Pete, > > > 5. Mini-circuits BLP-1.9 low pass filter.
terminating the mixer if output with an lowpass/bandpass filter and NOT with an diplexer is not so good an idea. Where does the rf go? Best regards Ulrich Bangert > -----Ursprüngliche Nachricht----- > Von: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Im Auftrag von Pete > Gesendet: Sonntag, 24. Juni 2007 03:38 > An: Discussion of precise time and frequency measurement > Betreff: Re: [time-nuts] ? phase comparison or other device > > > Here is a scheme that seems to work well for comparing stable > frequency sources in the range of 10 to 100 second > measurement intervals. > > Objective - Measure frequency to +/-2E-12 in less than 1 minute. > > Method - Heterodyne DUT output to 1KHz with a master > reference source + > mixer feeding a tuned zero crossing detector > + counter. > > Equipment - 1. Master reference source at 5 or 10 MHz, e.g. > "mature" OXCO or > GPSDO. > 2. Synthesizer set to DUT - 1KHz, locked > to reference > source. The synthesizer averaged > output must settle > to > 10uHz in 10 seconds, e.g. HP 3335A or 3336C. > PTS 040 should work fine, also. > 3. 9 digit/s counter, locked to reference > source with > selectable gate time. An input LPF > (100KHz) helps, > e.g. HP 5335A. > 4. Mini-circuits ZRPD-1 mixer. Other > level 7 mixers > should work, but haven't been tested. > 5. Mini-circuits BLP-1.9 low pass filter. > Other filters > should work, but haven't been tested. > 6. Tuned zero crossing detector, accepts > 0 to 5dBm 1KHz > sinewave input & outputs 1KHz > squarewave to counter > with less than 1nS rms jitter. > > Setup - DUT set to +7dBm connects to mixer LO port. > Synthesizer set to DUT - > 1KHz at +4dBm connects to mixer RF port. BLP-1.9 > connects to > mixer IF port. ZCD input connects to BLP-1.9. > Counter connects > to ZCD > output & set for 5 to 10 second gate time. The > DUT frequency = > synthesizer setting + counter frequency; > 10uHz digit = 1E-12 for 10MHz DUT. > > The ZCD - Made from 2 Analog devices ADA4899-1, inverting > configuration, > cascaded, using +/- 2.5 volt power > supplies. Both amps > have their > non-inverting pins connected (only) to a > 100 ohm resistor > to ground. > Both amps have 5uF//5mH to ground on their > inverting > inputs. The > input amp has Rin = 422 ohms and Rf = 6190 > ohms. The > output amp > has Rin = 562 ohms and Rf = open. The > output amp output > pin has > 2ea 100 ohm resistors in series to ground. > The counter is > connected > to the common point of the 100 ohm > resistors. Nominal > supply bypassing > is required. Battery supplies at +/- 3 > volts help isolate > noise sources. > > Only 2 ZCD parts aren't junk box items. The Analog Devices > ADA4899-1 are in distributor stock as SMT parts only. The 5mH > inductors are hand wound on MPP toroid cores. 133 turns on a > 55438 core or 114 turns on 2 stacked 55521 > cores > using 22 or 24 AWG wire work fine. Other MPP cores will work, > but limit Bmax to 50mT at 1KHz & 0.5V rms. Gapped ferrites > are too noisy. The 5uF caps are polypropylene or mylar film types. > > Noise floor measurements using HP5335A opt 010 as reference > source & 1KHz counter + HP3336C synthesizer yielded Favg = > 10,000,000.000 001 5 Hz and Fdev = 4.3 uHz for 36 samples at > 5.7 second gate time per sample. 10 sample groups are within > +/- 2E-12. > > Pete Rawson > > > > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts > _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
