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Re: Read polar impedance (Ohms and phase) directly?
On 7/23/22 8:41 AM, Ed G8FAX wrote:
The S1P files contains the real and imaginary parts of the reflection coefficient, Greek letter ¡®gamma¡¯.in Excel, IMARGUMENT returns the angle (in radians), IMABS is the magnitude |
Re: Read polar impedance (Ohms and phase) directly?
I can do the math.... I taught electronics including L - R- C circuits and conversions for 17 years. I was just looking for a quick way to find them on the Nano. And |Z| was my main interest.
Although I must say, the equations shown in the pdf look nothing like what I taught.... Mine was simply going back and forth between R +jX and Z ¦¨, normally using Pythagoras and trig functions. I fired up a laptop with NanoVNA Saver and was able to get what I needed. Thanks to all. |
Re: Read polar impedance (Ohms and phase) directly?
The S1P files contains the real and imaginary parts of the reflection coefficient, Greek letter ¡®gamma¡¯.
The complex impedance Z is given by Zo * (1+gamma) / (1-gamma) Excel has the capability of working and manipulating complex numbers, so the spreadsheet formulae can be simplified and use directly the values from the S1P file. I believe complex number feature also exists in LibreOffice. To obtain the impedance magnitude after this requires conversion to polar form. ATAN2 is a useful function to use. Kind regards Ed, G8FAX |
Re: Read polar impedance (Ohms and phase) directly?
On 7/22/22 10:50 PM, F1AMM wrote:
Admitting that it is of interest to examine the phase of the impedance, it is indeed necessary to start from the Touchstone S11 file (.s1p). It is an ASCII file where you find, on each line: the frequency, the real of the S11 then the imaginary of the S11. in the first line there is the standardization impedance (50 Ohms in general)You could just post a sample excel file.. (of maybe the first 10 lines of a S1P). That's what I've done. |
Re: |S11| > 1
Interesting discussion. I used to work for HP. Later sold Cascade probe stations. Calibration was always "difficult". Especially on wafer: how far do you overdrive (i.e. press the probe down), how many times has that standard been used, etc etc.
Seems to me we're expecting a bit too much from the nanovna. As someone already posted, its not a lab grade instrument. To me its a "how close am I" kind of tool. If I REALLY care I will use a better tool (I am fortunate enough to have an 8753). Ron N4XD |
Re: Where to buy Genuine Nanovna
Hi Wayne,
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Mark at QSL Communications sells several VNAs including the Hugen NanoVNA-H and the Deepelec NanoVNA-F (now DeepVNA-101). This is the VNA page Do your homework on overseas vendors. Cheers...Bob VK2ZRE On 1/07/2022 12:57 am, wayne@... wrote:
Hi all, it¡¯s been a while since I followed this group but perhaps somebody can suggest the best place to buy a genuine Hugen NANOVNA. H4 |
Re: |S11| > 1
F1AMM
I've written a Windows utility that checks Touchstone files for |S11| > 1. It handles versionThanks a lot. README.TXT is only for GND.EXE Do you have help files for AVG.EXE and S11.EXE? -- F1AMM Fran?ois -----Message d'origine-----De la part de Brian Beezley Envoy¨¦ : samedi 23 juillet 2022 02:12 |
Re: Read polar impedance (Ohms and phase) directly?
F1AMM
Admitting that it is of interest to examine the phase of the impedance, it is indeed necessary to start from the Touchstone S11 file (.s1p). It is an ASCII file where you find, on each line: the frequency, the real of the S11 then the imaginary of the S11. in the first line there is the standardization impedance (50 Ohms in general)
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If you are interested, I have restored the "formulas" allowing you to recalculate the A+jB of the load from S11. It's not trivial even if it's quite simple if we start from the right bases. I do this in Excel. I don't know how to pass this type of information on the forum. -- F1AMM Fran?ois -----Message d'origine-----De la part de Roger Need via Envoy¨¦ : vendredi 22 juillet 2022 18:22 |
Re: |S11| > 1
I've written a Windows utility that checks Touchstone files for |S11| > 1. It handles version 1.1 files, the kind NanoVNAs generate, as well as version 2.0. It lists maximum |S11| and the number of frequencies where |S11| > 1. This utility may come in handy if you experience odd problems processing NanoVNA data as I did.
Just download the ZIP, extract the files, ignore the ground probe stuff, put S11.EXE in a directory containing Touchstone files, and double-click on it. Brian |
Re: Common ground and 2-port measuring
Try to connect through any free VPN, pointing to Netherlands... They can!
