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 […]

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 […]

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 […]

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 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 […]

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):

I’ve started a new project: a DSP tutorial for amateur radio enthusiasts (or anyone interested in encoding/decoding FSK, PSK etc. signals). The tutorial currently contains posts about how to generate a sine wave, how to calculate FFT, determining the dominant frequency, using different filtering methods and how to generate a single-sideband signal. You can view […]

The new room of the HA5KDR radio club at the National Defense University.