I need a low cost VNA - Page 1
Forum section: electronics / rf-microwave

author: xzswq21
author_rank: Frequent Contributor
timestamp: October 08, 2019, 08:08:21 pm
content: HelloI want to buy a low cost VNA bcoz I'm working with filters. I have found some VNAs such as VNWA, TinyVNA,...which one is more reliable and better? I have to publish the results in IEEE.(my budget is $500~$600)Thanks

author: tautech
author_rank: Super Contributor
timestamp: October 08, 2019, 08:17:02 pm
content: Quote from: xzswq21 on October 08, 2019, 08:08:21 pmFrequency requirement ?

author: bob91343
author_rank: Super Contributor
timestamp: October 08, 2019, 08:39:51 pm
content: The great bargain is the nanoVNA. It is very low in price and does an amazing job. It has its limitations of course but for what they cost it's unbeatable.For operation at low frequencies there is a converter from China that shifts the 0 - 2 MHz input signal up to 10 - 12 MHz. I am tempted to buy one. The nanoVNA goes down to 50 kHz, low enough for many applications.

author: hendorog
author_rank: Super Contributor
timestamp: October 08, 2019, 09:23:14 pm
content: Some nanoVNA's are very poor at low frequencies. I have done a test here between the two different nanovna's I have:The second to bottom chart shows the differences at low freq.https://github.com/hendorog/nanovna_test/blob/master/NanoVNA%20comparison.ipynbThe white gecko branded one is much worse that the hugen supplied device. Hugen is this guy:https://github.com/hugen79/NanoVNA-HIn general the hugen nanovna was good under 300MHz which is in the fundamental range of the PLL. Above that they both get progressively worse, and whether that matters depends on your use case.Getting a good one isn't that easy. There are details about where to get them in hugen's github repo.Also, the cal kits in these nanovnas do not come with characterisation data. You will need that or else your error correction is just in the 'near enough' bracket.The bottom chart on this page shows this error when measuring a reference attenuator - the green trace is correct, and as measured by my cal kit supplier. The blue trace shows what a nanovna will display. The red trace is what I got from my 8753 when I removed the characterisation data from it - just as a double check.https://github.com/hendorog/nanovna_test/blob/master/NanoVNA%20test.ipynb

author: xzswq21
author_rank: Frequent Contributor
timestamp: October 08, 2019, 09:42:18 pm
content: Quote from: blueskull on October 08, 2019, 08:09:24 pmActually working with filters is a part of my project. for example I make 50MHz filter so I want to know the response (s11 and s21) and print it. then I use the filters in my real signal generator and sampling device. I have heard VNWA 3 is very accurate but I'm not sure.

author: TheSteve
author_rank: Unknown
timestamp: October 08, 2019, 10:02:19 pm
content: How much dynamic range do you require?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: October 09, 2019, 07:36:22 am
content: Quote from: blueskull on October 08, 2019, 08:09:24 pmI doubt any of the more high-ranking conferences will let you in if you show a measurement setup using such a VNA. (I don't want to get into the debate on if that is acceptable or not - just pointing out my experiences with reviewing conference papers myself).To the OP: If you want to publish with the IEEE, what is your background/field/reasoning? Do you work at a research group that is not well funded and thus doesn't have access to a 'real' (sorry for the term) VNA?

author: radiolistener
author_rank: Super Contributor
timestamp: October 09, 2019, 08:58:10 am
content: Quote from: hendorog on October 08, 2019, 09:23:14 pmyou're needs to update with more fresh firmware. Old version have instability issues. My NanoVNA works great at low frequency. The best dynamic range from 10 kHz to 300 MHz, about 70 dB for S11 and about 80-90 dB for S21.

author: xzswq21
author_rank: Frequent Contributor
timestamp: October 09, 2019, 09:25:57 am
content: Quote from: TheUnnamedNewbie on October 09, 2019, 07:36:22 amI want to measure the quality of my current source such as output impedance, SNR, passband and etc.I've seen some researchers built signal generator using DDS and FPGA (even with low cost DDS ICs and Rigol Oscop!) and used them in their research with the IEEE or IOP Science (master or PHD thesis). so I built a Signal generator and Sampling device with Avent's board and Analog devices components. I can show the results for them (HD2 and HD3 and SNR and etc)now I want to test the filters. when I build or montage a filter I should test it many times so I need a low cost VNA. the filters are used as Anti-aliasing filter. cut of frequency is 10MHz or 40MHz.

author: radiolistener
author_rank: Super Contributor
timestamp: October 09, 2019, 09:36:43 am
content: Quote from: xzswq21 on October 09, 2019, 09:25:57 amIf you're don't need more than 1 GHz, NanoVNA works good for such purposes. It cost 30-45 usd on aliexpress.Here is NanoVNA low frequency measurement for 24 kHz ultrasonic transducer:

author: tautech
author_rank: Super Contributor
timestamp: October 09, 2019, 09:47:55 am
content: Quote from: xzswq21 on October 09, 2019, 09:25:57 amDo you have a DSO and a sig gen that can sweep ?Learn how to do a Bode plot which can give you basic cutoff info.https://youtu.be/uMH2hGvqhlE

author: radiolistener
author_rank: Super Contributor
timestamp: October 09, 2019, 09:55:58 am
content: Here is my home-made BPF, tuned with NanoVNA for 145.3 MHz

author: radiolistener
author_rank: Super Contributor
timestamp: October 09, 2019, 10:22:38 am
content: It looks that my BPF works a little bad due to randomly untuned coil. A little tuning and now it's betterAmazingly, the price for device that allows to do that, is just 30-40 USD

author: MarkF
author_rank: Super Contributor
timestamp: October 09, 2019, 11:15:01 am
content: Beware.You may want to see this about the nanoVNA (starting @ 2:05):And discussion:https://www.eevblog.com/forum/chat/nanovna-shielded-ebay-sellers/Better choice (more expensive though):

author: radiolistener
author_rank: Super Contributor
timestamp: October 09, 2019, 12:21:11 pm
content: Quote from: MarkF on October 09, 2019, 11:15:01 amI already seen that. I think this is pretty normal behavior. In my opinion the root of cause for that is the common mode current on the outer braid of coax cable, because he uses unbalanced antenna with no RF choke.Different VNA have different ground, for example one has bigger metal case, another has smaller metal case. When you connect antenna to VNA with no RF choke, your VNA metal case will be a part of antenna. So, the antenna parameters will depends on metal case size and geometry.In order to avoid that, he needs to use RF choke. I think with RF choke on coax cable he will get the same results on both VNA

author: xrunner
author_rank: Super Contributor
timestamp: October 09, 2019, 12:35:31 pm
content: Quote from: radiolistener on October 09, 2019, 08:58:10 amIf you want that non-working red battery indicator to function you can install the missing diode on the board of the NanoVNA (D2 - SD103AWS-7 SCHOTTKY DIODE ).

