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
73
KJ6UHN
Alex
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" <[email protected]> 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 n
ot
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
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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
73
KJ6UHN
Alex
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