Does VNA > SA ? - Page 1
Forum section: electronics / rf-microwave

author: Finderbinder
author_rank: Regular Contributor
timestamp: January 23, 2024, 03:10:37 pm
content: These are different equipment but have some common capabilities too. SA usually needs an additional tracking generator. VNA seems is more "integrated" device.So, may I assume VNA have more capabilities than SA in general? Does VNA covers SA capabilities and in addition have its own advantages?How many % of SA capabilities cover branded VNA?Sorry if questions are stupid but I had no chance to play with any of these

author: selcuk
author_rank: Frequent Contributor
timestamp: January 23, 2024, 03:17:25 pm
content: They are very similar with respect to their building blocks. But if you have two of them, you probably never use one instead of the other. They are very different in use cases. So normally you don't consider that VNA is a more capable SA.

author: ejeffrey
author_rank: Super Contributor
timestamp: January 23, 2024, 04:03:50 pm
content: A VNA is more capable than a SA with a tracking generator used as an network analyzer. For this reason tracking generators are relatively uncommon now except on low end instruments. Modern SAs aren't even simple swept receivers anyway so they aren't really natural fits for a tracking generator.But a spectrum analyzer is still quite useful for is normal job, and not really interchangable with a VNA. Which one is more important depends on what you do most.

author: Bud
author_rank: Super Contributor
timestamp: January 23, 2024, 04:35:48 pm
content: You cant assume that at all, and none of VNAs include SA function, except maybe for some software defined models where both functions are implemented in software separately, but not as a result of one particular architecture. Apples and oranges are both fruits and both are round, but they taste differently.

author: Finderbinder
author_rank: Regular Contributor
timestamp: January 23, 2024, 04:44:19 pm
content: So, if I want to explore signals/waves as it is I should use SA. If I want to deal with antenna, or other hardware tuning, parameterization I should choose VNA. Otherwise I will get little to no benefits. Right?

author: RAPo
author_rank: Super Contributor
timestamp: January 23, 2024, 04:54:43 pm
content: Yes, but you can buy a SA that also has VNA capability.

author: p.larner
author_rank: Frequent Contributor
timestamp: January 23, 2024, 05:21:59 pm
content: this seems like trying to compair apples to oranges to me.

author: tautech
author_rank: Super Contributor
timestamp: January 25, 2024, 03:06:00 am
content: You can mimic some VNA capability with a SA with TG port and a reflection bridge however the quality of the bridge plays a big part in the results.I went down this path a few years ago when I got my first analyzer and puckered everytime I used it for fear of damaging it.Now on my 4th, a 4 port VNA with SA capability, none of the previous damaged in any way and 2 now gone to other homes.However a somewhat cheaper SVA1032X is still my all time fav, a single port VNA/SA combo with TG.TG (Port 1) doubles as a tracking gen and VNA reflection (S11) port with the RF In port for SA work or VNA Through (S21) measurements.A press of the Mode button lets you switch between SA and VNA.A couple of threads using them:https://www.eevblog.com/forum/rf-microwave/antenna-project-log/https://www.eevblog.com/forum/rf-microwave/what-really-is-this-antenna/

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: January 25, 2024, 01:24:22 pm
content: Quote from: Finderbinder on January 23, 2024, 04:44:19 pmIf you want to dabble without spending a fortune on high end test equipment, the "Tiny" instruments are really good. Only buy from official sources as there are a lot of fakes around. I have a TinySA Ultra, a TinyPFA and a NanoVNA H4.The TinySA includes a signal generator, but it doesn't function as a tracking generator.https://tinysa.org/wiki/https://nanovna.com/The NanoVNA H4 can also be loaded with phase frequency analyser firmware to operate as a TinyPFA without needing to buy separate hardware, it can be easily re-loaded with VNA firmware too.https://www.tinydevices.org/wiki/pmwiki.php?n=TinyPFA.HomepageA lot of instrument for little cost and which fit in your desk drawer. The above pages include details of where to buy.SJ

author: chilternview
author_rank: Frequent Contributor
timestamp: January 25, 2024, 01:30:11 pm
content: There are a few rare instruments that combine VNA and SA functionality. The HP 4396B for example, which also has the ability to analyse DUT LCR etc. vs frequency. It's limited by its 1.8GHz maximum frequency (its sibling the 4395A is even more limited to 500MHz, but will work down to audio range).

author: RAPo
author_rank: Super Contributor
timestamp: January 25, 2024, 01:36:49 pm
content: A very interesting video on the topic of tinysa and tracking generator is here:https://youtu.be/X4dGaC0QiEw?si=tdjht5K2iLw-2i2T

author: Finderbinder
author_rank: Regular Contributor
timestamp: January 25, 2024, 06:01:11 pm
content: I had thoughts of buying tinySA Ultra + LiteVNA 64. But if I pay only a small part of the branded “real” equipment (albeit old), then I think I will also get only part of the capabilitiesRight?

