Advantest R3273 spectrum analyzer problems with high spans

[lowtension]

Hello,

I have  a R3273 with a problem displaying signals above the low band mixer 3.5Ghz with high spans over about 10 Ghz.
For example, trying to detect a CW signal -10dbm at 12 Ghz on full span , signal is not detected at  all on some sweep  or has low amplitude on another sweep or has almost correct amplitude on another sweep (signal fluctuate up and down to noise level on different sweeps on the trace) , switching  down to 10Ghz  or less, signal detected correctly with correct amplitude.
Changing sweep time up or down does not help. Also, changing the YTF offset values does not help either, just under about 10Ghz span works fine.
Any clues what can tha be ?
Thanks
 

[eb4fbz]

Check the YTF and YIG cover screws, they usually get loose over time.

[Samogon]

Did you run calibration? Just in case?

[lowtension]

Hello,

I checked the YIG and the YTF, screws are 100% tight. Calibration does not help.
But I noticed that on higher RBW like 5Mhz at higher span 10ghz- 26.5 Ghz, the problem does not exist!

May be it is normal if I need to identify a signal in large spans, I need to change the default RBW from 3 MHz to 5 MHz.

Also, YTF is tracking great at all frequencies.

Is this normal behaviour ?

Thanks

[Samogon]

I have R3172, let me reproduce.

Pretty stable on mine, but accuracy is degraded and it is normal on such big span imho.

[lowtension]

I have R3172, let me reproduce.

Pretty stable on mine, but accuracy is degraded and it is normal on such big span imho.

Mine jumps somtimes down 5-10 dbm on some sweeps, on other sweep can dissappear, stable also in some other sweeps. Very wierd. at 5 MHz RBW looks stable and correct amplitude. It seems that the YTF is missing with 1-3mhz and on RBW 5 MHz this fault is not noticable because of the wide rbw.

I will try to look at the output of the amplifier stage of the YTF tune turrminals using a scope.
Thanks for showing this.

[lowtension]

Checked again,  I was wrong in the first post, even under 3.5Ghz problem exists in wide spans over about 10Ghz. It is not the YTF.

So, what I we have here something to do only with wide spans and not related to the YTF enabled above 3.5Ghz, any ideas? thanks

[Samogon]

Stupid question: do you have preamplifier disabled?

[lowtension]

Stupid question: do you have preamplifier disabled?

Hello,

No preamplifier option in this unit.
Thanks