author: radiolistener
author_rank: Super Contributor
timestamp: October 09, 2019, 01:42:04 pm
content: Quote from: xrunner on October 09, 2019, 12:35:31 pmThanks, I know that. I just don't have proper size SMD diode, needs to buy...Did you tested if this diode affects power consumption in power off mode?Currently my nanovna eat 50 uA in power off mode.

author: xrunner
author_rank: Super Contributor
timestamp: October 09, 2019, 03:31:51 pm
content: Quote from: radiolistener on October 09, 2019, 01:42:04 pmI will test it and report back here ...

author: hendorog
author_rank: Super Contributor
timestamp: October 09, 2019, 03:53:45 pm
content: Quote from: radiolistener on October 09, 2019, 08:58:10 amWill do, that test was on the shipped firmware IIRC. But you should state which nanovna you have, as there are hardware differences too.

author: hendorog
author_rank: Super Contributor
timestamp: October 09, 2019, 04:25:31 pm
content: Quote from: radiolistener on October 09, 2019, 08:58:10 amI updated the firmware to the latest edy555 on the google drive. It is still poor compared to my other nano below a few MHz (+/- 0.5 dB immediately after calibrating with port open) and is unusable below about 1MHz. Effective directivity is only about 25dB at 1 MHz - tested by leaving the load on after calibrating.I also tested with the latest hugen AA firmware, and it is the same.Possibly the decoupling caps are too small on this white gecko version I have. I got this very early, before many people were aware of them.There is a clear roll off at low frequencies.Which version do you have?

author: radiolistener
author_rank: Super Contributor
timestamp: October 09, 2019, 05:21:30 pm
content: Quote from: hendorog on October 09, 2019, 04:25:31 pmthat's strange, I have about -70 dB for S11 from 10 kHz.Below 10 kHz dynamic range drops down. At 2 kHz it's about 30-40 dB. But above 10 kHz it's ok.Quote from: hendorog on October 09, 2019, 04:25:31 pmI'm using hugen79 hardware with custom firmware based on edy555 code (some fixes to make measurements more stable and get sweep with unlimited points from PC)

author: xrunner
author_rank: Super Contributor
timestamp: October 09, 2019, 06:07:35 pm
content: Quote from: radiolistener on October 09, 2019, 01:42:04 pmIt's about the same - it fluctuates from 47 to 60 uA off.On, it runs at around 150 mA.

author: hendorog
author_rank: Super Contributor
timestamp: October 09, 2019, 06:19:06 pm
content: Quote from: radiolistener on October 09, 2019, 05:21:30 pmAha. Then it is not strange at all. The point of my tests was to compare my hugen hardware with my white gecko hardware.If you revisit the link in my original post (added again below) you will see a flat line in the middle of the chart - that is the hugen hardware. The wiggly blue line is the white gecko hardware. This test is with the port open and is from 10kHz to 6MHz.Second last chart on this linkhttps://github.com/hendorog/nanovna_test/blob/master/NanoVNA%20comparison.ipynbNot all nanovna's are the same. On groups.io there are some people who are affected by confirmation bias, and insist that their white geckos perform the same as the hugen unit. Not true.Is your stability fix is to improve the issue with wide spans and large step sizes that I identified in the joeqsmith thread?

author: xzswq21
author_rank: Frequent Contributor
timestamp: October 09, 2019, 08:35:47 pm
content: can I buy a second hand VNA on eBay?wish I had a setup that could generate a signal and capture the response!https://www.ebay.com/sch/i.html?_from=R40&_nkw=network%20analyser&_sacat=0&_udhi=700&_sop=16&rt=ncWhy NASA used a VNWA in their experiment?! watch @26m50s

author: virtualparticles
author_rank: Regular Contributor
timestamp: October 11, 2019, 05:17:57 pm
content: The ultra low-cost, "cheap" VNAs tend to be very drifty and of course there is no metrology to back up any claims of accuracy. Without accuracy it is difficult to make any claims at all about measurements that are made. I believe the best value on the market is the TR1300 from Copper Mountain Technologies. These are backed by an ISO17025 certified lab with traceability to NIST.https://coppermountaintech.com/vna/tr1300-1-2-port-1-3-ghz-analyzer/I don't usually do blatant marketing here but I believe I am answering the question.Thanks!Brian

author: xzswq21
author_rank: Frequent Contributor
timestamp: October 11, 2019, 06:10:36 pm
content: Quote from: virtualparticles on October 11, 2019, 05:17:57 pmyes it's good but I can't afford to buy it. I invented a current source in 2017 that could break the performance of all VCCSs (voltage controlled current source) in simulation and theory. I have invented a new topology.from 2017 I have been going to test this current source and my setup but nobody helped me. maybe this story makes you shocked but I'm still strong.now I want to buy a N2PK VNA. its dynamic range is 110dB and I think the performance is acceptable.https://www.eevblog.com/forum/rf-microwave/i-want-a-n2pk-vna/http://m0wwa.co.uk/pdf/VNA_comparisons.pdfa Chinese company helped me to receive the components of my modules and the current source, plus the PCBs were very good and low cost.

author: eb4fbz
author_rank: Regular Contributor
timestamp: October 11, 2019, 07:53:28 pm
content: Quote from: xzswq21 on October 09, 2019, 08:35:47 pmThey are used at CERN tooThe reason is there are few "pro" VNA working at <100kHz frequencies.

