Hi You can do the 14 db deep modulation with a tristate gate and a pair of resistors. Ground the input and feed the “modulation” signal to the tristate control.
Bob > On Aug 25, 2018, at 4:35 PM, paul swed <paulsw...@gmail.com> wrote: > > From the earlier threads OOK modulation does not work for high end clocks > like spectracoms and truetimes. Have not tried it on the cheapy clocks yet. > > I added an external modulator. A dg419 analog switch and then with a few > resistors added DC offset and anttenuation so that the carrier drops by -14 > db per the wwvb spec. The logic control is driven from the chronverter and > it totally works. Spectracom Netclock 2 locked up in the normal time. > There are far better modern single supply analog gates that will work. Just > did not have any. > > The 60 KHz carrier is supplied by a fluke 6060 generator. This eliminates > any chance of being off frequency and is not the long term answer. > > The chronverter actually uses a dallas semiconductor clock chip thats > reasonably accurate.(dangerous to say on time-nuts) So that even if you do > not add the GPS receiver it will run quite some time correctly after > setting the time. > > Chronverter draws 6 ma from a 5 V supply. I always like low power. > > All in all a very nice answer to what do we do if WWVB goes away. > As mentioned it handles timezones and DST and you can change DST if those > silly politicians screw with it again. > > Speculation > The chronverter actually puts out carriers for the popular LF stations > along with the time codes for them. > > Though the modulator allows quality clocks to lock I speculate the > frequency from the chronverter is not tight enough. All of these clocks > have very sharp crystal filters in them. 10 Hz. Plan to measure the output > of the chronverter see what the 60 KHz is actually at. Though listening on > a HP3586 receiver it appears pretty close to frequency maybe its just not > good enough. Or the fact is OOK modulation does not work because it gaps > the PLL in these clocks. > > Next steps > > - Determine and lay to rest the OOK/need for external modulator. > - Power amplifier and loopstick transmitting antenna staying at or below > 30uv@30 meters. > - Integrate a neo6 GPS receiver in. (Seriously easy) > - > - Box it up. > > Have my eye on one of the Truetime DC468 units and the classy panelplex > display. > > Hope this helps those of you concerned with what to do should WWVB go away. > Regards > Paul > WB8TSL > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
