www.glkinst.com/test-equipment/manuals/Tracor*900A*.pdf
On Fri, Aug 15, 2014 at 4:49 PM, paul swed <[email protected]> wrote: > David > Yes I have seen various comments and documents describing MSK that way. > But have to say the tracor 900 does not use that method to establish a > reference. > Its a few opamps perhaps one side acting as a phase delay summing with the > original and hitting a BPF. all of that running at 100Hz center frequency. > Through this magic the 900 could use NAA as a phase tracking reference. > Its as if its a classic phase doubler. The documentation almost speaks to > that. > Its seriously simple. > Regards > Paul. > WB8TSL > > > > On Fri, Aug 15, 2014 at 4:31 PM, David I. Emery <[email protected]> > wrote: > >> On Fri, Aug 15, 2014 at 03:09:23PM -0400, paul swed wrote: >> >> > I had discounted it because of the lack of info and totally unclear how >> to >> > get rid of the FSK. MSK is FSK just with a very narrow shift. Also the >> > effects of the fsk on the carrier. Hmmm glad I am typing this. >> > It may be that the mark or the space is indeed exactly the true carrier >> and >> > that op amp circuit is notching out the shifted carrier. I will bet >> thats >> > the trick! >> >> >> MSK is a kind of continuous phase differentially coded PSK in >> which the carrier phase smoothly shifts either EXACTLY plus 90 degrees >> or EXACTLY minus 90 degrees in EXACTLY one symbol time - in the MSK >> variety of PSK the transmitted carrier phase never stays the same as the >> it was the last symbol time. When transmitting steady mark there are a >> series of these shifts plus 90 degrees (hi frequency mark) one after the >> other, and when transmitting steady space there is a series of minus 90 >> degree shifts. >> >> Obviously a steady negative phase shift is what is produced by >> a signal below a center "carrier" frequency and a steady positive >> phase shift by one above that frequency. Thus the isomorphism with >> filtered FSK. >> >> Effectively a QPSK (multi-arm Costas type) tracking loop should >> be able to track a MSK signal just as if it was a filtered QPSK signal >> with only 90 degree and minus 90 phase shifts each symbol time and >> generate >> a phase continuous recovered carrier. >> >> >> >> >> >> -- >> Dave Emery N1PRE/AE, [email protected] DIE Consulting, Weston, >> Mass 02493 >> "An empty zombie mind with a forlorn barely readable weatherbeaten >> 'For Rent' sign still vainly flapping outside on the weed encrusted pole >> - in >> celebration of what could have been, but wasn't and is not to be now >> either." >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
