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Re: Measuring ferrite beads
#test-jig
Hi Urrich
I think it is worth mentioning that only when a toroid/clamp is measured in a closed chamber the true charcteristics of the material is measured. Using an open air loop you are "fooling yourself" as field lined are escaping. This statement might get someone to protest, as they have so and so good experience but fact is fact. We got Fair Rite to admit it was not the true characteristics for the material they published, but that was the best they could do (at that time) using a short wire thru a test core. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af UlrichKraft Sendt: 20. oktober 2019 15:25 Til: [email protected] Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig Hello Kurt, that is a wonderful description of what you three did a while go when measuring the performance of ferrite materials. Very cool stuff and because I'm just looking in exactly that topic I have a few questions questions to your fixture. I'm still on a "beginner level" using VNA for measuring ferrite impedances, so sorry for any stupid questiosn. When you have inserted the ferrite bead and turning the adjustment knob it will contact the SMA F connector at some point. What type of SMA connector did you use? I would imagin that the inner conductor gets damaged pretty fast after using the fixture a few times? Or is that a "special" type of SMA with more robust inner-conductor design ? Do you know if something similar is commercially available? Secondly, I like to characterize the ferrits with DC-BIAS current from 0 up to 10 Amps.. That changes ferrite impedance and frequency, depending on saturation of the material. See For relatively large ferrite cores it might be easy just adding an additional wire through the inner dimeter, with a DC-current. That way the RF- and DC wires are separated. But for smaller components like wound-beads (e.g. Fair-Rite 2961666671) I need to "inject" the DC current into the signal line of the VNA. Do you have any experience how to do that best? What kind of RF-filtering / DC-blocking needs to be build ? How is calibration performed then? The additional filtering will definitely change the overall S11 response, but I want to see only the ferrite effect on the Impedance and not any effect of that filter. The intended frequency range is up to 500 MHz for #61 material, but ideally for full span of nanovna up to 1 GHz. |
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Re: Measuring ferrite beads
#test-jig
Hi Ulrich
First of all I give you the link to another document not published but in small "circles" and it will interest you I am sure to the Test Chamber and Measurements above 500MHz.pdf It might be entered in the browser directly as the io groups messages does no like my notation ? Regarding the adaptor, to which the male centerpin is engaging, is a straight forward threaded SMA female female adaptor with a hex nut on either side of the top plate, with a toothed washer on the top side. For the male centerpin to find the female center bushing I just press inserted a small 2mm long section of the Teflon part for a male SMA adaptor. It has a hole of 1 mm and that is enough guidance for the male pin to home in on the female bushing. I insert an image of both sides, and in my case it was a bulkhead adaptor used but it does not matter what you use. No wear to consider. Just for the fun of it I show you my mico-chamber Regarding the DC biasing I have no experience, but I do not see a big problem in that either. The center pin resistance is very low so not much DC blocking required to protect the VNWA TX out. The biggest problem is to know the impedance of the RF isolation between the DC supply and the center pin to be high enough. I imagine a SMA T adaptor and some sort of resistive or inductive impedance to block the low impedance of the DC supply. The impedance of the T adaptor seen from the RF isolation is removed by the calibration on the output side of the T-adaptor connected to the test chamber (with no DC current applied). So the impedance for determining the inductance of the internal ground rod without the toroid and with toroid is straight forward measurement as such. How many Amps the SMA adaptors can carry is a matter for studying. In my last mail I said some nonsense about the spreadsheet, which is used for determining the rod impedance and that only. How to subtract the inductance for the measurement with toroid is a matter of some mathematics I think is covered by already available material else revert to the matter Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af UlrichKraft Sendt: 20. oktober 2019 15:25 Til: [email protected] Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig Hello Kurt, that is a wonderful description of what you three did a while go when measuring the performance of ferrite materials. Very cool stuff and because I'm just looking in exactly that topic I have a few questions questions to your fixture. I'm still on a "beginner level" using VNA for measuring ferrite impedances, so sorry for any stupid questiosn. When you have inserted the ferrite bead and turning the adjustment knob it will contact the SMA F connector at some point. What type of SMA connector did you use? I would imagin that the inner conductor gets damaged pretty fast after using the fixture a few times? Or is that a "special" type of SMA with more robust inner-conductor design ? Do you know if something similar is commercially available? Secondly, I like to characterize the ferrits with DC-BIAS current from 0 up to 10 Amps.. That changes ferrite impedance and frequency, depending on saturation of the material. See For relatively large ferrite cores it might be easy just adding an additional wire through the inner dimeter, with a DC-current. That way the RF- and DC wires are separated. But for smaller components like wound-beads (e.g. Fair-Rite 2961666671) I need to "inject" the DC current into the signal line of the VNA. Do you have any experience how to do that best? What kind of RF-filtering / DC-blocking needs to be build ? How is calibration performed then? The additional filtering will definitely change the overall S11 response, but I want to see only the ferrite effect on the Impedance and not any effect of that filter. The intended frequency range is up to 500 MHz for #61 material, but ideally for full span of nanovna up to 1 GHz. |