author: Bud
author_rank: Super Contributor
timestamp: October 11, 2019, 09:02:49 pm
content: Quote from: virtualparticles on October 11, 2019, 05:17:57 pmThe N2PK VNA was designed by a retired Bell Labs engineer. The VNWA was designed by a professor of mathematics at a German university. Both devices have proper error correction implemented, garanteed.Now, what are the credentials of the copper mountain designer?The only difference by big count is commercial production and availability of the copper mountain device. It maybe as drifty as the other two in terms of calibration stability, i do not know.

author: hagster
author_rank: Frequent Contributor
timestamp: October 11, 2019, 09:05:54 pm
content: CMT VNAs are excellent. Totally agree. If you can afford it, it beats the ultra cheap units hands down.I also can recommend the nanoVNA. It's surprisingly good. IMO it's better than the more expensive blue miniVNA.For 50MHz the nanoVNA works really well

author: E Kafeman
author_rank: Regular Contributor
timestamp: October 12, 2019, 11:12:50 am
content: QuoteAs amateur could question be, why donever evera qualified RF lab use one of these low cost VNA, costing maybe less then $1k instead of way more expensive VNA's?I can only talk for my lab. Reason is that it would harm productivity and job quality in a grade that I would not have any income to pay rent for the lab.Difference in cost for VNA is maybe a factor 50, and so would also my income differ.My lab is small but flexible, able to measure both active units such as cellphones as well embedded passive antennas. Can measure both in non echoic chamber and free space. All my instruments are connected to a PC which is fully controlling all of the instruments as well as a few other thing such as a 2D turntable and a reference antenna controlling unit (antenna selector and polarization switch).If working in a serious RF lab where instruments are supposed to communicate with each other in a simple way is a well developed standard instrument bus needed.IEEE 488/GPIB is what all professional instruments are using for communication. Instrument brands not even providing NI VISA driver is not attractive for any RF lab.Software and firmware of high quality and following standard rules is costly to develop and requires a lot of manhours. That makes it harder to sell such tools cheap.My VNA's, comtester, spectrum analyzers and even turntable are all connected to same GPIB bus. If my Copper Mountain VNA is away at calibration can it be replaced by my 20 years old HP8753 running same code at PC. Such flexibility is a must if you not can afford to buy two of each instrument, to have one as a backup and having software rewritten for each unique brand of instrument.A VNA that not have a fully implemented IEEE 488 structure is of no use for me due to increased cost, less flexibility and cost of time if software not is compatible between instruments.A standard job-flow when measuring radiation pattern of an active cellphone can be a turntable, that tells VNA when it have set its by PC ordered position so that VNA can perform a sweep and send sweep data to PC that after receiving this data switch reference antenna polarization, and then ordering VNA doing a new sweep and then ordering COM-tester to switch frequency and power level at the cellphone(DUT). Repeat this procedure 10000 times until all turntable position are measured.This procedure is not compareable with manual measuring VSWR with a single instrument where no extra software or interfacing is need besides basic measurements.Btw. using a VNA to measure VSWR is in a way overkill. It is a bit like using a oscilloscope just to measure a DC voltage. DC voltage can with higher precision be measured with a voltmeter.Same with VSWR. A Scalar Network Analyzer (SNA) is measuring VSWR just as good. Less complex and easier to measure with high precision.A VNA can measure two dimension complex impedance while a SNA only measure single dimension impedance vector lengths.It is a bit fun to read about all nanoVNA which all seems to be used to just measure VSWR.What i really like with my CMT VNA is that my measurement takes a lot shorter time due to faster response then many other VNA brands. A full sweep 201 point with better then 40dB directivity is typical done at 0.1-0.15 sec including transfer of data to PC, while my Agilent takes 0.3s for same sweep setup. Not much time difference but do probably save an hour each day if doing all day measurements, which increase my income corresponding amount.A VNWA can also measure at 0.3 s for 201 points but then with unknown IFBW and unknown effective directivity. For an professional instrument is it vital data to be able to say anything about measurement result.That should also be added as a typical difference, professional tools relative hobby tools, that its calibrated and guaranteed data is fully documented. Instrument with undocumented settings, these settings are not usable if measurements need to be traceable or be able to verify with a real VNA at any else measurement range.That is much an important tread in whole this business. By sharing reference antennas with other RF labs can my measurement ranges and its cables and instruments be compared with other similar locations. These antennas are often used as an extra check when range calibration have been done,checking with a known antenna that result is within expected tolerances and also after a measurement is done is a new check done with a reference antenna. Sometimes do it happen that a cable had become partly broken during measurement and that is then shown. Especially around turntable where a cable maybe is turned a bit each measurement and 1000'd times each day can such errors easy happen.That kind of error is important to find before any measurement report is written.The other thing I use VNA's for is live designing of embedded antennas and filters. My VNA is continuously measuring impedance, sends that data to PC where a software calculates needed adjustments including non ideal component losses and provide that data on PC screen and proposed corrections which is guiding me how to improve design.Here is a high repeated sweep speed needed with relative narrow bandwidth at each frequency point. Typical freq range is 500-2500 MHz.It is a big difference in "live feeling" when data update is done 10 times each second instead of just 3 times when cutting cu-tape at an antenna structure or trimming components.It is like driving a car and only getting short flashes from the road, 3 or 10 times pro second. 3 times pro second and only slow speed is possible.Some of the cheaper VNA's are a factor 100 slower, with unacceptable low performance and not able to easy use same software as the my other VNA's are using.My lab would be heavy degraded and with much less productivity with a bad tools and my measurements can not be certified with tools with unknown specifications.Most of my customers require that data is traceable, repeatable and done with calibrated tools.nanoVNA, yes I like it too. Excellent to play around with for anyone that not need a new VNA at cost $10k-100k.Many hobbyists seems to be using it just to check antenna VSWR and that is all they want to know.Some more curious and clever guys will try to better understand how to measure reactance with controlled phase reference, it is where a VNA is starting to be of any real use compared to a SNA. It literally opens a new dimension for antenna measurements filters and active circuits such as LNA and mixers, especially if of own design and in need for tune.A real VNA, it is a lot of money to buy one, so that is why I still also have a collection of older but cheaper HP8714-8753. They are still of good quality and in weekly use.My latest bought VNA is a CMT. What next VNA to buy, do I not know yet. What I know is that it will be compatible with my other tools and measurement system, easy to get calibrated (instrument parameters, calibration of measurement setup is something else) and if possible with instant, no delay sweep. Does not exist yet but it will maybe come.A VNWA is fun tool with hevy limtations in hard and software.Assuming it is in same range as a fully developed VNA usable at a RF lab with same functionality as a CMT/R&S/Agilent is not serious. In much, you get what you pay for.

