LibreOffice: bibliography management with JabRef

LibreOffice Writer is a powerful text editor with a nice bibliography management. Yet, not very user-friendly. For example, if you want to insert a bibliography entry in a document, you are presented with a list that contains only the short name of the reference, making it difficult to use large databases. Moreover, each database entry must be manually inserted into the database.

But with the help of the bibliography manager JabRef, things get more simple. It uses the BibTex file format, so the bibliographical databases made with it are compatible with LaTeX. It has a nice online search tool which can populate a bibliography entry with all the information based on ISBN for books or document ID for different papers. And most important it integrates with LibreOffice and OpenOffice, allowing users to insert a bibliography entry with a simple two-click operation.

Dual booting Windows and Ubuntu [MBR]

Linux distributions are becoming more and more popular. But before completely giving up Windows, many users want to have both OSes on their PCs. That's because they can't find an alternative for their everyday apps on Linux or can't play some games. Several manufacturers also started to sell preinstalled Linux computers. Before wiping the whole HDD to install Windows, consider dual booting.

This post will give solutions to some common situations. Because Ubuntu is one of the most popular Linux distributions, it will be used during this tutorial.

Here are some common situations that we will talk about:

ScanTailor Fix DPI dialog

ScanTailor is a scan post-processing software that can improve significantly your scans and reduce the file size of your e-books. But it needs high quality scanned images above a threshold considered by it 300 DPI. The purpose of this post is to understand the Fix DPI dialog in ScanTailor. If you don't see it when loading images everything should be OK and you can continue processing.

The Fix DPI dialog

How to identify an unknown radio tuner

Radio frequency tuners can be found in a lot of devices, starting with TV sets, set top boxes and PC tuner cards. A tuner is a device that takes a ”chunk” of a frequency carrier of a bandwidth, amplifies it and then shifts it (usually by down-converting) into a fixed frequency that will be fed into a demodulator device. Tuners are difficult to build and a DIY tuner will never have the performance of one from a radio receiving device. The RF signal enters a baseband amplifier. Further, this signal is mixed with a local oscillator with variable frequency. The result exits the tuner as Intermediate Frequency (IF). Sometimes the tuner also contains a filter at the IF output. These functional blocks can be integrated into a superheterodyne receiver with ease (just add a detector). So, what can you do with a tuner? Keep reading.

Gray-Hoverman, the wideband TV antenna

In the past, air TV channels were broadcast on frequencies ranging from 170 MHz to 860 MHz. The VHF-Hi band covers 175 to 230 MHz, while UHF covers 470 to 860 MHz. This is a large interval, covering two bands and it is difficult to receive with a single antenna. But, nowadays the UHF band for TV broadcasts is getting smaller. Frequencies starting from 600 MHz are being repacked for mobile networks.

The Gray-Hoverman antenna has been designed by Doyt R. Hoverman and it was patented in the sixties. It only covered the lower part of UHF, from 470 to 720 MHz (21 - 52 channels). If that could have been a problem, it's not anymore. The average gain in this frequency range is 13 dBi with reflector and 9.2 dBi without it. With some additional elements, this antenna can also receive the upper part of VHF from 170 to 230 MHz, with an average gain of 8.1 dBi with reflector and 6 dBi without it. The overall gain is not too much but, since it is easy to build and wideband it's worth a try. The original design has been republished and distributed according to the GNU GPL version 3 license.

Infrared protocol analysis with PC soundcard

Infrared communication is widespread among electronic devices that use remote controls. Because of this, there are more protocols in use and the data (bytes) sent to the device depend on manufacturer. This post will show you how to view the waveform of an infrared signal emitted by a remote control, how to analyze and decode it. Then it will be possible to reproduce it. In this way you can program your universal remote control or your mobile device (smartphone with IR transmitter) with the right code for the best results.

Instead of using an oscilloscope for signal analysis, due to the low frequency of the IR bit stream, an ordinary sound card will be used to view the signal. The signal is amplified, filtered and demodulated by the IR receiver, so only the bit stream is sent to the sound card input. This is sampled at the usual audio rate and displayed in various software tools.