Spectrum Analyzer Noise Floor Rise at 2.9GHz - Is it Normal?

[Electro Fan]

Just checking to see if it is normal for an HP8561E (9kHz - 6.5GHz) to have a noise floor rise at about 2.9GHz?  If so, how much?  3dB?  Less?  If it's normal (or not), is there a way to minimize the step up?

[KE5FX]

Yes, it's switching bands internally.  The IF gain has to come up a bit to compensate for the extra front end loss of the preselector.

[Electro Fan]

3dB is ok?

[KJDS]

That looks normal to me.

[MadTux]

Harmonic mixer in action. I'm not exactly sure why that happens, but I think it's because the higher harmonics have less power than fundamental, so less mixer driving signal => more noise. The 1th mixer sees fundamental and all harmonics at once, since the frequency selection only happens in the front end (YIG tuned filter).

Anyway it's usually a sign that the SA works as it should. See 8566 as example, it uses baseband, 2th, 3th and 4th harmonic, thereby 4 steps in 2-22GHz sweep:
http://www.sglabs.it/public/SgLabs_HP_8566B_1.JPG

[TheSteve]

Looks pretty normal, here is a full sweep with an 8563E:

[Electro Fan]

Harmonic mixer in action. I'm not exactly sure why that happens, but I think it's because the higher harmonics have less power than fundamental, so less mixer driving signal => more noise. The 1th mixer sees fundamental and all harmonics at once, since the frequency selection only happens in the front end (YIG tuned filter).

Anyway it's usually a sign that the SA works as it should. See 8566 as example, it uses baseband, 2th, 3th and 4th harmonic, thereby 4 steps in 2-22GHz sweep:
http://www.sglabs.it/public/SgLabs_HP_8566B_1.JPG

Yes, I noticed it is fairly pronounced in various photos of the 8566 - that made me feel better since I think that is like the Daddy or Grand-Daddy of the 856XE series