Hui That calibration procedure is meant to be run at the beginning of every critical measurement run and when ambient conditions change more than a few degrees.
Sent from my iPad > On Jun 29, 2014, at 11:33 AM, "Hui Zhang" <ba...@163.com> wrote: > > Hello: > I am afraid I made a dumb mistake, I ignored a calibration procedure in > the page 3 of manual, it's too front in the book so I missed it, I am very > sorry. > The procedure is: > 1, Connect CAL OUTPUT to SIGNAL INPUT 2. > 2,Press [INSTR PRESET], [RECALL], [9] on the analyzer. > 3,Adjust FREQ ZERO for a maximum amplitude trace. > 4,Press [INSTR PRESET]. > By follow these step, I adjust the curve peak in the center of horizontal > axis, and then I use my 10MHz REF and test other 10MHz source, the normal > marker read is 10.000001Mhz - only 1Hz error. It's very good result. > I think it a basic calibration procedure, but I never did it before, it's my > dumb mistake. Before I do these adjustment, I almost ready to pull down the > 10811 OCXO to make some separate calibration and test work. But it seems > unnecessary if I only use EXT REF. But I still decide do some calibration > work of that 18011 OCXO at late times. > At last I'd say many thanks for this group, and every kindly people who > trying to help me, thank you! > > > Hui Zhang > > > > > > > > > > At 2014-06-29 10:30:20, "John Miles" <j...@miles.io> wrote: >> Are you using the normal marker or the frequency counter marker? The >> counter marker should be accurate, while the frequency displayed for the >> normal marker position will not be. You may be able to improve the normal >> marker's accuracy in narrow spans if you run the shift-W self-calibration >> routine but it will never be as good as the counter. >> >> -- john, KE5FX >> >>> -----Original Message----- >>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On >>> Behalf Of Hui Zhang >>> Sent: Saturday, June 28, 2014 6:49 PM >>> To: Discussion of precise time and frequency measurement >>> Subject: [time-nuts] HP 8568B >>> >>> Hello all: >>> Rencently I bought a second-hand HP8568B Spectrum Analyzer, it kind of >>> vintage but works well. Only problem is its time base lost accurate. When >> I use >>> it measured my HP Z3801A output (locked to GPS), the center frequency read >> is >>> 9.999912MHz, about 88Hz diffrence. So I decide to use my Z3801A for its >>> external reference. When I connected the cable and set the reference >> switch in >>> rear paneal to EXT, the CRT displayed "EXT REF", I believed it worked. But >> when >>> I use it measure a nother GPSDO (Trimble ThunderBolt locked to GPS), it >> still >>> have 42Hz diffrence. I am very sure both of my two GPSDO is good, if I use >> my >>> HP53132A counter to compare them they will has less 1E-10 (1mHz) >> diffrence. >>> And then I tie a BNC three-way connect from my Z3801A, one way to 8568B's >>> EXT stand input, one way to the signal input in front panel, the >> diffrence is still >>> 42Hz - it's 10.000042MHz. I was fully confused, do I need a calibration >> after I >>> used external 10Mhz stand? I read the manual again but not fou >>> nd any infomation about how to do it. What do I do now? Anyone give me a >>> suggestion? Any infomation will be appreciate. >>> >>> >>> Hui Zhang >>> _______________________________________________ >>> 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. > _______________________________________________ > 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.