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Re: READING L AN C VALUES USING THE NANOVNAs and the SMITH CHART
On Sun, May 18, 2025 at 11:17 PM, Charles VK1CM wrote:
Makis is a great guy, I have designed one of his products, a dual log detector board, , into a VSWR protection circuit, for my client, after he assured me of its continued availability. Tons of other great, useful products on his site, highly recommended. 73, Don N2VGU |
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NanoVNA-F V3 from SysJoint firmware beep
Hi folks,
I'm brand new here. I just got the NanoVNA-F V3 which is made by SysJoint. Like with my other VNAs (a cheap small NanoVNA-H & a LiteVNA 64) the first thing I looked for was the (custom) firmware situation because the SysJoint NanoVNA-F V3 beeps every now and then and it's no possible to switch this off (I asked the SysJoint support). So I was wondering ... I learned that there's another official manufacturer of the NanoVNA-F, Deepelec, and read that its firmware can be flashed onto a SysJoint NanoVNA-F, too? But has the Deepelec firmware an option to switch any beeping off? Are there other firmwares that can be flashed onto my SysJoint NanoVNA-F V3? Thanks a lot & all the best, Stefan. |
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Re: READING L AN C VALUES USING THE NANOVNAs and the SMITH CHART
On Sun, May 18, 2025 at 11:39 AM, Dan Pate - AI5OL wrote:
Alligator clips are OK if you just want to get a rough idea of the impedance of the device you are measuring. The problem with them is you have an impedance discontinuity from the coax to the clips which can only be partially "calibrated out". Also when you calibrate the clip separation and lead spacing is different that when you are measuring the DUT. This all results in a poor reference plane. Below is a measurement I did of a small inductor. It was tested at 100 kHz. on a DE-5000 LCR meter and then measured using alligator clips and a proper test jig. The results and comments are in the graphs. Roger |
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Re: READING L AN C VALUES USING THE NANOVNAs and the SMITH CHART
On Sun, May 18, 2025 at 02:29 PM, Team-SIM SIM-Mode wrote:
Something wrong with your S11 plot. It should be much better than that. Here is a re-post of my previous plot. S11 is flat but is off by 3 to 4%. Note that S21 is much better estimate at low frequencies but rolls off. Questions ----------- 1. Do you have a photo you can post of your test jig(s) for S11 and S21 measurements? 2. Are you using the enhanced response option in the menu? 3. What version of firmware are you using? 4. Try a 10K and see what you get. |
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Re: READING L AN C VALUES USING THE NANOVNAs and the SMITH CHART
On Sun, May 18, 2025 at 04:13 PM, Roger Need wrote:
An ideal test fixture would maintain a 50¦¸ impedance right to the device body. The Keysight high-frequency SMD fixtures come close to this ideal, the device interface center conductor is a disk, coaxial to and coplanar with a grounded ring which is the outer conductor, with an insulated gap between. The calibration standards and device under test are placed across this gap to make measurements; there is also a shielding cap which bayonets on during calibration and measurements, to stabilize the stray capacitance and add shielding from interference. In the photo the brass thing is the outer ring and the inner electrode is indistinguishable as it is 1 or 2mm across. It would not be to difficult with someone with a lathe, etc. to fabricate a pretty good one. Even a piece of .250" semirigid cable sanded flush would be pretty darned good for small SMD devices or it could be soldered into a ground plane plate flush with the shield for larger components. Other Keysight accessory links, for inspiration: Lower frequency: I used this one a lot for UHF and below: 73, Don N2VGU |
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Re: READING L AN C VALUES USING THE NANOVNAs and the SMITH CHART
On Sun, May 18, 2025 at 09:45 AM, Team-SIM SIM-Mode wrote:
Nizar, The NanoVNA-H4 is only a one-way VNA so it does not calibrate for s22 and S12 and only does six point calibration. In order to get good S21 series measurements you need the source and load impedances to be 50 ohms or you have to do compensation adjustments using an exported Touchstone file. DiSlord has implemented enhanced response which helps somewhat to accommodate for the load impedance. You also need a good test jig because stray capacitance and inductance can affect the results. You need to keep the jig away from the bench to avoid capacitive coupling. Any phase shift errors arriving on port 2 (CH1) will also change the way the resistive and reactive values are computed. I made some measurements today using my jig which I show in the photos below. Below are some measurements using 3.3K and 10K leaded resistors. The NanoVNA was setup to show S11 and S21 at the same time using the same grid scale. The S11 measurement will be 50 ohms high because it is measuring the series resistance of the DUT and the port 2 load resistance. Observations - Both methods were fairly close using the 3.3 K DUT - The 10K had similar results at low frequencies but with the S21 method there was considerable rolloff with frequency. The S11 measurement was fairly flat but was 400 ohms low (4 % off) across the frequency range. Personally the S11 results are good enough for me and I don't have all the fuss associated with an S21 jig and the measurement issues. |
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Re: READING L AN C VALUES USING THE NANOVNAs and the SMITH CHART
I have used mine to measure the inductance of antenna load coils that I have made. I fabricated a test lead that is a coax that terminates in a pair of alligator clips. I clip the leads onto a panel mount SMA connector to attach the Open/Short/Load calibration standards to calibrate to the reference plane at the alligator clips. I can then clip the leads to the connections of the coil to test.
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73 de Dan AI5OL On 5/15/2025 6:18 PM, W0LEV via groups.io wrote:
I've had several requests on reading the values of inductors and capacitors-- 73 de Dan AI5OL --
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Roger Need
Donald S Brant Jr
Stefan Wolfrum
Dan Pate - AI5OL