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Re: errors of "error" models
#63 : @Dr. David Kirkby from Kirkby Microwave Ltd
/g/nanovna-users/message/5324 20 October 2019 Hello, Thank you very much for your kind invitation. In fact, you violate open doors, because it was in our intentions from the beginning to build a short PDF on this part of our most successful research here. But, due to our duty of responding first to all these questions regarding our work, this have to be delayed a little - if you don't mind of course. Anyway, allow us, please, to have our strong reservations if the contents of this PDF shall finally cover the taste of all honorable members of this group. After all that said, allow us, please, to present our work in the way and sequence we have to know better than any other else and -most of all- without any further defamation of it. In the Name of Scientific Knowledge at last. Sincerely, gin&pez@arg 63# |
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Re: errors of "error" models
#62 : On the Most Reasonable Questions with the Most Clear Answers
Hello, Allow us, please, to think that it is now the right time to set the following, most reasonable, questions and give their respective, most clear, answers: - - - - - - (c) gin&pez@arg (cc-by-4.0) 2019 : start - - - - - - Q1 : Who is "The Common User" and what does it mean "to operate an instrument "facupov" : From A Common User's Point of View" ? A1 : First of all, we welcome in our sow [Small Objective World] "The Common User", that is anyone who wants -as we do- to be able to operate an instrument in at least one useful way for his purposes, without diving too deep into its technicalities, by keeping himself outside of it as much as possible, or to put it on other words : anyone who wants to be able "to operate an instrument facupov : From A Common's User Point Of View". Q2 : Is it possible to operate any VNA "[AnyVNA]" facupov ? A2 : After the completion of our related research here, it seems to us now, more than ever before, that this is possible, as long as he is willing enough, of course, to adopt our just 36 (previously 39) character long description "[LeastVNA]" of [Any VNA], holding perfectly clear in our sow. Q3 : What is the "[LeastVNA]" description of [AnyVNA] ? A3 : That one of an operating [AnyVNA] with a connected one-port load. In this case, the generator of [AnyVNA] produces a primary signal which almost always forces the load to produce a secondary one, except when it has or matching the characteristic value of [AnyVNA], and thus it results to a zero secondary. By construction, [AnyVNA] forms and measures the ratio of the secondary to the primary FAR AWAY from the connected load and delivers it to the user. Because of this distanced measurement, when the user has to measure an unknown load, he has to connect and read not only the unknown one ratio given as g, but also, in addition to that, to connect three 3 known loads : Short, Matching, and Open ones, and measure them as s, l, and o, and then to calculate|compute the unknown value G by using our 36 character long formula: G=(g-l)(o-s)/[(g-o)(s-l)-(g-s)(l-o)] That's all. - No S parameters - No "Errors" - No TDR - No FDR - No Waves - No Pulses - No Reflections - No Incidents - No whatever else - No nothing - Just that: G=(g-l)(o-s)/[(g-o)(s-l)-(g-s)(l-o)] And this is just one of the results of our research in this group. Q4 : Is there a [LeastVNA] of [NanoVNA] ? A4 : Yes, of course, there is our /F/L/O/S/S/ computer program, which is based on the Putty output -in the way most successfully described elsewhere in this group of honorable members- of which the current version was already mentioned at: #59 : UPDATE : [LeastVNA] : version 20191020 /g/nanovna-users/message/5269 20 October 2019 in the wide context of : #50 : The Full Final Report 1 : - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Nominal Values Zinp = ( Rinp , Xinp ) of our Standard [ref2007box], in terms of frequency, using [NanoVNA] and [VNA] - - - - - - - - - - - - - - - - - - - - - - - - - - - - - [NanoVNA] ~ [VNA] Comparison 16 October 2019 /g/nanovna-users/message/5061 and detailed step-by-step in various of our replies to specific questions in this very topic: [errors in "error" models] - Next to come : Explaining Our Full Final Report 2 - - - - end : (c) gin&pez@arg (cc-by-4.0) 2019 - - - - - - - - - - Sincerely, gin&pez@arg 62# |
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Re: Abbreviated documentation for more simplistic tasks?
Anyway, I personally don¡¯t think that it is a good idea to introduce theThis is a nanoVNA affinity group, and Smith is a default display, so edy555 presumably considered it appropriate. nanoVNA shell `data 0` (S11) values can be plotted directly to Smith charts. Those are among this tool's basic attributes. Other formats, perhaps more comfortably familiar to some, are complications to and abstractions from them. |
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Re: Measuring ferrite beads
#test-jig
I have had good luck with this home brew fixture using copper clad, N panel mount connectors, BNC adapters and a flexible conductor wire that can be detached on on side using some old cannon connector pins. I did modify my idea several months ago from reading the three articles mentioned in other posts. It definitely works to distinguish ferrite types.
My findings are that type 31 mix will work as great common mode chokes down to 160 meters and up. Type 43 will attenuate common mode from mid HF up. Spent a few hours going through the door with about 50 mystery ²ú±ð²¹»å²õ/²õ²Ô²¹±è-´Ç²Ô¡¯²õ. My method of marking the beads with a grey marker is finding the 3 dB and 6db points on any given bead and writing the frequency next to them. Run the cal routine with fixture installed. I use the bottom two bnc¡¯s that are pass throughs for the 50 and short load cal. Gary KT7AZ |
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Re: Saving multiple Cal data
In any case to answer the original poster question, reset only affects theThis suggests that, in anticipation of e.g. 'SAVE 2', one should first 'RESTORE 2', then 'RESET'? |
Kurt Poulsen
gin&pez@arg
Oristo
KT7AZ
