Finally I’ve finished my old PSU’s renewal. I added overvoltage protection and a slim fan which is switched on by bimetal thermostats on the heatsinks when the temperature reaches 45°C. I bought both the slim fan and the thermostats on eBay. The overvoltage protection is a very simple circuit: when the voltage is above a preset threshold (determined by the voltage divider on the left), the tiristor opens and burns out the fuse.

I’ve finished the shiny new webpage of our radio club: www.ha5kdr.hu

Last weekend we installed Ubiquity AirGrid M5s to the Gerecse tower and my QTH in Tata to create a 5Ghz Wifi link between them. It was quite difficult to put the stuff up on the tower because the wind was blowing crazy. Link works reliably and fast, the average is around 120MBps, I can copy between the two networks with 2.1 megabytes/s. Interestingly, when it’s raining, the link and signal quality drops as you can see on the graphs below.

(The collinear Diamond X510 antenna above the AirGrid is under repair, that’s why the ground planes are missing.)

I bought this antenna on eBay about a week ago and installed it on the mast on the roof at my girlfriend’s place. Price and quality is quite good, looks like the exact Chinese copy of the Diamond X200, but I had to use some silicon paste on the connections to ensure no water could get in.

I’ve finished the new ham DSP tutorial section about SSTV modulation and demodulation.

Here’s a video which shows my decoder compared to MMSSTV:

I’m using cmus for playing music. It can call a script whenever a song changes using the :set status-display-program=/path/to/scrobbler command.

I’ve written a PHP script bundle which handles scrobbling the currently playing and played song to last.fm. It can also read the ID3 (v1 and v2) tag from the music file using the getid3 PHP library.

You should set your last.fm user and password in the status_display_program.sh file and then set cmus to use that script as the status-display-program. I’ve placed the whole stuff under /home/nonoo/.cmus/last.fm.

You’ll need php5-cli and php5-curl installed.

I already wrote about lowpass filtering using FFT in one of my ham DSP tutorial articles. The simple brickwall filtering method described there is not applicable in some cases because it introduces ringing in the resulting filtered sound.

After some research, I made an article about designing and implementing a proper FIR filter which uses FFT convolution.

I’ve expanded my ham DSP tutorial with sections describing RTTY encoding and decoding using several methods. Here’s an example video of my example encoder/decoder (FLdigi is shown for comparison):