author: xrunner
author_rank: Super Contributor
timestamp: October 12, 2019, 11:33:35 am
content: Quote from: E Kafeman on October 12, 2019, 11:12:50 amYou don't seem to understand something - it can be obtained for less than $50, sometimes less than even $30. It makes no difference if a ham or anyone else only wants to measure VSWR with it because ...it's less than $50 and can display the VSWR for all the resonant points for an HF fan dipole that works on 5 bands (see pic of my antenna) . There is nothing else in that price class as far as I know that can do that for a ham. So indeed even just for using it for VSWR, it's a GREAT instrument.

author: E Kafeman
author_rank: Regular Contributor
timestamp: October 12, 2019, 05:46:16 pm
content: Agree 100%.

author: bob91343
author_rank: Super Contributor
timestamp: October 12, 2019, 11:49:33 pm
content: The nanoVNA measures a whole lot more than SWR. It measures impedance resolved into R and X components, line length, individual components, attenuation, and many other parameters. I don't know how I ever got along before. This thing isn't just amazing; it answers a long time need. It's even a spectrum analyzer.Don't sell it short; it can replace big units costing thousands of dollars for many applications. I think every ham should have one. The usual antenna analyzers don't compare.Bob

author: OwO
author_rank: Super Contributor
timestamp: October 13, 2019, 04:41:13 am
content: Quote from: E Kafeman on October 12, 2019, 11:12:50 amYes but no. In practice antenna tuning is far easier when you have phase information as well. A resonance with little loss, for example, can NOT be seen on a SNA. There's also the issue that far higher spec hardware is required to achieve good directivity with a SNA because errorscan't be calibrated outand so the directivity of your bridge sets the upper bound of the directivity of your measurements. This sounds like not a big deal when you really only care that |S11| is < -20dB, but anyone who has used a SNA before will know that connecting just a cable will show visible ripples on the trace which may be hard to distinguish from a high Q resonance in the DUT, and this can't be removed with calibration. Commercial SNAs can hardly manage 30dB directivity while the NanoVNA with a home made cal kit (see hforsten cal kit) can easily reach 40dB directivity.TL;DR a cheap shitty VNA is superior to an expensive SNA even if you only care about SWR measurements.

author: radiolistener
author_rank: Super Contributor
timestamp: October 13, 2019, 05:28:19 am
content: Quote from: E Kafeman on October 12, 2019, 11:12:50 amNanoVNA is not Scalar Network Analyzer. NanoVNA is Vector Network Analyzer, this is why it has VNA in it's name.NanoVNA allows to measure not only VSWR, but S11, S21, magnitude/phase, R/X, Group delay and Phase delay. It also allows to do TDRIt covers almost all measurements that you needs from 10 kHz to 1 GHz. It allows to tune filters and antennas, check cables, LC circuits, etc. Yes it has limited dynamic range about 70-90 dB for 0.01-300 MHz and 30-40 dB for 300-1500 MHz range. But it is well enough for most tasks. And it cost just 30-50 USD.If you're needs some high technology aero-space and nuclear physics measurements with very high dynamic range and gigahertz range frequencies, you're needs some more expensive equipment. But if you're needs just to tune some filter or antenna, NanoVNA is a great choice

author: virtualparticles
author_rank: Regular Contributor
timestamp: October 13, 2019, 10:20:10 pm
content: CMT VNAs were designed by former aerospace engineers. We have a full time metrologist on staff and an ISO-17025 certified lab in Indianapolis which is able to test VNAs and provide a full record of uncertainties. I'm sure that the Nano implements some form of 12 term error correction. That's child's play and it isn't the point. The point is that there are no specifications for the Nano VNA whatsoever. No effective directivity, no effective forward tracking error, no effective reflection tracking error, no effective load match, no effective source match. Without these the measurements have no real accuracy and there is no way to estimate measurement uncertainty.That being said, the NanoVNA is an excellent tool for a hobbyist. It's the right price for amateur radio enthusiasts who want to make a quick measurement and don't need lab grade accuracy.

author: xzswq21
author_rank: Frequent Contributor
timestamp: October 13, 2019, 11:27:43 pm
content: Quote from: virtualparticles on October 13, 2019, 10:20:10 pmI want a second hand CMT VNA! but I couldn't find any used VNAs.

author: bob91343
author_rank: Super Contributor
timestamp: October 13, 2019, 11:33:50 pm
content: Yes it's an unfair comparison. However, so much functionality in such a small package at such a low cost makes this unit very attractive for most casual measurements. I own two old fashioned boat anchor VNAs and this little unit has taken over for most of what I do. Its limitations are not hidden, and can be worked around in many cases.The portability alone is a tremendous asset.I feel it's a major breakthrough; perhaps someone can improve on it so as to bring it closer to the big expensive units in performance. Even if not, I have made it my test equipment of choice for high frequency work.I am sure that many who produce the expensive units are wincing from the presence of this thing. And after all, great directivity and accuracy and dynamic range aren't needed much of the time.I gladly parted with the 'small change' needed to buy one and haven't regretted it.

author: Grandchuck
author_rank: Super Contributor
timestamp: October 13, 2019, 11:53:12 pm
content: The NanoVNA can't be beat for the money. Everything works and the software keeps improving. Its accuracy puts it beyond the toy category. Dynamic range is limited but the usefulness has far exceeded my expectations.

