[time-nuts] HP 8568B
alex at pcscons.com
Sun Jun 29 07:08:12 EDT 2014
yesterday there was an other response too he had a good suggestion
follow up with that also, set the marker on the carrier and count the
markers frequency, I wil power up my one I have a 8563 and will watch
how it is behaves and let you know
On 6/28/2014 7:25 PM, Hui Zhang wrote:
> 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" <alexpcs at 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
>>> 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
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>> 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
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