Stuff I do

WSJT-X is a great desktop application for communicating via radio using various weak signal modes. I use it on the HF bands to contact amateur radio operators literally all over the world. The new 1.7.0-rc1 alpha release features a new algorithm for decoding, and it is quite a bit more effective than the previous 1.6.x versions. One of the most important parts is decoding Reed-Solomon codes. The previous versions used a proprietary decoder, this one uses a new, open-source method. Since I work a lot in JT65 and JT9 on short wave, building the new version definitely worth the struggle.

In this chapter I'm going to show you how to build an atmospheric ion chamber for detecting radiation. The detector will have little drift, can be set to zero, and can be used to compare the radioactivity of samples, measure weak sources, or follow the decay of short half-life sources for hours or days even. These features all require that the detector to be stable, and the readings don't drift around with temperature. Temperature drift is very likely the worst offender to our previous ion chamber design, so we're going to deal with that one this time.

Theano is a Python module that enables one to construct mathematical expressions with matrices and/or tensors (basically more than 2 dimensional "matrices"). These expressions are than can be evaluated using Python, but Theano can translate the expression into a C program and compile it to binary. This way it can achieve respectable performance. But wait, there's more! Theano can build the program so certain - or all - parts of it run on a GPU. Yes, on your video card. Modern cards can do calculations in a way that makes them especially fit for doing linear algebra and similar operations. In "similar" I mean the execution of simple operation on lots of data in parallel. A GPU-s can be several (tens or hundreds of) times better, than your CPU. I'm going to show you how to exploit an NVIDIA GPU, using Python.

The detector will consist of a tin can, two transistors and a DVM. I will also show how to improve and stabilize the basic circuit by adding an extra transistor and an identical "dummy" circuit to cancel leakage current and temperature dependence.

The ADIF file format is a simple way to store and organize Amateur Radio (or HAM Radio) log data. It is a way amateur radio operators most frequently store their records on the contacts they make (probably after paper). (For fellow HAMs, my callsign is HA5FTL, see my QRZ.com page for a description of my station and yours truly, and for contact information, if you wish to express your objections and/or approval of one or several of my points made in this article.) I have to start with a disclaimer.