Hi Hui... The first thought is that you are tied to the resolution of the span divided by the number of displayed points -1. Try a narrower span. If you look at the absolute accuracy spec that error may be within the '66's capability.
Also, I believe there is a marker counter function that will give you a more accurate reading. Another consideration is that not all of the internal LO's are locked to the 10 MHz reference. Don't panic yet :) >From Tom Holmes > On Jun 28, 2014, at 9:48 PM, "Hui Zhang" <[email protected]> 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 fo u > 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 -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ 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.
