Howard Long G6LVB shows the embedded DSP board

Software Defined Cross Band Linear Transponder

Howard Long G6LVB produced one the highlights of the 21st AMSAT-UK International Space Colloquium with his presentation on the 435 to 2401 MHz Software Defined linear transponder (SDX) that AMSAT-UK are producing for the European Space Agency (ESA) SSETI ESEO satellite.

It makes use of the STELLA Software Defined transponder developed by Howard and demonstrated in July 2005, at the AMSAT-UK Colloquium using a PC and Soundcard.
It overcame the dynamic range problems that had, until then, bedevilled cross band linear transponders. It also provided an effective means of reducing the effects of interference from radars which operate in the Amateur UHF and Microwave bands.

Since Howard’s presentation last year, three High Earth Orbit (HEO) satellite projects have decided to use the system – ESEO, P3E and Eagle.

Amsat-UK's prototype 435 to 2401 MHz Software Defined linear transponder on display

The original prototype system made use of a PC and soundcard, not very practical for space flight. Howard has now produced a low power consumption embedded DSP board which can be flown on satellites.

This was first publicly demonstrated at the 2006 Dayton Hamvention where it performed flawlessly for 3 days. The embedded DSP board will support a transponder with a bandwidth of up to 192 kHz.

At well as satellites use this system clearly has application for terrestrial cross band linear transponders operating in the microwave bands with an input at UHF.

For more information on STELLA see
http://www.g6lvb.com/Articles/stella/

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