOS GNU Radio installation tutorial is made for people who just started using Linux so they can transition painlessly to using Linux for RTL SDR and GNU Radio purposes.

Installing the GNU Radio and GNU Radio Companion

Installing GNU Radio and the GNU Radio companion is as easy on ElementaryOS as it is on Ubuntu 18.04, all we need is to access the gnuradio package from APT.

# apt install gnuradio

The package installation takes a while, after finishing the GNU Radio 3.7.11-10 is finally installed on the computer. You can access the GNU Radio Companion program via Terminal or via Application Launcher.

$ gnuradio-companion

Now, we can use GNU Radio and the GNU Radio Companion, the next step of this tutorial is to install the RTL SDR package to use with GNU Radio. This will allow us to receive the IQ data from RTL SDR and use the GNU Radio to process the data as we need.

Screenshot from 2019-03-20 20.36.12
Figure 1. GNU Radio Companion on ElementaryOS

GNU Radio Source

As we can see on the Terminal output of gnuradio installation, the rtl-sdr driver is already installed, the only thing needed to be installed is the GNU Radio Blocks for RTL-SDR via the gr-osmosdr package. The gr-osmosdr is already available in the APT in ElementaryOS.

# apt install gr-osmosdr

After installing the GNU OsmoSDR module, we can access the RTL-SDR source block on GNU Radio Companion under the Sources category.

Screenshot from 2019-03-20 20-59-14
Figure 2. RTL SDR Source on GNU Radio Companion

This concludes the tutorial on how to install GNU Radio Companion on ElementaryOS. Other Ubuntu based operating system should work the same, the APT can be used as a simple way to install the GNU Radio. However, it may not be the latest version, if you need the latest version always use the source and compile your own version by CMake.

Kategori
Electronics

Installing GNU Radio for Software Defined Radio on Ubuntu 18.04

As I mentioned previously on my Frequency Modulation Basics post, I would be taking a practical approach to explain the concept of Frequency Modulation. This tutorial explains how to install the GNU Radio on Ubuntu 18.04 alongside the GNU Radio Companion and the SDR dongle support.

Installing the GNU Radio and GNU Radio Companion

First, we can begin by installing the GNU radio package via APT, but check first if the version in the APT system is up to date. As of the writing of this article, GNU Radio on Ubuntu 18.04’s APT is on 3.7.11 and the current version is on 3.7.13.4. To simplify matters, I will use the Ubuntu 18.04’s APT version until I encounter a bug that will only be fixed on the latest version.

# apt-get install gnuradio

The package installation takes a while, after finishing the GNU Radio 3.7.11-10 is finally installed on the computer. You can access the GNU Radio Companion program via Terminal or via Application Launcher.

$ gnuradio-companion

Now, we can use GNU Radio and the GNU Radio Companion, the next step of this tutorial is to install the RTL SDR package to use with GNU Radio. This will allow us to receive the IQ data from RTL SDR and use the GNU Radio to process the data as we need.

Screenshot from 2019-03-20 09-20-40
Figure 1. GNU Radio Companion Window

Software Defined Radio GNU Radio Module

The Software Defined Radio that we will be using is the ubiquitous and inexpensive RTL2832U based DVB-T Dongles turned to Software Defined Radio. We can use the GNU Radio module developed by Osmocom. To build this GNU Radio block module, we need at least GNU Radio v3.7, which is already installed via the Ubuntu APT.

We can install the GNU Radio Osmocom SDR module from the git repository of osmocom or via the github mirror. Before installing the GNU Radio Source, we first must install the RTL-SDR driver created by Osmocom for RTL2832U-based Software Defined Radio dongles.

RTL2382U Driver

First, we have to install any dependencies and required packages before we can build our GNU Radio Osmocom SDR module. The required packages are cmake and build-essential to make sure we can compile the source and install the module. We also need the libusb-1.0-0-dev for the SDR.

# apt-get update
# apt-get install cmake build-essential libusb-1.0-0-dev

Then, we have to clone the repository, save the cloned repository in the desired place, for example we can put it on the Downloads folder

$ cd ~/Downloads
$ git clone https://github.com/osmocom/rtl-sdr.git

After cloning the repository, we can begin installing first by creating the build file and compiling the source via CMake. After compiling, we can install the rtl_sdr. Use the following commands on the Terminal:

$ mkdir build
$ cd build
$ cmake ../ -DINSTALL_UDEV_RULES=ON -DDETACH_KERNEL_DRIVER=ON
$ make
# make install
# ldconfig

Make sure to have both the build options INSTALL_UDEV_RULES=ON and DETACH_KERNEL_DRIVER=ON. UDEV_RULES is needed to access the dongle as non-root user, and DETACH_KERNEL_DRIVER will detach the default kernel driver for the RTL2832U DVB.

GNU Radio Source

After installing the RTL SDR driver, we need to install the GNU Radio Source module that is provided also by Osmocom. We can also install this automatically via APT-GET since we don’t need  to change any build configuration, use the following command to install the gr-osmosdr package:

# apt-get install gr-osmosdr

After installing, we can access the RTL SDR source on GNU Radio Companion menu under the Sources category.

Screenshot from 2019-03-20 10-58-43
Figure 2. RTL-SDR Source on GNU Radio Companion

That’s it for today’s tutorial, we will explore more about GNU Radio and RTL SDR when I have finished my Frequency Modulation basics series and we will demonstrate the analysis of a real narrow-band and wide-band FM wave on SDR + GNU Radio Companion.