author: xrunner
author_rank: Super Contributor
timestamp: October 14, 2019, 12:04:55 am
content: Quote from: Grandchuck on October 13, 2019, 11:53:12 pmNow $19.99 shipped from US supplier!eBay auction: #333358656568

author: TK
author_rank: Super Contributor
timestamp: October 14, 2019, 12:11:59 am
content: Quote from: xrunner on October 14, 2019, 12:04:55 amIt must be a scam... all the items sold by this seller are around $20 and some of them look like the value is much much higher

author: virtualparticles
author_rank: Regular Contributor
timestamp: October 14, 2019, 05:13:19 pm
content: How are you assessing accuracy? Ah, the jpeg. It looks OK. Would be nice to see the actual difference at each frequency point, both phase and amplitude.

author: Grandchuck
author_rank: Super Contributor
timestamp: October 14, 2019, 05:47:22 pm
content: The instrument on the right represents a spectrum analyzer which can resolve magnitude relative to its own signal source, but cannot perform phase measurement. It is possible to use a hybrid coupler and multiple sweeps to obtain phase information, but that goes beyond my interests and needs.The main limitation (for my needs), as noted, is dynamic range. This is illustrated below. The dynamic range is down some at 200 MHz. This, of course, becomes worse at higher frequencies.

author: E Kafeman
author_rank: Regular Contributor
timestamp: October 14, 2019, 05:52:46 pm
content: Quote from: radiolistenerWe probably all guessed that.Quote from: radiolistenerVariations and subdata based on S11/S21. Just as known as what VNA stands for.It is nothing that affect nanoVNA limitations.Quote from: radiolistenerYour believing what is assumed to be uber-tech in your view is a bit childish. You must have better knowing then this.Maybe is you new at this VNA-thing. You think you know all functionality of a VNA after a week and have never ever seen any qualified use.No I will not perform nuclear experiments, just need a decent tool to be able to design your next wifi-router double band wide tuned internal antenna shape and its matching. That is one of the more common and simpler types of jobs I do.Have nothing against nanoVNA,it is fun and cheap and a good learning tooland some HAM may find it useful, but for my daily job, then is it a unusable piece of junk.It is fun to be toying around with a bicycle trailer, but do not ask a truck driver use a bicycle for long distance delivery ifyounot is prepared to pay for the increased cost and slower and smaller delivery.I am not a truck-driver, but problem is similar.I am now developing an antenna for a medical implant (something I am doing rather often).A bit tricky to create a high efficiency antenna due to big variations in dielectric and phase loss for such as blood relative fat but the high efficiency is important as it reduces battery replacement cost.Should I use a cheap VNA where important parameters must be excluded due to lack of VNA functionality when developing this antenna?It is possibly your or your relatives body I am designing for, not an aerospace nuclear thing.

author: OwO
author_rank: Super Contributor
timestamp: October 14, 2019, 06:38:10 pm
content: For antenna design I think you overstate the accuracy requirements for a VNA. In general as long as the hardware is reasonably linear, you have half decent calibration kits, and the calibration formulas used are correct (they are trivial so I don't see how you can implement it wrong), there aren't many sources of error in a VNA system. You can also VERY easily verify your setup by looking at, for example, a coaxial stub and checking that you see circles around the smith chart. For tuning antennas I find 1 sweep per second to be completely sufficient.Impedance measurement is a small part of antenna design; you only do it to sanity check that your resonance is at the right place and right Q. Much of antenna design knowledge is empirical and learned from experience ("seeing fields"). In your example of an implant it's an electrically small antenna so no matter what design you come up with it's going to be a magnetic dipole. You probably know the human body has high dielectric loss and no magnetic loss, so your antenna has to have mainly magnetic near field. There really aren't that many possible antenna designs here. As long as you set up currents flowing in a loop you're good. It's that simple.When I design antenna I spend maybe up to a few minutes on a VNA. For professional work I don't use the NanoVNA because I prefer slightly better dynamic range, but I certainly would not be using any of those high end VNAs or anything over $500 because low cost instruments get the job done just as well. Sure the low cost options on the market right now aren't that great, but it's only a matter of time before decent instrument hits the $200-500 range (that use something like the hforsten design).VISA/GPIB? Nah no thanks, I'd really rather use a C/C++ or even python API.

