On Sun, Jul 9, 2017 at 10:55 AM, jimlux <jim...@earthlink.net> wrote:
> On 7/9/17 10:27 AM, Bob kb8tq wrote: > >> Hi >> >> People *have* been known to sort MiniCircuits parts and use the “extras” >> in >> something else. A certain major oscillator manufacturer once bought a >> bunch >> of RPD-1’s , sorted them for the “one in a hundred” examples, and then >> returned >> the rest for credit…… Somehow I doubt HP didi it quite that way. >> >> > Some manufacturers will cherry pick for you. Maybe the datasheet says > gain is 14 to 18 dB, and you order a batch that you want to be 15.5-16.5 > dB.. They'll pick those out, but of course, now the remainder have a hole > in the distribution. Particularly when you're buying high-rel or space > grade, where they have to 100% test anyway. Right, but there is nothing to indicate there is anything special going on in this case. The theory of operation section of the manual states that the splitters provide "nearly" in-phase and "nearly" out-of-phase signals without defining "nearly". It does not sound like it's critical and to me, it sounds like they are acknowledging that there are phase mismatches through the splitters. Then going on to the other link I posted: http://www.g8wrb.org/data///HP/Better_than_100_ps_Accuracy_in_HP_5370B_Time_Interval_Measurements_Through_Bias_Error_Reduction.pdf It accounts for the individual delays through the splitters/cables and shows how they are eliminated by doing multiple measurements and solving the resulting simultaneous equations. Indeed, the programs in the J06's manual mention that 'cable' mismatches (presumable phase mismatches) are included in the calibration constants and the same cables should be used for doing actual measurements: (the formatting did not survive and I fixed some obvious OCR errors) 40 ! THIS PROGRAM EXECUTES THE CALIBRATION ALGORITHM DESCRIBED IN D. CHU'S 50 ! PAPER "CALIBRATION OF SYSTEMATIC ERRORS IN PRECISION TIME-INTERVAL 60 ! COUNTERS", INTERNATIONAL TEST CONFERENCE, PHILADELPHIA, 1985; 70 ! 80 ! SET-UP PROCEDURE 90 ! 1) CONNECT A PULSE SOURCE TO THE INPUT OF CALIBRATOR, 3 DB LARGER 100 ! THAN THE DESIRED SIGNAL TO BE MEASURED AND APPROXIMATELY THE 110 ! THE SAME RISE/FALL TIMES, -50% DUTY-CYCLE, STABLE 1 TO 100 MHz. 120 ! 2) CONNECT A PAIR OF CABLES FROM CALIBRATOR OUTPUTS A & B 130 ! TO COUNTER START & STOP INPUTS RESPECTIVELY 140 ! (NOTE: CABLE MISMATCHES ARE INCLUDED IN THE CALIBRATION CONSTANTS, 150 ! AND SAME CABLES SHOULD BE USED LATER FOR DOING MEASUREMENTS; 160 ! ALSO "CABLES" INCLUDE LINEAR, PASSIVE OR ACTIVE PROBES) 170 ! 3) SET COUNTER TO SEPERATE: DC/50 ohms/Xl/PRESET to BOTH CHANNELS 180 ! 4) HPIB ADDRESSES: COUNTER-707, CALIBRATOR-705 190 ! 5) CONNECT A PRECISE OFFSET VOLTAGE SOURCE TO THE OFFSET INPUT: ENTER 200 ! THE EXACT SAME VALUE WHEN PROMPTED. DEFAULT IS 0.00 VOLT _______________________________________________ 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.