Setting up a lab, SA, SNA, VNA...

[MacIntoshCZ]

Hello, I am trying to get equipment for the laboratory. I would like to know what everything (circuit parameters) can be measured by individual devices such as an oscilloscope, spectrum analyzer, scalar analyzer, vector analyzer, etc... At the moment I have experience with an oscilloscope, so I probably wouldn't discuss it. The spectrum analyzer itself, in layman's terms, measures the signal level across the frequency spectrum. When I have a TG, I can also measure the frequency response of the filters (gain only). Is the scalar analyzer actually just a spectrum analyzer with TG? Can anything else be measured with it? The vector analyzer measures scattering parameters. Unlike the scalar analyzer, it also measures phases? My personal focus is more on power electronics, I'm also interested in wireless transmission, so I'm probably dabbling in RF as well... I'd like to hear your recommendation on what kind of equipment actually makes sense to get, for example, it seems pointless to me at the moment to own a spectrum analyzer with TG and at the same time scalar analyzer. On the other hand, I read again that the scalar analyzer is more accurate than the spectrometer with TG and at the same time it is much cheaper (but I saw that it is a problem to find a functional detector) So I really don't know where to turn =D. I'd appreciate advice from people in the field, I'm just learning. Alternatively, what specific models of (used) devices would you recommend.

[MacIntoshCZ]

I think having VNA would be nice, but i would like to have one with frequency range starting at few Hz to say Ghz? I have found HP 8751A but many comes without test set on ebay =/ and test set frequency starting at 300Khz. Why ? =/

[Bicurico]

Unless you explain the scope of the lab you are trying to set up, it will be difficult to give you answers.

The main question is: What is your budget? And how would you like to make a profit from your lab?

If you spend 200.000€ on a VNA from Keysight or R&S - how long would it take to pay off the investment?

Is it a hobby lab? Then you are limited to a Siglent SSA2021-P, cross-converted to a Siglent SVA1032.

Is it for a school lab? Then you need to decide between one professional expensive that will absorb all your funds or many (1 per student in class) low-cost device (i.e. TinySA Ultra + NanoVNA). I would say the second option is better, because EVERYONE would get hands-on training, as opposed to only be allowed to look at this ridiculous expensive device, that is too expensive for a student to break by accident.

Is it for a start-up? Perhaps take a look on how expensive it is to subcontract i.e. EMC testing.

Is it for R&D? What kind of products do you want to develop? How much money is to be earned? Again, I doubt that SA/VNA will pay off, because a startup would typically use a modular approach using already certified components and rely more on the software side. But then, who am I to know...

Final recommendation: Never ever ask in a tech forum, what test equipment to purchase, without stating the exact needs. It is like asking in a car forum: What car should I buy?

Cheers,
Vitor

[RogerThat]

By the sound of it, you are probably starting in the wrong end(buying the equipment before knowing what to do with it). The equipment you list are specialised instruments and I wouldn't recommend just buying to equip a lab. When you NEED it, then buy it and at that point you will also know what specs to look for etc beacuse you know what you want to do with it. 

[MacIntoshCZ]

You are right, with this discussion I would like to clarify in my head which devices I need and which ones I don't. I currently own a tektronix 492 spectrum analyzer, which I have used several times to measure the signal from antennas. I want to ask, is it possible to use a noise generator and a swept oscillator instead of TG to measure the characteristic (gain) of the filter? The noise generator should work, but the swept oscillator HP 8350B must somehow synchronize with the LO of the analyzer. So I wonder if it is better to buy a scalar analyzer or a swept oscillator. We are talking about used devices from Ebay, I am poor for new ones =D

[RogerThat]

just for info, be careful with cheap ebay noise generators and signal generators, they might damage your SA input.

If you don't have a tracking generator you can just set the sweep on the signal generator to something 2-3x higher than the sweep from the SA. Put the SA in peak hold, take a quick coffee and when you come back you have the result. If you have access to a good noise generator that would work also.

[tggzzz]

I currently own a tektronix 492 spectrum analyzer, which I have used several times to measure the signal from antennas. I want to ask, is it possible to use a noise generator and a swept oscillator instead of TG to measure the characteristic (gain) of the filter?

Yes, with limitations, principally:

• all the power from the noise source hits the SA's inputs. Need to be careful not to overload the SA's delicate and expensive mixer
• the SA "ignores" almost all the received power, which limits the overall dynamic range
• where there is non-linearity[1] there will be intermodulation products, again limiting the dynamic range but also introducing spurious responses

https://entertaininghacks.wordpress.com/2015/08/10/measuring-rf-filters-with-a-homebrew-1-5ghz-scalar-network-analyser-costing-3248/

With a splitter-combiner or similar RF component, it is also possible to measure the reflection parameters.

