); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY [EMAIL PROTECTED] wrote: > > > The Idaho State University version is reported on their web page for the > project as having been checked over a 13 day period, by the Idaho National > Laboratories Calibration Lab, and found to be accurate to 1.2x10^-10. > > > regards > > Nigel > GM8PZR > Nigel
The Idaho state project http://www.geocities.com/isurflab/Frequency_STD_Project.html Has the usual hallmarks of inexperience, fine for student educational purposes but shouldn't be slavishly copied without understanding. As usual the measurement technique and conditions used for the frequency comparison are poorly documented. Using an OPA2705 opamp as a comparator to produce a 5V logic level output from the GPS receivers PPS pulse is probably an effective way of adding jitter to this signal. Even using an RS485 line receiver as used on the original VE2ZAZ <http://www3.sympatico.ca/b.zauhar/GPS_Std/GPS_Std.htm> board is probably a better choice despite its built in input attenuator. Even a saturated switching transistor probably has better performance than the opamp. Add a simple baker clamp to the transistor and the performance is probably hard to beat for the outlay. Alternatively a 74HCT14 or 74ACT14 would also work well as a 3V to 5V level translator. Using a switchmode power supply from a PC isnt exactly conducive to low noise. Bruce _______________________________________________ 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.
