Regarding spectrum analyzer

The Manufacturers data on the analyser should give you figures.

It depends what you have attached to it!

If you stick a correctly matched dummy load on it then you should see the lowest possible noise floor.

If you have an antenna then you will see the ambient noise in your environment, this can be reduced by trying other locations, just moving a few yards may make a big difference. Or use an anehoic chamber (V expensive)

But if i add a preamplifier to a spectrum analyzer will it reduce its noise floor,

I may be wrong here...but I think the answer is no.

YES

Definitely not - DEL is right. Your amplifier is a REAL amplifier and so puts its own noise to the analysers noise and the signal, so the signal/noise-ratio will be worse. The only components producing no noise are imaginary like L and C, if you have a real component (and your amplifier has, of course), you will have a current or voltage noise, depending on your amplifiers chain impedance.

The only way to reduce your analysers noise floor is -------- buying a better one.
Pardon - Uwe

Hi I call it the grass. Some times you can reduce it with special shielding but it depends on the unit.

Mr X

Depending on the quality of your Specan you can sometimes reduce the internal noise floor by checking internal shielding and grounds as they become very important to that overall noise floor of the instrument. You can however compensate for noise floor by taking an ambient measurement and factoring it into subsequent measurements. However if your noise floor is greated than your anticipated signal its time to get a new better quality specan.

if you are refering to the over all noise floor of a test set up however and not just internal noice floor shielding, shielding, shielding is the answer proper "common" grounds on the power side of the equipment used in the set up and bench etc. . .

Open her up and check the shielding, check the ground of your power source for the instrument. verify internal LO and Mixers are set to spec and it should reduce it to the optimum for this instrument - again the quality of the spec an will determine the floor overall.

hope this helps

A trick we used on Hewlett Packard spectrum analyzers back in the old days was to liberally soak the pre amp in Freeze spray. This dropped the thermal noise to a practically undetectable level and increased the sensitivity by at least 3 db or more.

Greetings,

as usual a mixed bag of answers...with some being somewhat less helpful than others
(I have a pet peeve...in cases of very complex issues, which most definitely include the subject of noise & spectrum analysis...not to pick on #5, specifically, 'cause it happens here a lot...but short monosyllabic answers aren't usually too helpful...).

tdesmit got it closest (but I like taejonkwando's idea! - I'd inquire about warranty issues on that one :-)). To answer your primary question: look in the manual, if you don't have one, call the mfr. In fact it's very very difficult to establish the absolute noise floor of anything, especially a specie... As for adding pre-amplification, as others have indicated: it will improve the apparent S/N ratio. Caveat/physics: when you add a pre-amp, you'll get the amplified signal(s) PLUS the amplified 'background' noise PLUS the inherent noise of the pre-amp... Hence, as others have said, git yerself the best sweetest low-noise pre-amp you can.. In my area of work that typically involves $2-5k for a wee little box...

Resource #1 are the venerable HP/Agilent App. notes (I'm just not familiar with the relevant Rohde & Schwarz or Aniritsu tech notes, sorry!)::

http://cp.literature.agilent.com/litweb/pdf/5965-7009E.pdf (see hint 3!)

http://cp.literature.agilent.com/litweb/pdf/5952-8255E.pdf (p. 17)

http://cp.literature.agilent.com/litweb/pdf/5966-4008E.pdf - looks like a Bible, think I'm going to print this one and read it myself..this one will set you straight.

cheers

RF_guy