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Re: nanoVNA for Nerds
I bought my NanoVNA in large part to have a solution looking for a problem to solve. My main use for this device was the SWR sweep capability for my antennas, but I soon discovered previously unknown problems that now needed a VNA solution. How pleasantly convenient.
Having a real time Smith Chart display is absolutely invaluable for getting a good feel on impedance for one. More, I have some SDR receivers that can be overloaded by a 50KW AM broadcast station a few miles away. The solution was to build custom filters. My first one, using an online passive filter design tool, was a 500 KHz LPF. It's quite satisfying whipping up a design and then see it perform. I found that even using 10% tolerance parts and tiny axial inductors, I could still produce an effective filter. The VNA proved to me that specifying a cutoff frequency with a good gap to the required cutoff frequency meant I could get by without strict tolerances and hi-Q torroid inductors. My latest filter design was for a 22nd order 3.5 - 30 MHz BPF. I never would have ever tried that without my NanoVNA. And it works, knocking down the BCB and giving an excellent, although not as deep [nor needed], upper cutoff. This exercise was just as much about learning how to build and test the filter as its actual use. Testing 455 KHz IF filters made for another fun experience, especially since I had to compensate for the wildly different 2K Ohm I/O impedances. Yes the NanoVNA for me was a solution looking for a problem to solve. Kinda like going to school and learning how to solve a problem and then look for a problem to solve, lab exercises so to speak, but with immediate real world applications. Chicken or egg? Which comes first is not important. Just pick one and work towards the other. |
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Re: nanoVNA for Nerds
Theory is always incomplete. It is said that the field of thermodynamics learned much more from the operations of steam locomotives than steam locomotives learned from thermodynamics. Often electrical building codes lag advances in electrical technology by decades. In my specialty of ship hull inspection there are always the ship design drawings and the "As Built" drawings. "We ran out of 10# plate so we used 12# plate until we could get more from the foundry."
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Correction of error introduce by a transmission line connect to the VNA port 1
Hello everyone,
I am a beginner in using the NanoVNA, I have a calibration problem after connecting a transmission line into the VNA. You can see some pictures of the result in the attached document after connecting the cable to the VNA in the attached file. Could someone tell me how to correct the impedance shift introduced by the cable? Thanks I went to the "electrical delay" menu to correct the problem by adding a delay but it got worse. I don't know what to do. I want to solder the cable afterwards into a PCB where we have antenna traces. |
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Re: Common ground and 2-port measuring
Hello Ed,
Op vr 15 jul. 2022 om 11:23 schreef Ed G8FAX <ed@...>: Hi Victor,Thanks, but when I get a better grip on the OCFD (aka being ableto model and include in that moe the Choke) I plan to revisit teh webpage(as it is now somewhat cluttered with all kidn of experiments I did. I think all are valid but it coudl be better structured with the present knowledge I have;-) I must confess, I have only read parts of it. What springs to my mind, isI did not look at power issues (I think I will using my equipmentin the QRP range), but I agree it could be extended with that. Who knows, when I have the need. Also, have you considered an open wire feed rather than coaxial? AgainI did not do that (yet?). Also here I am planning to use coax and thus I restricted intially to that. When we are discussing models, the OC model comprises of a CM part and DM The 'equivalent' circuit maps the best my measurmenets is the model of Guanella (to ideal transformers; a transmission line to represent the DM and a ractance+resistance to represent the CM); see also Owen Duffy's page: I am relatively new to the nanoVNA (I have H4.2) and still exploring the very many menu options of firmware 1.2.00. It appears that the instrumentI use NanoVNA Saver for that (or the s1p/s2p files and my excel spreadsheet). In respect of the G3TXQ link, I agree, it is not clear. What I do get from reading it is that his chokes are coils made from coax cable wound on a I think this is part of the dsicussion of terminology;-) 1:1 Guanella (which I use and also G2TXQ) is lso a 1:1 transformer, but I call it a Choke as I use it mainly as a choking device. I also think there is a terminology issue with calling this ¡®common mode¡¯,Teh 1:1 Guanella Choke (whihc is also used by G2TXQ on that page (indeed coax on a toroid), can be used in the CM0 (crocs on both end of braid plus shield) or the CO (crocs on both end of braid or crocs on both end of shield) onfiguration (he is certainly not used CM2 or CM3 configuration) The HAL article is nice and also this one: I think the OC, DM and CM are nicely explained and modelled. But IMHO this article and HAL's are abouvt power-supply chokes (a lot of windings), whcih are build a little different than RF chokes (more aligned with transmission line). All the best, Victor P.S. just received the toroids, need to test the complex mu so I can design these 'ideal' Transfomers for the DM measurement. |
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Re: nanoVNA for Nerds
¡°In theory there is no difference between theory and practice, while in practice there is ¡°
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Benjamin Brewster On 15 Jul 2022, at 08:35, F1AMM <18471@...> wrote: |
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Re: Common ground and 2-port measuring
Hi Victor,
