Hello Alex: Thanks for you quickly reply, yes I use same source as EXT reference and input signal, it also has 42Hz error. Do you mean even I use EXT reference the intenal 10Mhz time base still need work? If so, I really need calibrate and readjusted it (HP 10811).
Hui Zhang At 2014-06-29 10:17:22, "Alexander Pummer" <alex...@ieee.org> wrote: >On 6/28/2014 6:48 PM, Hui Zhang wrote: >> 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. >it could happen that thes ystem reports the external reference but the >time base reference oscillator doe not lock to it. To check that use >the same source fo the reference and also for he input and set the span >small few kHz the resolution 1/10 of the span and if you still see the >freq error than the spectrum analyzer internal time base 10MHz need to >readjusted since it cannot lock to the external reference, that is >normal aging that instrument may be 25 years old >73 >KJ6UHN >Alex > >_______________________________________________ >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.