On 23 May 2008 at 12:48, Bob Macklin wrote: > > In my day (the 60's) spectrum analyzers used a swept oscillator into an IF > amplifier and then > through aconverter to baseband. We did not have computers capable of doing > the display by the > FFT process. > > My plan is to use the sweepable oscillator to oscillator to provide the LO > for the first converter and > convert the signal to baseband in the external box. The computer will be used > to convert the audio > input to the spectrum or scope display. > > I can write an application that would run the sweep oscillator from the PC > and display the result on > the PC. But this is not a simple piece of hardware like the simple SD > receivers I know about. > > Bob Macklin > Seatle, Wa. > Seems like you could take a pair of mixers fed by an Si570 with the output of the mixers going to the sound card. The LVDS version of the Si570 is good for 1 GHz +. You would need some switchable filters. A Softrock would work if all you are interested in is HF. Have the PC program the Si570, do an FFT on the audio from the soundcard(similar to existing SDR programs), then step the Si570 by something less than 1/2 the soundcard sample rate, and repeat. Then gather all the FFT's and write a plot program.
Dave - WB6DHW <http://wb6dhw.com>
