I don't see why its going to be a problem if you remove your amplifier, then normalize through your entire test set up, including any cables, attenuators, or whatever else there is.
Get the gain dead flat through the self calibrating normalization process.
Insert your amplifier... and there it is.
Your tracking generator when normalized should be more like +/- 0.1 db over any reasonable bandwidth.
That's the whole idea of it.
It very slowly sweeps and automatically corrects the output level, which generates some kind of gain correction lookup table which it then applies during normal use.
I suggest you study the operators manual for your particular spectrum analyser.
Something with +/- 3db normalized gain flatness is so unbelievably bad It must be faulty.
WOW really nice suggestion. I always thought the normalization proccess is purely done in software. You are actually saying that there is some kind of electronic correction involved in normalization. However, I've never seen amplitude accuracy after normalization specified in a datasheet. Better start to look for it.
There would be no point in doing it in software if the real RF levels are all over the place.
At least in my own spectrum analyser there is a variable gain stage in the tracking generator, as well as the switched gain attenuator right at the tracking generator output. The variable gain stage is driven from a DAC that is hooked up to a lookup table. So it slowly sweeps and carries out multiple gain corrections at a great many points over the entire bandwidth of the instrument. Its the only way it could possibly work from a few Khz through to several Ghz.
Its the tracking generator that is usually the problem, the wideband power amplifier can never be completely flat. The receiver front end part is just a mixer and should be (and is) much flatter.
Maybe other spectrum analysers work differently ?
Best to check the book of words, and see what it says.
So how do you get an external RF generator to track the spectrum analyser ?
While I have often used the tracking generator as a handy carrier source, with sweep width set to zero. I cannot really see any advantages of using an external synthesized RF generator, if you already have a built in tracking generator.
At least on my spectrum analyser I can get a dead straight horizontal line after normalisation. I know for a fact it has the variable gain amplifier in the tracking generator.
Thinking about it, there may also be some software fine tuning of gain as well, in addition to the analog amplitude levelling.
While the schematic tells the hardware side of things plainly enough, the software side is a bit more mysterious.
Its going to need to track fairly well, or you are going to slide down the sides of the bandpass filter and lose amplitude without any real way of knowing that is happening..
Just looking at the schematics in my service manual right now.
There is a block diagram of the tracking generator with an ALC input going to something they call a pin modulator.
This is carried out before mixing down to the final tracking generator output frequency, and before the tracking generator power amplifier and output switched attenuator.
That would make sense, because any harmonics created by clipping the amplitude would be eliminated in the low pass filter after the mixer.
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