We are talking about used devices from Ebay, I am poor for new ones =D

If you are thinking about RF, you will become poor. If you don't believe that, look at the cost of new cables and connectors and loads/shorts from reputable manufacturers/suppliers!

Think about what a vector-voltmeter might be able to achieve. At the very least that will make you think about the tradeoff between your time and your cash!

[1] i.e. everywhere, to some degree

[MacIntoshCZ]

So do you think having scalar analyzer for instance Hewlett Packard 8757 is better than trying to achive this with SA and sweeper? What i have seen those SNA is cheap to obtain but detectors are rare to find. What is purpose of detectors?

edit:
Oh, i though SNA has sweep generator built in, but having look at datasheet it requires external signal =/

[tautech]

FWIW here's my take based on SA experience over the last few years.

My first was a SSA3032X and when SVA1015X was released got one of those too mainly for antenna work.
Soon after when SVA1032X were released got one of them which the currently is my fav due to its capability and feature set.

The list of accessories needed can be daunting however with just a few basics you can get the rest when/if you need them.
FYI an antenna project from a few years back.
https://www.eevblog.com/forum/rf-microwave/antenna-project-log/

Since then I also had SNA5004A, a magnificent instrument however well beyond the more simple needs I have so it went to a customer as SSA3032X and SVA1015X have done.

Should you need know about anything in these product lines just ask.

[MacIntoshCZ]

Do you think is possible to score HP 8753ES 6Ghz (or other variant with s test set?) around 1000USD? Since i am from CZ i am limited also with shipping cost that could be  500-1000 USD, also i need to add to whole sum 21% tax...
Does price of this equipment year by year or its maintaining its value?

[LukeW]

just for info, be careful with cheap ebay noise generators and signal generators, they might damage your SA input.

If you're working with expensive instruments like a SA or VNA, it's important to know (a) the maximum specified power input to the instrument's port and (b) the maximum possible power output from the device under test, and use the right attenuators if you need to.

If you don't know the power from the DUT, you need to start with strong attenuators and measure carefully, or use another instrument like a Bird RF power meter or similar. Or, measure the DC power input to the DUT with a 50R dummy load on the RF output, and from there infer the maximum possible RF power into 50R.

[MacIntoshCZ]

Thanks for info 👍

[MacIntoshCZ]

I was just aiming at one 8753ES 30khz - 6Ghz with inverted display issue hopping that it will be just bad connector. Auction started at 1k$ + 400$shipping. I aimed at 1,5k max without shipping and someone at last seconds just bid another 850$  :'(. So it ended at 2350$. I was out of game whole time...

[Bicurico]

Sorry to ask, but why do you want to buy such a machine? What do you want to measure with it?

Do you have any idea how prone to failure such an old machine is? Will you be able to repair it? Where are you going to source the components for it?

Just to get an idea: I own 3 (!) HP 8694E and only one is working. I was, up to now, not able to repair the other two. And meanwhile I purchased two PSU's for them, because I have three broken ones, which I was not able to repair, either.

Consider how much time you need to spend to be able to repair them, IF you have access to discontinued components!

Also, don't assume it is "just" an issue with the display and a bad connector. Nobody owning such a device will sell it cheap because of a broken connector. Anyone can repair that. You might get out-of-spec calibration, broken mixer, broken input stage, etc.

Do yourself a favour: determine what equipment you really need and go from there. If you want to buy second hand equipment, then your goal is not to setup a lab, but to restore broken device for self-satisfaction or profit.

And if you really want a SA and/or VNA, the best option is to buy a SSA3021X-Plus and cross-comvert it to a SVA1032. You will be able to measure up to 3.2GHz. Not suitable? Then the question is once again: what is your applictaion and/or requirement for the lab and will you make a profit?

Regards,
Vitor

PS: You remind me of myself - I often make up a need just because I fell in love with some random equipment I don't really need...

[MacIntoshCZ]

Mostly i am interest in component measurement with smith chart up to 6Ghz (since my dad is into drones), so impedance matching i guess?. S21 parameter could be also handy i think. I am hobbyst but there is seek for doing electronics as job one day, therefore i want full potential VNA =D.
That siglent looks good, can it measure everytginh 8753es can? Just freqeuncy range could be higher =/.
"PS: You remind me of myself - I often make up a need just because I fell in love with some random equipment I don't really need..." 100% yes =)

EDIT:
That siglent can not measure S22 or S12 parameters?