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El jue., 21 jul. 2022 16:48, Ed G8FAX <ed@...> escribi¨®:
On Wed, Jul 20, 2022 at 05:42 PM, Dragan Milivojevic wrote:site |
Re: Read polar impedance (Ohms and phase) directly?
On Fri, Jul 22, 2022 at 08:59 AM, Neil Preston W0NRP wrote:
I assume when you say "lumped impedance and phase angle" you mean display |Z| (sqrt of [r^2+X^2]) and impedance phase angle. The NanoVNA and the two popular PC programs (NanoVNA Saver and NanoVNA app) can calculate and display |Z| but do not have an impedance phase angle display capability. The "phase" option in the trace menu is the reflection coefficient phase angle which is not the same thing as impedance phase angle. The polar display is for the reflection coefficient not impedance. The easiest way to calculate the impedance phase angle is to import the Touchstone S11 file into a spreadsheet and do the calculation and plotting there. Roger |
Re: At which point do we take the value of impedance to tune an antenna?
On Fri, Jul 22, 2022 at 04:34 AM, Diane BONKOUNGOU wrote:
You never posted in the other topic what you finally did to correctly measure the antenna with the NanoVNA. If you don't establish the "reference plane" rightat the antenna your impedance measurements will be way off and you won't be able to design a matching network. Even if you get a decent "reference plane" the antenna must be measured in circuit so that you have a the same ground plane as when the antenna will be used. Also the outer shield of your test cable may form part of the antenna and this will affect the measurements. At these GHz frequencies you will have better results if you tune the antenna for resonance at the desired frequency instead of building a matching network. The reason I say this is that VSWR and Return Loss will only change slightly if your reference plane is not right on but the impedance will be off a fair amount. The reason is that the magnitude of the reflection coefficient stays the same and only the phase angle changes if the cable is slightly long or short. However the phase angle rotation results in a different impedance calculation. Even if you get a reasonable estimate of impedance you then have the issue of designing with components and PCB design at Bluetooth frequencies. Roger |
Read polar impedance (Ohms and phase) directly?
I am trying to figure out if the Nano can display the lumped impedance and phase angle numerically without having to calculate from r + jX. I expected to read that from the POLAR menu, but some searching reveals that is just a coefficient from -1 to +1.
??? |
Re: At which point do we take the value of impedance to tune an antenna?
On 7/22/22 8:36 AM, Zack Widup wrote:
You should measure the impedance at the frequency you plan on using. I haveMost simple antennas, near their design frequency, have an impedance curve that looks a lot like a RLC resonance. The real part changes fairly slowly, but the imaginary part changes quickly. On the attached graph (impedance of a dipole), you can see that X changes from about -40 to +40 going from 90 to 100% of a half wavelength (resonance is at about 95% half wavelength), while R goes from 53 to 75 ohms over the same frequency range. A 5% variation in frequency isn't huge (at 2.45 GHz, 5% is 120 MHz) - If you think of the antenna as a filter, it's not even down 3dB at 5%. Zmag is the absolute value of the Z. So if you put a L or C in to "cancel" the reactive part, |
Re: Common ground and 2-port measuring
On Fri, Jul 22, 2022 at 06:14 AM, Miro, N9LR wrote:
Good, let us know how you get on with them, I'm sure there are others interested in using baluns with the nanoVNA. Kind regards Ed |
Re: At which point do we take the value of impedance to tune an antenna?
You should measure the impedance at the frequency you plan on using. I have
found fairly large variations over a few MHz in this range before. Zack W9SZ On Fri, Jul 22, 2022 at 6:34 AM Diane BONKOUNGOU <dianebonk2@...> wrote: Hello,<> Virus-free. www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> |
Re: At which point do we take the value of impedance to tune an antenna?
Diane BONKOUNGOU
Hello Douglas,
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Thanks for your response. Best regards Le ven. 22 juil. 2022 ¨¤ 12:55, Douglas Butler <sherpadoug@...> a ¨¦crit : What matters is the impedance of the antenna at the frequency where you |
Re: Antenna pi-network matching High or low pass ??
On 7/22/22 2:00 AM, Diane BONKOUNGOU wrote:
Hi all, I am a beginner in RF system design and have some questions.Folks will chose high or low pass to meet spurious emission requirements. For instance, if your transmitter has 3rd harmonic, using a low pass matching network can help knock that down to below the (typical) -40 dBc or -60 dBcrequirement. As to why you might want to pass DC - AC coupled ungrounded antennas can build up static charge. If you don't have some way to discharge that static, then if the voltage gets high enough, you might have a spark (which generates broadband RF power) or a component failure (e.g. a capacitor exceeds its voltage rating). Some antennas though, are inherently grounded, so in that case, you don't care. |
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