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: January 25, 2024, 06:13:53 pm
content: Quote from: Finderbinder on January 25, 2024, 06:01:11 pmMore importantly, do you have a use for them? The Tiny instruments are a little fiddly to use (a small touch screen and a “jog” wheel), but given their low cost and specification, you can forgive the user interface.See attached for a NanoVNA H4 sweep of a 1296 MHz antenna and a TinyPFA plot comparing a home made GPSDO (red trace) with a commercial Leo Bodnar GPSDO (green trace), the reference was a rubidium frequency standard. The additional Windows software is free.Surprising what you can measure for modest cost.SJ

author: switchabl
author_rank: Frequent Contributor
timestamp: January 25, 2024, 09:12:50 pm
content: Quote from: Bud on January 23, 2024, 04:35:48 pmPretty much all the top-shelf VNAs from the big brands have spectrum analysis options these days. I realize the OP is probably not in the market for a PNA-X but I'd expect this to become more common in the future, it's all digital IF anyway (I think I actually saw a lower-end R&S VNA with SA option a while ago; EDIT: probably a ZNL).At the other end of the spectrum (pun intended), there's entry-level SAs like the R&S FPC that come with a basic T/R VNA option. Hand-held instruments (like the FieldFox) also frequently do both.Of course there are performance trade-offs (and you usually don't get full image rejection on a VNA) but being able to completely characterize a mixer or amplifier in a single setup is pretty neat.

author: Finderbinder
author_rank: Regular Contributor
timestamp: January 25, 2024, 10:23:55 pm
content: Quote from: switchabl on January 25, 2024, 09:12:50 pmYesssssssages to wait till prices drops to affordable

author: Teledog
author_rank: Regular Contributor
timestamp: January 28, 2024, 07:27:04 am
content: Have the Nano VNA V2. It's OK..I use it mostly for antenna tuning.Have an ancient (900Mhz) analog SA with a sweep/tracking generator (SM5011).I like to use both for a sanity checkFor tuning antennae(?) with a SA with a tracking gen .. at least at sub-Ghz, you'll need a directional coupler ie:https://www.minicircuits.com/pdfs/ZFDC-10-21.pdfEyeballing the 6Ghz Ali unit with the tracking gen ..https://www.aliexpress.com/item/1005005854680743.html

author: pdenisowski
author_rank: Super Contributor
timestamp: January 28, 2024, 10:15:29 pm
content: Quote from: switchabl on January 25, 2024, 09:12:50 pmYes, the ZNL has a spectrum analysis option. And yes, some of our handhelds can be used as either a spec an and/or as a VNA

author: rfdave#gmail.com
author_rank: Contributor
timestamp: January 29, 2024, 01:32:10 am
content: They're different tools. Think Screwdriver and wrench. Both useful tools, but they're different.

author: MarkT
author_rank: Frequent Contributor
timestamp: February 04, 2024, 10:34:00 pm
content: For a high end SA you are looking for frequency resolution and accuracy, wide dynamic range (low noise). For a VNA its more about reproducible calibration and precision connectors and cables so that you have good impedance resolution and stability. Combine all those and you have an instrument that can do both well, and also be effective at emptying your wallet!Simplisitcally, SA + TG + directional coupler = VNA.A VNA with 10kHz minimum RBW is more useful than a SA with a minimum 10kHz RBW, A <=10Hz RBW is great to have in an SA, pretty much superfluous in a VNA.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: February 07, 2024, 05:33:20 pm
content: Nah, frequency accuracy/resolution/rbw isn't the limiting factor these days, here's the problem:* SA wants filters* VNA doesn't need filters* Filters are unstable, reflective, absorptive, and expensiveBoth get filters: YIG filters are wildly unstable by VNA standards and mashing together a traditional YIG-based SA with reflectometers to achieve VNA capability would end in disaster. Just imagine transplanting the multi-dB amplitude accuracy spec from a YIG SA to a VNA. Yikes! High-IF architecture and filter banks make this much less of a problem, taking it from "disaster" to "tradeoff," but it's still there.Neither get filters: Ok, the VNA doesn't want filters and doesn't need filters, what about the SA? Can it live without them? Sure, but now you have a ZIF SA with image rejection so bad that the phantom signals take up 80% of your graticule or SIS that makes wideband signals look like bathtubs at completely the wrong levels and hides intermittent signals. Not great.-------------------Life is tradeoffs. What are the options?Separate SA and VNA: Best of both worlds, but you pay for it in money, space, weight, and convenience.One port gets filters and the rest don't: This is the compromise that most combined SA/VNA units seem to strike. The ports aren't identical anymore, but if you need SA you use the SA port and for VNA you often have a situation where one reflection is less important and you can stick that on the SA port and live with the slightly degraded performance. It's pretty ok, all things considered.No ports get filters: You see this on high-end VNAs because it is assumed that any engineer using one is a big boy/girl and understands how ZIF/SIS works and what the resulting "Spectrum Analyzer" can and can't do.

author: tautech
author_rank: Super Contributor
timestamp: February 07, 2024, 06:51:20 pm
content: Throw the SNA5000A models into the mix, specifically they are a VNA (2 or 4 port) but also offer a SA option assignable to any port.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: February 07, 2024, 08:19:01 pm
content: Speaking of which, what's the architecture on those? High-IF? Software image suppression?

author: Bud
author_rank: Super Contributor
timestamp: February 07, 2024, 09:16:10 pm
content: Quote from: tautech on February 07, 2024, 06:51:20 pmThst would still just be a multi-tool with some of the hardware shared between the tools and the rest of processing done in software.