Sunday, October 29, 2017

Heathkit SB-303

This column has nothing to do with computing so far, but it might in the future. This is a Heathkit SB-303 amateur band receiver.  Great looking, isn't it?  And it is one of a line of several Heathkit ham radios. You can find here a very interesting article on the Heathkit SB line which started in the early 1960s and ran into the early 1980s.

Here is the guts of the radio. This is an all-transistor design; most of the SB radios used tubes. These were kits---this radio was built by someone who did a pretty good job.  It has also been restored by the previous owner. The large, electrolytic capacitors in the power supply tend to degrade over time and these have been replaced. The previous owner also repainted the case.

I am thinking about using one of these radios as the starting point for a hybrid digital/analog radio.  By tapping signals the signals in the radio and connecting them to analog/digital converters, I can ship them to a computer or FPGA for digital processing. Many software-defined radio rigs run at relatively low sample rates and so do most of their digital processing in the baseband.  A fancy data acquisition card could let me move the interface earlier in the radio, perhaps all the way to the first stage of amplification after the antenna. This sort of project would be a good way for me to get my hands dirty with software-defined radio; it would also be fun to compare the signal characteristics of the analog and digital versions.  All of these plans, of course, depend on time permitting from other projects and duties.  We shall see how things play out.

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