Oh wow, what a fantastic webpage you have, full of useful information. Your attention to detail, investigations and experiments is exemplary and I congratulate you for all your efforts. I must confess, I have only read parts of it. What springs to my mind, is the choice of ferrite material and power handling, this will alter any model if capabilities are exceeded. I¡¯m sure you are aware of that and if not addressed this already, will do so. Also, have you considered an open wire feed rather than coaxial? Again forgive me if you have already looked at this alternative. When we are discussing models, the OC model comprises of a CM part and DM part. The CM parts has parallel resistances and reactances. I¡¯m sure you are aware that these can be also be represented by equivalent series circuits. Thus by translating the shunt inductors with the resistors, the circuit could be re-drawn with a form similar to that of a transmission line (TL). By the way I would call that configuration a ¡°balanced Pi¡± arrangement. Anyone following this discussion, not familiar with converting parallel to series circuits, I refer in the first instance to I am relatively new to the nanoVNA (I have H4.2) and still exploring the very many menu options of firmware 1.2.00. It appears that the instrument now has capability of presenting results in either series or shunt form, I have yet to investigate this, and many more things. This might help when producing values for a model. In respect of the G3TXQ link, I agree, it is not clear. What I do get from reading it is that his chokes are coils made from coax cable wound on a toroid and wonder as it is not a transformer arrangement if it is applicable/relevant to our current discussion? I also think there is a terminology issue with calling this ¡®common mode¡¯, a point you raise on your lovely webpage, to me I see it more as a ground loop between inner and out of coax line. Thoughts? Considering his test arrangement and firmly bonding grounds of generator and measuring ports, I wonder/think he connects croc clips to each end of the braid, as that is where the ¡®choking¡¯ is required, else what what be measured on the inner route and centre? I am not familiar with the ¡®open¡¯ measurement technique, to be honest, never heard of it until you raised it in a previous post, so can not give any helpful comments on how useful it is for determining CM & DM performance of a CMC. I will study the ¡®HAL¡¯ link information and get back to you. Like you, I have also been wondering about suitable baluns (transformers), if there are any reasonably priced commercial items available or how to make one, so very interested in what core you use, number of turns and wire gauge. I think some experimentation is required and happy to give it a go, but my schedule means in August or later. I was also wondering if a suitable CMC wired or used in voltage mode would be a suitable item as a transformer here, thoughts? Kind regards Ed, G8FAX |
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Re: nanoVNA for Nerds
F1AMM
I have always been a practical and experimenting man, sometimes, defying theoryIf the "practice" is not in agreement with the "theory" it is that there is an error (a fault) in one or the other, to see in both. -- F1AMM Fran?ois -----Message d'origine-----De la part de Observer vendredi 15 juillet 2022 09:22 |
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Re: Common ground and 2-port measuring
Hi Francois,
Thank you for your contribution. The image you refer to gives a method for testing aspects of a 4;1 voltage balun, see link in the other ref you provided Here we are discussing measuring certain parameters of a CMC, so not directly applicable. If the CMC was placed between the two baluns' then the arrangement would allow some tests to be made on its performance. The effects of the two baluns would need to be compensated for. Kind regards Ed, G8FAX |
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Re: Common ground and 2-port measuring
Hello Ed,
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I mostly do CM0 measurements on Chokes, but I checked the OC one to see what it did. I think G3TXQ used OC, but not 100% sure (he does not fully describe his setup in: . OC and CM measurements are close (except for power-supply chokes the OC shows an additional resonance freq. which does not really emerge when I do the OC on RF chokes) <by the way, the webpage of 'unknown author' is me> The OC is T4 (Fig 3e) in this article: It also gives the equivalent circuit for it: ig. 9a Just to be sure, my main point is looking at Miro's question: how to do DM measurements. I have not really done Dm measurements (as I was interested in CM values of my Chokes), I think most people do DM measurements without the two additional transformers (to go from unbalanced VNA post to balanced ports to connect the DUT, Fig 16b). Which is related to Miro's question. So I want to see what the difference is between these two DM measurements with and without the Transformers. I ordered these cores for these transformers a month ago, I hope to receive them soon. I also don't have any winding advice. If someone has this, I am interested. All the best, Vicctor Op do 14 jul. 2022 om 18:44 schreef Ed G8FAX <ed@...>:
Hi Victor, |
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Re: nanoVNA for Nerds
On Thu, Jul 14, 2022 at 06:10 AM, Don Rolph wrote:
Be careful about suggesting using nanoVNA as an SWR Meter. Most SWR Meters are used between a transmitter and an antenna to show the SWR in the transmission line at an operating frequency. The nanoVNA is connected to a transmission line and antenna to show what the SWR will be when fed from a transmitter at various frequencies. It would lead to disaster if someone connected a nanoVNA between a transmitter and antenna. But we knew what you meant. |
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Re: Should I upgrade firmware, and if so which version to use?