author: E Kafeman
author_rank: Regular Contributor
timestamp: October 15, 2019, 12:23:50 am
content: Quote from: OwOMy main experince is based on being working with antennas for some of the more well known cellphone brands.In that environment is you very alone with such ideas.When designing a multiband antenna at a small location do you need as big useable impedance space as possible that still is possible to tune to an efficiency goal.As antenna space often is fixed are available parameters antenna shape and reactive tuning.When I started to design embedded cellphone antennas 20 years ago was it a pretty much a new thing with embedded solutions and antenna shape was basically the only adjustable parameter with a very minor reactive adjustment possible.Typical was a piece CU-tape adjusted as well as possible for covering two bands, GSM900&GSM1800 or GSM850&GSM1900. Always PIFA back then.We tuned until we not was able to improve more, exported these S-parameters from VNA to diskette and imported it in software such as MWO in hope to improve bandedges with a tuning network.We did often fail as an already ok middleband would be detuned by any additional tuning of bandedges.Big advantage was when PC added a virtual matching network already during antenna shape design.A impedance curve which you not else could guess could show up as a perfect fit when combining a tuning network.It was a bit slow process but a big an improvement and timesaver. Instead of carrying a diskette was VNA data read by PC and directly imported to MWO.Antenna of typeDRAandIMDwas born due to the improved possibilities this did open.After a few years increased correct matching requirements as it not any longer was a 50 Ohm goal. TIS and TRP required improvement in PC software so that we could in an early stage predict if an antenna even had a chance to fulfill customer requirements and different impedance curves had to be weighted against each other.Then wanted cellphone makers to have more and more bands integrated at same antenna which increased need of bandwidth and still with good efficiency..PC software improved a bit further when it in realtime automatically selected best components and topology including its losses.Keeping track of correct impedance is then very important as well as selecting correct type of L/C component, size and type to get correct S-parameters.Anyone that ever have tried to implement a tuning network of say a T network with values based on VNA measurement in a cellphone, knows how easy it is to miscalculate due to improper impedance measurement.Even a smaller mistake and impedance curve will be more and more off for each additional component.This often a problem with several error sources. A typical problem is ground-losses, an assumed RF ground is not stable enough to handle decoupling current as an absolute ground. Ground becomes a bit soft, as an serial inductor of a few nH. Can be handled by a correct measurement model setup.Then due to this MIMO-stuff did antenna isolation become a new requirement and relative phase is then important as available antenna space is too small to create other then very minor difference in directivity and antennas are close to each other and sharing almost same ground currents.And now do you say that impedance measurement is a minor part of antenna design when you spend your 5 minutes at VNA.Are you really serious or are you a troll? You do honestly not seem to have any clue at all?Have you a slightest idea how much time that typical is spent at VNA when a typical 4G antenna for a cellphone is designed? Probably not.Do you spend any time to prepare a job in CST or HFSS?You have a big future in cellphone industry, you could learn us to save millions of dollar with your 5 minutes antennas.Not even Apple is as fast as you with its tools.They all worked hard a year to produce needed antenna for iphone4, no 5-minutes antennas.Quote from: OwO on October 14, 2019, 06:38:10 pmDo not believe that anybody will let you prove your point, which anyway seems to be unclear about what VISA and GPIB is.GPIB is a bus protocol, not a language, and VISA is a API standard available in several languages such as C#, VB.NET,LabView or python:https://pyvisa.readthedocs.io/en/latest/Using pyVISA or LabView to talk with instruments over a GPIB bus is no difference. Actual standard is updated several times. Latest code revision isIEC-60488-2which now is a common IEEE and IEC standard.Most now existing instruments must be able to communicate with its surrounding according to IEEE-488 or else do they have less functionality in a modern industry.Even my turntable is GPIB/VISA enabled. If I ever upgrades turntable will I then require it to talk same standard as I else must have a lot of software rewritten to non standard.Not only design labs, also many of the production lines of cellphones are controlled by using instrument buses such as GPIB. An old but still dominant standard. Many bigger solder-stations and pick&place machines as well as most instruments are talking GPIB and preferably using a terrible expensive bus-cable, to be able to handle production environment with high reliability. No wireless or USB allowed.At a higher abstraction level can you find SCADA, at least at the bigger production plants.Taking a simple example, in a production line have GPIB-enabled voltmeter failed. It can then be replaced with another GPIB voltmeter, independent of brand with minimal stop in production, and no need to replace software. As programmer is it important to understand how to not trash a standard. It is else very much possible to write GPIB communiction such that software only can talk with specific brand and model of VNA. A bit as building roads only fitting a special type of car.NI-VISA is probably now the biggest library of instrument drivers. No serious instrument is developed without providing such drivers, not even cheap oscilloscopes from Siglent ot Rigol.And your opinion is"VISA/GPIB? Nah no thanks", as clever guy do I handle TIS and TRP and advanced tuning in my had doing simple head calculations live once a second. 5 minutes and I am done. No need to think much about impedance anyway.Are you real or tries to be funny?QuoteAgain, you could save us a lot of money if you could learn us some of your tricks how to design implantable electronics.Current antenna situation:A pill camantenna. No loop. Very popular type of antenna in many implants.Another pill camantenna. Comparison of several antenna types. No loop.A pacemakerantenna. No loop.Another pacemakerantenna, No loop.A glucose meter implantantenna. No loop.Even if I try to remember older version of above, no I have not seen any loop.Have been some test to wireless recharge pacemakers with inductive coils. Above was a pacemaker antenna for 2.4 GHz but most brands of wireless pacemakers are using 900 MHz ISM-band.Have else hard to see where a loop can be used as implanted antenna except for antennas just under the skin such as biosensors of type 12MHz RFID andtear-sensorseven if just this senor antenna is a helix monopole shape feed by an loop and helix part which also is a part of the sensor.

author: xzswq21
author_rank: Frequent Contributor
timestamp: October 15, 2019, 12:54:37 pm
content: is there any second or third or fourth hand CMT VNA? the owner of N2PK doesn't reply my questions.

author: radiolistener
author_rank: Super Contributor
timestamp: October 15, 2019, 01:34:35 pm
content: Quote from: OwO on October 14, 2019, 06:38:10 pmpython is a .... badit's better to use C for firmware and C# for PC GUI.And I thing NanoVNA is good enough for antenna measurement. Of course if you don't needs to measure antenna at frequency > 1.5 GHz

author: mark03
author_rank: Frequent Contributor
timestamp: October 15, 2019, 02:31:33 pm
content: Quote from: radiolistener on October 15, 2019, 01:34:35 pmI don't think he was talking about the firmware (or the GUI) of the VNA itself, but rather how to interface with it. VISA is a monstrosity which is 10^X times larger than anyone can possibly justify (X >= 2). Python, by comparison, is a pure joy to use. Take a look at this:http://hforsten.com/trl-measurements-with-homemade-vna-and-open-source-software.htmland ask yourself how long it would take in C/C#, Labview, etc. to do the same analysis. I have an old GPIB-connected VNA but I am happy to be able to use it directly in Python with a vxi11 interface layer, without needing any of that VISA crud.

author: radiolistener
author_rank: Super Contributor
timestamp: October 15, 2019, 03:03:24 pm
content: Quote from: mark03 on October 15, 2019, 02:31:33 pmIt will take much less time in C/C#, but there is no SKRF library in C/C#. The only pros of python and con of C/C# is that python has SKRF library. That's it. Without SKRF, python has only cons.Just try to install python on windows xp and try to read SKRF code, you will understand why python is bad.

author: mark03
author_rank: Frequent Contributor
timestamp: October 15, 2019, 06:32:06 pm
content: Quote from: radiolistener on October 15, 2019, 03:03:24 pmThat is hard core. Well, clearly there is no accounting for taste(but why are you still using XP?)

