Frequency Response

[silv3rstr3]

I was hoping someone could explain to me why this works this way.  I don't understand why some spectrum analyzers seem to auto peak and some don't.  The majority of the ones I have calibrated will sweep all the bands without having to manually peak anything.  But the one I'm working on now is all over the place and requires me to manually peak it at several frequencies to level it out.  Am I missing something here? 

[Top Gun Test]

Hi
This would be a Sphere issue of the YTF in the RYTHM causing this .
If the alignment for the Flatness does not hold then the YTF requires
physical retuning of the 4 spheres in 4 different AXIS .
Basically the YTF Filter is double peaking so the flatness of the filter
is over 2DB causing a issue . Very common problem with these RYTHM's
and basically you have a OVEN with spheres in it aligned in a tight space .
Real headache to retune physically and is a black art . Don't try this alignment
it can cause a real headache . The Preselect peak doesn't know exactly where
on the filter to peak when its a Horrible  Filter  that has shifted and is not flat .
Its a real issue that will effect , DANL also . The filter needs to be optimized to meet
Amplitude and Flattness of the filter lobe . Hence Ripple/ AKA flatness of the Spec An
and DANL aka Noise Floor of the Spec An . Ripple is the YTF double peak +- with in
the given BW of the lobe . It should be less than +- 2 DB for a general check . Very
confusing Topic but that's it in a nutshell .

[silv3rstr3]

Well thank you for the break down!  I knew there was something wrong with this spectrum analyzer.  I don't have a parts unit to pull one out of and Keysight no longer sells parts for 8563's.  Can I limit the calibration to manually peaking signal before taking measurement?  Or should I try to get it repaired?

[silv3rstr3]

I actually found a vendor that rebuilds YIG units in SoCal so that works out great!!  Thanks again!!

[Top Gun Test]

Silv3rstr3
Yep it should be a retune for you and not a repair .
But there are a small amount of people whom can do
this alignment of the spheres . I wouldn't try personally
due to the mesh over the Sphere Cage and just the headaches
of learning this ART and the time involved . It doesn't make
financial sense , I have analyzed the way to tune it and have
tested the theory's and have been able to verify the Filter response
and know whats good, bad and marginal . But wow what a hassle
to even think about tuning these . Im glad that I could at least
shed some light on it for you ...