I believe this should be a personal decision and not the consensus of a
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group of...... Do the research on your own, present your conclusions to a group, and make a decision. Don't reverse the first two steps. Just my opinion. Dave - W?LEV On Thu, Jul 14, 2022 at 10:16 PM Dave Fugleberg <dave.w0zf@...> wrote:
After 35 years in IT, I¡¯ve learned a few things about software/firmware-- *Dave - W?LEV* *Just Let Darwin Work* --
Dave - W?LEV |
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Re: Should I upgrade firmware, and if so which version to use?
After 35 years in IT, I¡¯ve learned a few things about software/firmware
upgrades. The decision to update *anything *depends on 3 factors: business need, supportability, and risk. This is true of your NanoVNA, your PC, your radio, or whatever... Only YOU can determine if YOUR 'business need' requires an update- examples would be desired functionality or usability enhancements, or fixes to bugs that affect your use of the system. 'Supportability' factors include whether support from the provider is needed or desired, and what their policies are. Don't expect much help on a very old version of software that's had a lot of development since that version was released. If you ask a software provider for help, they will likely (and rightly) ask you to update to the latest before trying to troubleshoot your issue. They're not being difficult - they just don't want to spend time on something that may already be addressed in a newer version. 'Risk' is the factor that's often overlooked or misunderstood. There are many kinds of risks. For a standalone device with embedded firmware, the security risk is pretty low, but there can still be operational risk (not fit for purpose, etc). That's where 'if it ain't broke...' makes sense. For a device that's going to talk to a hostile network (which these days means most any network), the risk of vulnerabilities in old software increases exponentially. In that case, updates are important whether business need or supportability suggest a need for an update or not. In ham radio, some of the latest transceivers with ethernet connectivity come to mind. I would want some assurance that the manufacturers are keeping up with security patches, and apply those in a timely manner. Don't forget to include the risk to others in your risk assessment - unpatched devices on the internet are routinely used by the bad guys to attack or defraud others. Don't be that guy. In summary, the question of when or whether to update any software or firmware is neither 'apply every update' nor 'never update' - it has to consider business need, supportability, and risk. You probably do that without explicitly thinking in those terms anyhow, but deliberately thinking through it will either confirm or challenge your instinctive decision. 73 de W0ZF On Wed, Jul 13, 2022 at 4:20 AM David Wilcox K8WPE via groups.io <Djwilcox01@...> wrote: Somehow you all missed my point a few days ago¡.. much of the upgrades in |
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Re: Common ground and 2-port measuring
Hi Victor,
Thank you, I await your results on DM measurement after your parts arrive, if you are kind enough to post them. I hope you have better experience than I on delivery, I ordered some items from China just after Christmas, they arrived last week! What else do you see as needed with my DM method to obtain a complete model for DM measurement? Our discussion started out as, is there a difference, significant or otherwise between your DM measurement technique and my simpler approach to practical measurement. It has widened now. Re models and your footnote link - This is part of a very long and detailed webpage of an unknown authors investigation and experimentations ¡°to determine which Hybrid Choke/Transformer to use for a 40m OCFD¡±. As of today, no conclusion is yet written. The section you bring to my attention today appears to relate to the ¡®OC¡¯ measurement and model rather than DM/CM representations. I do not see any comparisons between OC and DM/CM i.e. how well does OC compare to DM/CM, do you have any information on this? Kind regards Ed |
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Re: Should I upgrade firmware, and if so which version to use?
I also upgrade.. In some cases just minutes after an upgrade is available (example sdrradio console)... But that's off topic grin
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I am also a member of test team group.. So if you are not fear of upgrading and maybe step backwards if there is a bug (or just wait for next release) then i try to be right on the last version.. Be it with sdrc.. Or with v2plus4 or v2 That helps developers to find bugs easier Imagine you find a bug.. And tell programmer that it is "somewhere in the last 20 versions"... Not easy to find If you have only one device.. And need it regularly.. Then maybe stay a bit slower on upgrades... But i have three different v2 units.. So i test a new fw in one.. And if ok i upgrade the other two Cause those are a bit different. Its a good test... I have a v2 modded with a 4 inch screen... An saa2n modded to v2plus (means 4 inch and n socket) And a v2plus4 (4 inch but much different fw cause bootloader used is closed source) So three slightly different units. If i have some sparetime i will add sd card to one... And use fw from dislord that supports storage on card.. So.. The v2 and all of its clones, brothers and daughters... Is a living project Where one can stay on a unit and fw and just use like it is.. Or upgrade and modify (sometimes with solder work)... And have all newest bings and boings (sd card storage, real time clock, battery display) So its your choice to have an up to date unit.. Or stay in an earlier fw Dg9bfc sigi Am 14.07.2022 16:45 schrieb "David J Taylor via groups.io" <david-taylor@...>:
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Re: nanoVNA for Nerds
You will find a lot of useful videos on youtube... If you looked a few of them you at least know some basics
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What is that damned smith for?? How to calibrate What are all those traces mean How to measure this or that ... So i highly recommend to watch a few of those.. Greetz sigi dg9bfc Am 14.07.2022 16:44 schrieb "Chuck, KF0CT" <chu_r@...>:
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Douglas Butler
Ken
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