Don, Thanks for the comments. This I guess will be enough. I probably wouldn't do too much with the DSP math anyway although I have written some digital filters and playing around with FFT using signals that I invent mathematically and also some captured audio streams. But, all this was using Mathematica (Wolfram) so a lot of the heavy lifting is already done for me (e.g. the FFT and various functions for managing the data).
73, phil, K7PEH > On Nov 17, 2014, at 3:13 PM, Don Wilhelm <w3...@embarqmail.com> wrote: > > Phil, > > The sidetone is a constant audio pitch sent through the audio amplifier (once > you select the pitch you desire). It is not a function of the VFO, it is > just a constant tone. > The demodulated audio (from the signal you are listening to) does vary with > the VFO setting. > So yes, the selected sidetone pitch tells the DSP not only what spot pitch to > send, it also is used to figure out how much frequency offset to use on the > signal received as a result of the VFO setting. > > I can't give you the DSP math to produce that, but Lyle certainly could. I > suspect the demodulated signal tones and the sidetone are simply added - that > is at least the result in the analog world. I do know the BFO/signal > relationship is a "mixer" process and if I recall that in DSP math is some > sort of multiplication process - as you can tell, I am not well steeped in > DSP techniques, but I do recall a bit of signal processing math from my > college days even though that was 54 years ago and I did not use that > theoretical level of it, so much has become 'fuzzy' with time. > > Perhaps some study of DSP algorithms would help you out. > > 73, > Don W3FPR > > On 11/17/2014 5:51 PM, Phil Hystad wrote: >> OK, so side tone generator is a DSP function. But, your answer leaves a lot >> of details out. >> >> So, if I am using the side tone generator to zero beat another CW station, I >> do two things. >> One, I adjust the sidetone pitch to something I prefer. Two, for the actual >> CW station, I >> adjust the VFO until the pitch of the CW signal closely matches my sidetone >> pitch. (I know, >> I could push the spot button too and I usually do that). >> >> If this is true, then the sidetone generation itself is a function of the >> VFO frequency, that is, >> it is, say, 600 Hz away for example in a BFO kind of way. >> >> I was looking for a description of more of the details of how this was >> implemented and I admit >> it is to satisfy my curiosity. Math functions don't scare me though, I did >> my graduate work in >> Math. I admit to being a bit weaker with typical DSP algorithms -- more of >> a philistine than a >> practitioner. >> >> 73, phil, K7PEH >> >> >>> On Nov 17, 2014, at 2:16 PM, Don Wilhelm <w3...@embarqmail.com> wrote: >>> >>> Phil, >>> >>> The CW sidetone is nothing more than a set of math functions inside the DSP. >>> With the proper DSP code, you can make up most any kind of sound wanted, >>> even sidetone mixed with demodulated signals. That is what the DSP board >>> firmware is all about (plus a lot more). >>> >>> 73, >>> Don W3FPR >>> >>> On 11/17/2014 4:57 PM, Phil Hystad wrote: >>>> I am asking this question of K3 and KX3 since I am assuming that the >>>> answer is the same for both rigs. If it is different, maybe someone can >>>> let me know. >>>> >>>> Question: Is the CW sidetone generated as a separate audio oscillator >>>> circuit or is it generated from a BFO type circuit? This morning, I >>>> started thinking of this question and I realized that I don’t know too >>>> much about how CW sidetone is implemented. I am thinking it is a separate >>>> audio oscillator but I may very well be wrong. >>>> >>>> Follow up Question: If the CW sidetone is a separate audio oscillator, >>>> what is happening (details preferred) when you use the sidetone to zero >>>> beat a CW signal. >>>> >>>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to w3...@embarqmail.com > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
