20 Sept. 2012- The Software-Defined HF Receiver

We had a very good turn out for our meeting including visitors from Cambridge, St. Neots and Huntingdon increasing our usual total.

We heard an overview of the company and their products and their users.

Software defined receivers have come a long way in the last few years and the unit of most interest was the G31DDC ‘Excalibur’ which, although expensive, was within the range of the amateur market. It is described as a high performance, direct-sampling, software-defined short wave receiver.

The frequency range runs from 9 kHz to 50 MHz which includes a real time 50 MHz wide spectrum analyzer with a 2 MHz wide instantaneous bandwith available for recording, demodulation and further digital processing.

The only downside that could be noted was the lack of RX/TX switching for those who would be using it with a transmitter on the same antenna, as most radio amateurs do. It transpires that even the smallest whiff of RF into the receiver will damage the front end, rendering the entire unit next to worthless since the building technique does not allow easy access to components.  Having said that, the receive facility is very impressive.

13 Sept. 2012 – Welcome Back and Project Check/Test

The first meeting of the new season saw members a bit thin on the ground, but those who did attend welcomed two visitors and then saw a demo of a commercially produced Noise Canceller under test.

Ian, G3ORG and Richard, G3NII had set up a signal generator and a spectrum analyzer to see just how much a signal could be eliminated.  The result was not all the way to zero, however, Ian then set up his own model of the  Club Project, The SADARS Noise Eliminator, which cost about a tenth of the price to build and that showed the signal being completely eliminated!  There were nods of approval all around. The group’s attention was then drawn to the one I had built.  A cheer went up when it also showed the complete elimination of the signal.  (to my great relief).

The success of this Club Project is due to the effort and expertise shown by Richard  (development) and Ian (testing) .Well done! and Thank you on behalf of the members who built the project.