19 March 2015 – Utility Listening, by Don, G4LOO

A typical SDR display
A typical SDR display

Don reminded members that his first talk about Utility Listening was back in 1990 when he described the Hoka Code 3 Data Mode Decoder. At that time there were about 37 or so different modes which are, for the most part, no longer used.
Since  that time, many of those who made the  transmissions have changed to satellite communications. However, now it is realized that satellites can be  vulnerable as well as costly. Slowly the authorities have been migrating back to HF communications. The use of complicated software negates some of the shortcomings of HF drop-outs and the overall result is still reliable and much cheaper. While still using satellites, having the HF communications means all the eggs aren’t in one basket.
Don demonstrated the free decoding software available and identified several transmissions using modern modes of modulation, although much of the results are encrypted.

Don's presentation
Don with SDR equipment