Rohde&Schwarz FSAS Spectrum and Network Analyzer - opinions

[GigaHurts]

Hey there, my first post on here.

I have bought an old R&S FSAS spectrum analyzer (804.9300.52) recently for my lab. I noticed that there is a suspicious lack of posts about this instrument in the forum. I am curious if anyone has any experience with this unit (note it is different from the R&S FSA spectrum analyzer in that it has a tracking generator. I assume the additional "S" stands for "source").

Especially this questions emerged in my mind:
1) Why call it network analyzer? Is it just cause it has a TG or does it actually have a reflectometer in the TG port to give scalar network analysis
I cannot find any documentation specifically for FSAS and the docs that I found (FSA model, operating manual and the service manual pdfs) do not mention the TG/network analysis aspect of its functionality.
2) Do you know anything about the history of this instrument? How does it stack up in terms of being developed as pro device or more for beginners? I read somewhere it was top of the line back in the day, and on paper it sure looks impressive. But again, there is a terrifying lack of info about this model on the internet (or maybe I am looking in the wrong places) especially coming to it from a bunch of HP/agilent/keysight instruments.
3) Any common faults? Any experience repairing this? What should I look out for during operation apart from the usual SA safety precautions?

I will appreciate any piece of info/factoid you might have on this! Thanks

[pdenisowski]

I just searched internally for information on the FSAS and came up empty - sorry   I believe it was manufactured in the 1980s, but that's pretty much all I know.

[DaJMasta]

I don't know specific details, but judging from a little info online and the front panel - it's a combination spectrum analyzer/scalar network analyzer with limited network analyzer functionality.  It probably has the single one directional RF input and relies on an external probe for the reference level.  The bandwidth seems pretty limited and the size/weight is massive, so my assumption would be that it was probably a pricey beast of limited use and it compromised network analyzer performance probably without a huge cost reduction.

I don't know if R&S made any devices in the 80s "for beginners", but at only 1.8GHz bandwidth and I suspect no integrated reflectometer, it seems pretty barebones for most applications.  As a result, the production run probably wasn't big and they probably got replaced with later, more capable units in the decade that followed it's release.

Speculation, so take it with a grain of salt, and it's probably functional enough as a spectrum analyzer - but I think the actual capability of the network analyzer portion is probably pretty limited, especially without external equipment, so I'd treat it as an SA with a TG.

A little blurb from a 1992 R&S brochure

For
example, there are spectrum analyzers that display
the amplitude of a test signal as a function of
frequency over a wide frequency range in nearly
realtime on a CRT (eg Spectrum Analyzer FSA from
Rohde & Schwarz). There are also network
analyzers which have a tracking generator as well
as the frequency-selective analyzer (eg Scalar Spec-
trum and Network Analyzer FSAS).

Previous FSA troubleshooting post: https://www.eevblog.com/forum/repair/rs-fsa-issues-with-level-glitches-of-2nd-lo/

From some datasheet info I've seen out there, the TG maxes out at -5 dBm, though it probably has an inline mechanical attenuator since it can go down to -100 dBm

This person seems to have access to a manual (mentions it's in German) https://groups.io/g/Rohde-and-Schwarz/topic/fsad_and_fsas_differences/75726831

[videobruce]

How much do these weigh? 30 or 40lbs apiece??
Then there is the power consumption; what 100, 150 or more watts each??

No thanks. 

[GigaHurts]

Its something like 60 kg. Better not check the consumption

[GigaHurts]

I just searched internally for information on the FSAS and came up empty - sorry   I believe it was manufactured in the 1980s, but that's pretty much all I know.

Thanks, it seems R&S wipe their servers periodically . Though I was able to download an FSB and FSC operations manuals from R&S website, but as you say, I couldn't find any (public) mention of FSA or FSAS.

Honestly, this where R&S kind of drop the ball compared to keysight - they have publically available manuals, service info, even CLIPS for equipment from the agilent and HP days but this might be by design to avoid the deluge of hobbyists like me contacting them with questions

[GigaHurts]

I don't know specific details, but judging from a little info online and the front panel - it's a combination spectrum analyzer/scalar network analyzer with limited network analyzer functionality.  It probably has the single one directional RF input and relies on an external probe for the reference level.  The bandwidth seems pretty limited and the size/weight is massive, so my assumption would be that it was probably a pricey beast of limited use and it compromised network analyzer performance probably without a huge cost reduction.

I don't know if R&S made any devices in the 80s "for beginners", but at only 1.8GHz bandwidth and I suspect no integrated reflectometer, it seems pretty barebones for most applications.  As a result, the production run probably wasn't big and they probably got replaced with later, more capable units in the decade that followed it's release.

Speculation, so take it with a grain of salt, and it's probably functional enough as a spectrum analyzer - but I think the actual capability of the network analyzer portion is probably pretty limited, especially without external equipment, so I'd treat it as an SA with a TG.

A little blurb from a 1992 R&S brochure

For
example, there are spectrum analyzers that display
the amplitude of a test signal as a function of
frequency over a wide frequency range in nearly
realtime on a CRT (eg Spectrum Analyzer FSA from
Rohde & Schwarz). There are also network
analyzers which have a tracking generator as well
as the frequency-selective analyzer (eg Scalar Spec-
trum and Network Analyzer FSAS).

Previous FSA troubleshooting post: https://www.eevblog.com/forum/repair/rs-fsa-issues-with-level-glitches-of-2nd-lo/

From some datasheet info I've seen out there, the TG maxes out at -5 dBm, though it probably has an inline mechanical attenuator since it can go down to -100 dBm

This person seems to have access to a manual (mentions it's in German) https://groups.io/g/Rohde-and-Schwarz/topic/fsad_and_fsas_differences/75726831

Thank you for your reply, you inspired me to look through that groups io page and I did in the end find the supplementary manual for the network analyzer function! If anyone else needs it, it is at the following path https://groups.io/g/Rohde-and-Schwarz/files/FSA and free subscription is necessary to view the files.

I haven't read it yet, but a quick view reveals it has some reflection measurements (was not super important for me, I was going to use a coupler for the S11 measurements, but having it is a nice bonus).

Thanks again for pointing me in the right direction!