author: hendorog
author_rank: Super Contributor
timestamp: October 15, 2019, 07:00:51 pm
content: Quote from: radiolistener on October 15, 2019, 03:03:24 pmBloody-mindedness over languages is a pointless exercise. There is nothing inherently wrong with python. It's just different, and has different strengths and weaknesses. Anything new takes time to learn.You are right about scikit-rf though. It has all of the VNA stuff you ever need built in. Writing a 'VNA' in python becomes a 5 minute job with only a few lines of code.I had never programmed in python before writing scikit-rf code, and have no particular attachment to it, but to me that is an absolutely massive advantage, and well worth taking.As an aside, there are people out there writing alternative VNA software for the nanovna, _in python_, who are not using scikit-rf. It takes them days/weeks to do what can be done in minutes. Reinventing the wheel is still a thing

author: virtualparticles
author_rank: Regular Contributor
timestamp: October 15, 2019, 08:32:11 pm
content: They tend to last a really long time and people won't give them up.

author: virtualparticles
author_rank: Regular Contributor
timestamp: October 15, 2019, 08:37:35 pm
content: I haven't seen any used CMT VNAs. There are occasional refurbished demo units available on the website from time to time though.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2019, 05:26:47 am
content: Quote from: hendorog on October 15, 2019, 07:00:51 pmthat's not pros of python. That's pros of scikit-rf library. The main con of scikit-rf is that it is written in python. If it were written in C or C#, it will be much more powerful and more transparent.I tried to port code from python and can say, python is very confusing language, it is not transparent and not intuitive. Often it hides logic and you may think that it works in such way, but it works in different way. That's the problem.The main issue with python is a lack of good code readability. You may think that python is easy. But that's not the case. Just try to port some complex python library code (for example scikit-rf) to another language and you will find a lot of pitfalls with python.Quote from: hendorog on October 15, 2019, 07:00:51 pmand this python-VNA will works incorrectly. That's the main problem of these "simple VNA/TDR in python" articles spreaded over internet. You can easily check this with matlab.The problem here is not with python itself. The problem here with a lack of understanding what is going on under the hood. But python make this problem more worse, due to a lack of code readability.

author: hendorog
author_rank: Super Contributor
timestamp: October 16, 2019, 05:52:23 am
content: Quote from: radiolistener on October 16, 2019, 05:26:47 amWell scikit-rf is only available in python. So it kinda is a pro of python in reality. I'm not convinced that changing the language would make it more awesome, but it's open source, so go for it.But I was not advocating python. I just found it wasn't that hard to pick up enough of it, such that I could use scikit-rf. I don't agree that it is super complex compared to anything else around. I have remembered though that I have used python a couple of times in the past.It is probably just that it is very different to what you are used to and so you have a learning curve. You think it works in a certain way based on what you know. Such is life in software. It keeps us humble.Also, IIRC from a while back, you were trying to understand the workings of the library. In my experience, delving into mature libraries is generally quite hard.Triply so when you don't know the language well. Better to start with just using the library and work your way from there.I mean even scientists and engineers are starting to use python, and they know nothing about programming. All they care about is getting a result. So it can't be that hard.All languages piss me off, so to me it is basically irrelevant

author: hendorog
author_rank: Super Contributor
timestamp: October 16, 2019, 06:01:15 am
content: Quote from: radiolistener on October 16, 2019, 05:26:47 amBollocks. I found a bug in the nanovna-saver C# application that nobody else had noticed, using a 5 minute python scikit-rf calibration test.The fact is, you can check it in many different ways. Nothing is bug free, but I think scikit-rf works pretty well.Have you found any bugs in it? Serious question, I haven't used it that much but haven't had any reason to fault it so far.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2019, 06:15:59 am
content: Quote from: hendorog on October 16, 2019, 05:52:23 amyes, I know that. Previously I learned different languages, such as C, C++, C+, Java, SQL, R, JS, etc... And this is why I said that python is confusing and not intuitive. It's my opinion.Quote from: hendorog on October 16, 2019, 05:52:23 amno, it depends on the language. I have experience with porting different math libraries from languages which I never heard before. And it's not so hard when a language is transparent and clean. This is not the case with python.Quote from: hendorog on October 16, 2019, 05:52:23 amThat's just marketing and hype. Many people use what marketing imposes on them. Nothing else. I already seen such things with javascript. This is just yet another hype temporary language for newbiesThe same thing happens with NanoVNA. I see there are a lot of hype about it. There is definitely some "big player" support for this hype. I don't know what is the reason. But this device is really cool, despite on it's limitationsBut again. Just try to install python environment on windows xp and you will have problems.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2019, 06:30:35 am
content: Quote from: hendorog on October 16, 2019, 06:01:15 amscikit-rf is really cool library for RF math. But this is just because it is written by people who knows all that math for RF very well. This is not because it is written in Python. If it were written in C it will be even more popular and more easy.

author: hendorog
author_rank: Super Contributor
timestamp: October 16, 2019, 06:37:01 am
content: Quote from: radiolistener on October 16, 2019, 06:30:35 amIf it was written in C it would suck at readability due to the lack of operator overloading to support complex arithmetic and the vector/matrix stuff.Check out the nanovna firmware. That is written in C and it is not pretty. Then compare that with scikit-rf, which has way more features, and you have a very clear winner.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2019, 07:46:31 am
content: Quote from: hendorog on October 16, 2019, 06:37:01 amC supports complex arithmetic, for example:Code:#include <stdio.h>#include <complex.h>void main(){complex float a = 3 + I*5;complex float b = 7 + I*11;complex float c = (a + b) / (a - b);printf("real: %f\n", creal(c));printf("imag: %f\n", cimag(c));}C language has very good code readability, because it uses math-based syntax.Quote from: hendorog on October 16, 2019, 06:37:01 amNanoVNA is written in C, but it doesn't use proper C language and really has code style problems. As example, for some unknown reason it doesn't use complex arithmetic in C (which can get better optimizations). But this is not related with C language, you can write in poor style with any language.The problem with C language is that it is very powerful and flexible. This is bad for novice, who don't know how to write proper and readable code. Because C allows to do something in different ways. This is language for professional programmers.If you want to learn object oriented programming, I can suggest C#. This is most beautiful and easy programming language with a bunch of all kind of modern language features. And it uses very clean and transparent C syntax.That's not a joke, and not marketing. If you don't think that C is easy and transparent, then it means that you're just don't know C language well

