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Security (anti-spam) Question: How many dits in 72?
Fri, 09 Mar 2007 19:21:00 +0000
This circuit is a basic single balanced diode mixer, as seen in SSDRA and EMRFD. The most critical part seems to be the diplexer components (C1, C2, and L1). Due to contest limitations, I could not get ideal values for these components, but I think I have found values that work fine for this application. Using my PIC-EL/DDS-30 as the BFO and a XTAL osc as the IF source, the detector worked well when connected to the rest of the audio chain which I have developed. I also learned that the class AB amp really puts out some power into headphones. Attenuating the XTAL osc produced a much more pleasing tone on my second test of the detector. I will be adding the BFO circuitry to this schematic later. -Jason, NT7S 30 Nov 2006 The BFO is now working more or less as I would like. The design is the basic Colpitts oscillator seen in many other homebrew rigs. Since trimmer caps are pretty scarce, I`m trying to see if I can get away with using fixed value caps. A bit of substitution showed that 56 pF worked pretty well for the output tank circuit (C4). I`m not totally sure that C5 will stay at 10 pF, but it is close enough for now. The output of the BFO is +10.5 dBm, more than enough to drive the product detector. - Jason, NT7S 3 Dec 2006
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