[KB9RLW] wanted to build a vector network analyzer (VNA), but then realized he could buy a ready-made one without nearly the cost it would have been only a few years ago. The network in this case, by the way, is an electrical network, not a computer network. You can use a VNA to characterize components, circuits, antennas, and even feed lines at different frequencies. The miniVNA Pro is economical and can exercise circuits from 1 MHz to 3 GHz. You can see the review in the video below.
There are a few ways to actually create a VNA, but in concept, it is a sweep generator, a detector, and a means to plot the response at each frequency in the sweep. So you’d expect, for example, a resonant frequency to show a peak at resonance and a band reject filter to show a low point.
One of the things interesting about the device is that it uses Java software. That means it doesn’t care much what platform you want to use. The software can show two different plots at once, so [Kevin] hooks it to his 20 meter antenna and shows how it can plot the SWR and impedance around the frequency of interest.
The instrument can be USB powered with the same cable you use to connect the PC. However, it also has an internal rechargeable battery. That battery charges on USB and can operate the device with Bluetooth. We can imagine that being handy when you want to climb up a tower and connect it directly to an antenna as long as you stay in Bluetooth range of the PC. There’s also a phone app, so you can go that route, if you prefer and [Kevin] shows the device working with Android. Of course, you could probably rig a Raspberry Pi on your belt and then use WiFi to let someone on the ground remote desktop in to run measurements. A lot of possibilities.
If you want to roll your own, that’s possible, of course. If you want to get by a bit cheaper, there are less expensive options.
http://miniradiosolutions.com/pro-vs-tiny/
The “pro” model described here only goes up to 200 mhz. NOT 3 ghz as claimed here. The “tiny” model is the 3 ghz unit
Actually, it goes to 200MHz. Big difference.
Pedant
I own the original MiniVNA version and it goes up to 180MHz. One drawback of that older version is that it cannot detect the phase sign so all the Smith charts are horizontally reflected.
A much cheaper option (135$) which I also use with good results is the NWT4000 (138MHz to 4.4GHz). You can find the NWT4000 on chinese sites like aliexpress. A copy of the documentation is in this page: http://uglyduck.ath.cx/reviews/archive/2016/03/NWT4000_Network_Analyzer.html
HRO website: https://www.hamradio.com/detail.cfm?pid=H0-012128
Ali Express: https://www.aliexpress.com/item/200M-miniVNA-PRO-Vector-Network-Analyzer-Frequency-0-1-200-M-RF-Antenna-Analyzer-VNA-Signal/32719799486.html?src=google&albslr=221698338&isdl=y&aff_short_key=UneMJZVf&source=%7Bifdyn:dyn%7D%7Bifpla:pla%7D%7Bifdbm:DBM&albch=DID%7D&src=google&albch=shopping&acnt=494-037-6276&isdl=y&albcp=756822904&albag=35305934810&slnk=&trgt=61865531738&plac=&crea=en32719799486&netw=g&device=c&mtctp=&aff_platform=google&gclid=Cj0KCQjwz7rXBRD9ARIsABfBl80abSX68IyONV2GDJVKWPK-4nQk2f50TsVdqCstnZFuxnMRrepDvawaAjTFEALw_wcB&gclsrc=aw.ds
Interesting Alan: The miniVNA PRO on AliExpress from your link is $320 vs. $490 at HRO from the mRS exclusive distributor in the U.S. WOW! What’s up with that? Is the AliExpress thing a Chinese Clone/Fake?
Probably cost-cut version and magical Chinese free shipping…
Also – exclusive distributor = monopoly, thus don’t expect competitive pricing
Sigh, the lowest frequency is to high for anything i want to do at home (need to go down to DC for system characterization for control loops). The highest frequency is too low for most things I need to do at work.
Have you seen the CircuitGear CGR-201? 1Hz to around 1MHz in VNA mode, and a lot cheaper than the miniVNA. Seems like it would be handy for control loops, but I’ve only used it for filter analysis.
http://www.syscompdesign.com/CGR-201_ep_62-1.html
I’ve got a CGR-101, it’s been with me for a long time. I’ve gotten a bunch of higher bandwidth equipment since then but it’s still handy sometimes.
Over at HGR surplus they have been selling some old HP VNA’s that start out at 10hz.
You could use the Digilent analog discovery 2 for 5MHz and below. I’m just making an adapter add-on for doing network analysis easily. Uses the same principles but at lower frequencies. Check it out. Might be what you need.
See also: the $500 PocketVNA. It has a significantly larger frequency range (500 kHz to 4 GHz) plus solid linux (and Win/Mac) support with it’s Qt based application. I’m using mine a ton to test/tune antenna and filters. Examples,
Antenna measurements, http://superkuh.com/conical-spiral-antenna.html , http://erewhon.superkuh.com/vivaldi-tapered-slot-antenna-and-figures.jpg , http://erewhon.superkuh.com/Zinc-Prototype-K-antenna-TEM-Horn-S11-Smith-Plots.jpg
Filter measurement: http://superkuh.com/dgs-bandpass-filter.html
I tried all the rtlsdr, hackrf, and other bodged together with directional coupler scalar network analyzers but the real problem with those is calibration. Calibration is hard and without it you just get bonk results. The PocketVNA makes calibration a very simple and intuitive process.
Er, I linked to the wrong filter page. I haven’t received the SMA edge connectors to test the defected ground structure filter linked above. This is the correct link to my fully built and PocketVNA tested dual-coupled combline bandstop filter, http://superkuh.com/radio-filter-simulations.html or directly to the result, http://superkuh.com/radio-filter-simulations.html#hardware
That is a really interesting blog!
What kind of calibration options are available for these things? Cal kits for the network analyzers I work with are usually $5k and up. Granted, this is for equipment that goes up to K-band and beyond. But if I still have to shell out that much for cal standards, kinda defeats the purpose of spending so little on the analyzer itself. I could probably fabricate open / short / load standards, but they’d be narrow-band, and I’d need access to a better NWA to characterize them before defining the cal kit.
Thru-reflect-line calibration is great, and much more forgiving of imperfect cal standards, but it’s only applicable to 2+ port analyzers…
Probably the priciest item in such a cal standard set would be the “sliding load”. (Not to mention just a 50 ohm load with SWR < 1.05). But I doubt these tiny units go to the effort of calculating the imaginary locus of a perfect 50 ohm load like the commercial VNAs do.
The rough equivolent of these units would have taken a 6RU footprint back in the 80s….
Maybe, maybe not. There weren’t really any low-end VNAs at the time.
The VNAs from the ’80s were certainly behemoths, but they still radically outperform these offerings. Consider the 8753B, a mid-range product: 100 dB of dynamic range, source power variable from -5 to +20 dBm with continuous sweep from 300k-6GHz, input crosstalk better than 100 dB, dynamic accuracy of +/- 0.05 dB and 0.5 deg over a 50 dB input range, etc. Most of these devices spec none of these things, let alone approach those specs.
Nice plastic shielded gear, with impressive high precision BNC reference plane :- )
One of the best “quality/price” ratio is, imho, the DG8SAQ “VNWA”, with an impressive documentation and a top quality (closed source) user interface. Far more evolved compared with the different software available for the mini-VNA.
But, in the Ham world, the best VNA ever with the most impressive precision and dynamic is definitely the N2PK (which could be used with many softwares, including the one made by DG8SAQ).
A little bit more complex is the “Scotty’s modular spectrum analyzer” which is a VNA also, and covers all frequencies from .1 to 3000 MHz.
I’ve used all of these instruments and kept the vnwa, the MSA and N2PK… and sold asap the mini-vna.
marc