author: hendorog
author_rank: Super Contributor
timestamp: October 16, 2019, 08:21:27 am
content: Yes fair point. I was not aware that feature was in C nowadays, and presumably neither was nanovna author.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2019, 08:27:45 am
content: Quote from: hendorog on October 16, 2019, 08:21:27 amThat is not nowadays feature, it is old feature added in C99 standard. I don't think that 20 years old feature can be named "nowadays feature"

author: hendorog
author_rank: Super Contributor
timestamp: October 16, 2019, 08:40:48 am
content: Quote from: radiolistener on October 16, 2019, 08:27:45 amNow this is moving outside my knowledge of C compilers, which is not current in any way as you have shown. Many here are experts an I am not.But I do know that the compiler support lags the standard by a long long way. The compilers of 2000 would not have supported the standards of 1999.Not to mention that writing portable code used to be a goal when I was writing C code a long time ago. And that meant ignoring new features.Things have changed, but I haven't written much C at all for well over a decade.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2019, 08:48:29 am
content: Quote from: hendorog on October 16, 2019, 06:01:15 amdid you tried to install scikit-rf into STM32 firmware to use it in the NanoVNA?

author: hendorog
author_rank: Super Contributor
timestamp: October 16, 2019, 08:51:49 am
content: Quote from: radiolistener on October 16, 2019, 08:48:29 amNo, I am still waiting for you to change the STM32 code to support C99 complex number mathHowever, I did pull data from the nano and use scikit-rf with it on the PC. Worked great.Truth be told I am primarily interested in using the nanovna with a PC. Using that tiny UI is not something I can see myself doing very much.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2019, 08:55:57 am
content: Quote from: hendorog on October 16, 2019, 08:51:49 amnow try the same on PC with Window XP

author: hendorog
author_rank: Super Contributor
timestamp: October 16, 2019, 09:01:09 am
content: Quote from: radiolistener on October 16, 2019, 08:55:57 amWindows XP - from 2001?That's not far off 20 years old...

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2019, 09:05:22 am
content: Quote from: hendorog on October 16, 2019, 09:01:09 amBut it works faster than novadays widnows, it can works with 1-2 GB RAM and it don't requires internet connection and installing a bunch of gigabyte updates.For example NanoVNASharp works great under Windows XP with NanoVNA. Can you do the same with Python? Is it really so easy as you said before?

author: hendorog
author_rank: Super Contributor
timestamp: October 16, 2019, 09:19:09 am
content: Quote from: radiolistener on October 16, 2019, 09:05:22 amI have no idea. I dont have any XP boxes anymore. I have one rarely used window 7 box on a laptop which wont run win10 and i keep meaning to install linux on.But I think your general point is that C# will be compatible with more windows versions than python. That is reasonable. Microsofts single greatest achievement is their backward compatibility. It is outstanding and is better than any other OS AFAIK.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2019, 09:46:14 am
content: Quote from: hendorog on October 16, 2019, 09:19:09 amit won't work, I tried to run it on XP with no success.I got the following error at startup time on win xp:The latest Python also cannot be installed on Windows XP. The very old one can run, but it's libraries are not compatible with scikit-rf. So you cannot use scikit-rf either.I don't want to buy expensive notebook with tens gigabytes of RAM and buy internet connection for gigabyte updates just to communicate with VNAFor comparison, NanoVNASharp works great on an old notebook running windows xp with no need for gigabytes update through internetThat's the real life usage

author: hendorog
author_rank: Super Contributor
timestamp: October 16, 2019, 05:49:45 pm
content: Quote from: radiolistener on October 16, 2019, 09:46:14 amSuch is life in software. Version hell is painful. Old stuff gets discarded very quickly unless there is some commercial user who pays to keep it alive.Of course python is cross platform so you can easily avoid Windows 10 if it gives you heartburn. But that whole thing has been beaten to death everywhere, so lets not go there.

author: 5q5r
author_rank: Contributor
timestamp: October 17, 2019, 08:15:41 pm
content: Quote from: hendorog on October 16, 2019, 06:01:15 amWhich "nanovna-saver C# application": NanoVNA-Sharp, or NanoVNA-Saver (which is a Python application)?Did you report it? I don't remember seeing a bug report from you for NanoVNA-Saver, but I do get a lot of them.

author: hendorog
author_rank: Super Contributor
timestamp: October 17, 2019, 08:35:04 pm
content: Quote from: 5q5r on October 17, 2019, 08:15:41 pmNanoVNA-Sharp. I mentioned it on groups.io as I thought that Hugen developed that software as I downloaded it from the shared drive he made available.In reality, I don't know who developed that software, so no idea who to report it to.Quote

author: 5q5r
author_rank: Contributor
timestamp: October 17, 2019, 08:52:32 pm
content: Right, right. I just reacted to the "nanovna-saver" text, since that's what my application is calledAnd I'm doubtless the person you mentioned re-implementing functionality that's already in scikit-rf. Hello.I did look at scikit-rf, but there were a number of things I did not like about it, not least the fact that I didn't *understand* it. So part of writing this application was learning about RF mathematics.As is true for so many open source applications: I'm not writing it for the users, or to please them. I'm writing it for myself - because I enjoy it, and because I want to learn. If it makes others happy - that's an added bonus.As for Windows XP: I have no way to build applications for Windows XP, nor indeed to test them. It's been end of life for over 5 years. I'm amazed that there's any new software at all that will still run on it

author: hendorog
author_rank: Super Contributor
timestamp: October 17, 2019, 09:30:34 pm
content: Quote from: 5q5r on October 17, 2019, 08:52:32 pmAh copy that, yes sorry I got the names mixed upNo worries, I did the same myself, writing software, for much the same reasons a few years ago when I was building my own VNA stuff.Then HP stuff became a bit cheaper and easier to get to here, so I abandoned the effort. Now I just pull sweep data from whatever VNA into a PC, and turn to scikit-rf for the maths part.Based on what I know I would use scikit, but I've already been there done that with the RF calc stuff. Of course it's your software and your goals so you get to make the decisionsMaybe you will find some scikit-rf bugs with an alternative implementation