Friday, May 22, 2009

30m QRSS-RX/MEPT

The plans to join the 30m-MEPT and the 30m-subharmonic receiver are on hold for today, since I believe that some of the ideas or not quite there yet.

You may have seen, that I used a 5068.8kHz crystal as modulated mother oscillator for the MEPT. An active doubler gets the signal into the 30m band, followed by a 10140kHz crystal as filter.

As I mentioned earlier on the KnightsQRSS mailing list, having a mother-oscillator running all the time could be done by switching on an active frequency doubler to TX and deactivate it for RX, thus, not prominent carrier will be present in the 30m band. One requirement to me seems, to build an oscillator that creates as few as possible harmonics. That seems to rule out all HCT/HCTTL-approaches completely. The only way of using the product of a digital oscillator that I can think of, having a second 5068.8kHz-crystal as filter in the output of the oscillator and reaaaallly carefully wrap the thing up into something RF-tight. I guess, it will still be easier and less cumbersome to build a clean oscillator from discret components.

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