Free EDA: Design and simulation with LTspice

This is the first part of a series articles about turning a circuit idea to design using only free software. EDA stands for electronic design automation and Wikipedia has a nice comparison table of software for this job.

Before drawing the schematic and designing the PCB we need a circuit idea. Then we will use the free circuit simulation software LTspice to simulate our design. This is what this article is about. LTspice is developed by Linear Technology and it runs native in Windows and Mac OS X. The Windows version runs without issues on Linux using Wine.

This is not a LTspice tutorial. For that we recommend Terry Sturtevant's and Simon Bramble's tutorials. You will also need electronics knowledge. See All About Circuits, Learn Electronics Online or Learn About Electronics.

Make a wideband antenna matching transformer

Most do-it-yourself TV antenna projects I could find use a readymade impedance matching transformer between antenna and cable. But what should you do if you can't find one at your local supplier? Let's attempt to make one with nothing more than some copper wire and a ferrite core. You could use some hard to find double hole pig-nose RF ferrite cores, but this transformer performed fairly good with ordinary toroidal cores.

This matching transformer can be used for VHF and UHF reception (from 50 to about 800 MHz). The input is 300 ohms balanced and the output is 75 ohms unbalanced, ready for coaxial cable connection. I found out that a device similar to what is presented here is used in commercially available antenna preamplifiers with 300 ohms input.

UEFI NTFS: Bootable Windows USB from Linux

Installing Windows from USB drive in UEFI mode requires a FAT32 formatted USB drive. How to create that bootable USB is described in Make a bootable Windows USB from Linux (Ubuntu). However that method is unusable in some cases where install.wim is larger than 4 GB.

The procedure that is about to follow should work with any Windows version that supports UEFI boot (Windows 7 on 64 bits and all the newer versions). It has been successfully tested only in VirtualBox but it should work on real hardware too.

We will make two partitions on the USB drive, one that is FAT32 and will hold an EFI bootloader and the other is NTFS and holds Windows installation files. The bootloader will use a NTFS driver to read the NTFS partition and boot Windows.

Change mouse cursor theme in Ubuntu

There are a few applications that should allow changing default mouse cursor in Ubuntu. Unity Tweak Tool, GNOME Tweak Tool, Dconf Editor fail to change the mouse cursor or do it in such a way that it uses mixed themes.

In order to have a consistent cursor theme you must select it from one of these apps and also run a command in Terminal. First, the command. This is the most important and you may not even need to change the cursor theme from those apps too.

sudo update-alternatives --config x-cursor-theme

Safely try new kernels in Ubuntu Linux

Some while ago, bothered by the ACPI PCC Probe Failed message at every boot, I decided to try the latest Linux kernel, which was at version 4.2. But I ran into troubles. So this tutorial is not focused on installing new kernels, but on the steps you should take to maximize the chances your new kernel will work and how do you prepare to restore your system to the old kernel, before actually installing the new one.

Here is what I recommend doing before trying a new kernel:

Add page numbers, headers and footers to PDF in Linux

If you need to add page numbers over each page of a PDF document in Linux keep reading. Actually using this method you will be able to add any kind of content that changes sequentially or by page to a PDF document. By content I mean header, footer and/or watermark. It can be text and/or graphics. I will use cross-platform and free software so you may want to try this on Windows too. I will be using only GUI software: Scribus, PDF Chain (the GUI to pdftk) and GIMP. You can install these on Ubuntu with:

sudo apt-get install scribus pdftk pdfchain gimp

First of all you need to gather some information about the document you want to add content to. Using your favorite PDF reader or any other PDF information software find out the number of pages and their size. In order to know where to place headers/footers pick a content representative page from the PDF document that you will later use as a template to avoid overlaying header/footer with document contents.