the demodulation function is a joke
Furthermore, you even cannot store any decoded data stream into a file for post analysis.
It is more for playing around with HAM communication and looking at GSM/2G modulation.
you probably confuse the modulation analysis function with modulation decoding (demodulation).
In SSA you have modulation analysis and this feature has nothing to do with decoding. It is used for something else - for example, you can set up the RF amplifier so that it does not introduce nonlinear distortions affecting the modulations, etc.
For example, I suggest watching this video in which such an example of digital modulation analysis is discussed - and watching how the distorted RF amplifier behaves.
"TSP #159 - Siglent SVA1032X 3.2GHz Spectrum & Vector Network Analyzer Review, Teardown & Experiments" - The Signal Path (from the time of 44:20)
https://youtu.be/ToVJTKCyIU8?t=2660In general, I recommend this channel on YT, you can learn a lot of interesting things about measurements and learn about the equipment - in a pleasant form (without having to go into the literature - I know that reading books is a problem for many today)
The defined "ready-made modulations" (GSM/2G etc.) are only a help, so that you do not have to do it manually by setting.
If you want to analyze some faster modulations, you should choose RealTime spectrum analyzer (for example SSA3032X-R). Alternatively, you can buy professional equipment (e.g. some communication analyzer from R&S). What you expect is a specialized communication analyzer, not a universal spectrum analyzer (where such options are only often a limited addition).
If you want to analyze TV, you can use devices such as the R&S ETL TV analyzer or the compact R&S ETC TV analyzer.
https://www.rohde-schwarz.com/pl/products/test-i-pomiaru/analizatory-transmycji/rs-etl-tv-analyzer_63493-9255.htmlhttps://www.rohde-schwarz.com/pl/products/test-i-pomiaru/analizatory-transmycji/rs-etc-compact-tv-analyzer_63493-12060.htmlThere are also specialized analyzers to work in GSM/UMTS/ LTE networks. Unfortunately, it is not the case that when you buy one of the cheaper universal spectrum analyzers on the market, you get the possibilities of specialized communication analyzers. It's a bit like after buying a Victorinox pocket knife you complain that you can't unscrew the wheel on a truck with it.
So I suggest that you first read a little bit about analyzers, their uses, etc, before you start determining what's wrong and what's right. Unfortunately, the lack of knowledge later causes such disappointments.
I also do not recommend using the factory mode. This mode does not guarantee that the spectrum analyzer is fully operational. It is known that there are some bugs with VNA. However, no one knows 100% if similar problems occur in other functions of the spectrum analyzer. Especially that now the publicly available method allows you to expand the capabilities of the device - without having to turn on the factory mode.