I have seen it talked about (around the LF fraternity, but generally they are stable enough there and just need calibation) a lot but not accomplished yet.
How about injection locking the on board osc....maybe gating the feedback with the reference....note I havent tried this? Another technique I have used to shift "logic-block" oscillators is to vary their supply voltage, they will oscillate from around 3v to well over 5.5v ....that might enable you to phase lock it using a variable regulator to vcxo to crystal?? Alan G3NYK ----- Original Message ----- From: "Rex Moncur" <rmon...@bigpond.net.au> To: "'Discussion of precise time and frequency measurement'" <time-nuts@febo.com> Sent: Monday, June 01, 2009 10:59 PM Subject: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references > > Hi all > > Does anyone have any experience of locking a USB external soundcard to a > GPSDO 10 MHz reference. > > I am interested in advice on any good quality soundcards that can be readily > locked to either 10 MHz or if necessary to some other frequency that we can > derive from a GPSDO source. I have done some tests with the SignalLink > soundcard that uses a Texas Instruments PCM2904 chip and requires a 12 MHz > lock frequency. This requires some cutting of tracks to remove the internal > oscillator feedback and insert the locking frequency. 12 MHz is readily > derived from 10 MHz but I have not been able to get it to lock. The Texas > instruments data sheet suggests that it is possible to use an external > refernce but also says this is not recommended. With this expereicne I > would rather find a sound card that is designed for external locking that > does not require the cutting of tracks. > > For info the purpose of this request is that we are looking at using very > narrow bandwidth modes at less than 1 mHz for light wave communcation. To > date using LEDs and cloud reflection we have worked over 200 km with WSJT > but we should be able to do 20 dB better if we can get down to milli-Hz > bandwidths (at the expense of spending all night to complete a QSO). Our > expereince to date is that standard sound cards are just not stable to > better than 5 milli-Hz at 1000 Hz which should be readily solved by GPS > locking let us get down to sub milli-Hz levels. > > Rex VK7MO > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.