Re: TDR setup for NanoVNA #tdr, add electrical delay
Thanks for the link, and the hard work you've done on the firmware. 73!
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Re: TDR setup for NanoVNA #tdr, add electrical delay
And here is another link for a very good TDR app note from Agilent:
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On Friday, October 15, 2021, 11:59:12 a.m. EDT, DiSlord <dislordlive@...> wrote: On Fri, Oct 15, 2021 at 08:47 AM, Jason B wrote:
Is it normal to see a bit of a bump where you have a SO239/PL259?
Yes, every cable damage/connectors provide signal reflection and you can see it on TDR Better search info about Time Domain Reflectometry (TDR) for example:
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I came across an Introduction to Network Analysis presentation by Keysight that I thought those new to the VNA might be interested in reading. It covers Transmission lines, S parameters, Smith Chart, VNA architecture, calibration and measurements. A nice slide shows the relationship between complex reflection coefficient, VSWR, return loss and impedance.
It can be downloaded here >>
Roger
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Re: TDR setup for NanoVNA #tdr, add electrical delay
On Fri, Oct 15, 2021 at 08:47 AM, Jason B wrote:
Is it normal to see a bit of a bump where you have a SO239/PL259?
Yes, every cable damage/connectors provide signal reflection and you can see it on TDR Better search info about Time Domain Reflectometry (TDR) for example:
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When using NANO Saver, the cal files can be stored on the PC/laptop, not in the NANO. You can store them permanently on the PC and access them for future use by just reloading them, provided everything is identical to the original cal. At least that's how it works here. Your mileage may vary? Dave - W?LEV On Fri, Oct 15, 2021 at 12:32 PM Andrew Kurtz via groups.io <adkurtz= [email protected]> wrote: I read somewhere that if you use the nanoVNA alone you MUST calibrate on
it, whereas if you use it attached to nanoVNA-saver, you MUST calibrate on
the computer software.
On Oct 15, 2021, at 7:50 AM, AE5SB <snidrv@...> wrote:
Do I need to do both?
I only did the nanovna calibrate
-- *Dave - W?LEV* *Just Let Darwin Work*
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Re: TDR setup for NanoVNA #tdr, add electrical delay
I know this is a wee bit off topic DiSlord, but could you tell me something? Is it normal to see a bit of a bump where you have a SO239/PL259? What does a normal trace look like for a typical RG8X feedline with PL259s? Is there a place where I can get a crash course on cable diagnostics? The reason I ask is because I saw a pretty good bump on one of my traces where a connector should be, it was a few ohms off from 50, so that makes me think I may have messed up soldering a connector. Thanks for your reply!
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On nanovna-saver/README.md at master ¡¤ NanoVNA-Saver/nanovna-saver ¡¤ GitHub <> I have read that the calibration has to be done for the full sweeprange of interest on the NanoVna as well as in NanoVna-Saver.? When you start the Calibration assistant in NanoVna-Saver the textline in bolt is telling about the same.
After the calibration of the NanoVna? then 101 calibrationpoints has to be saved in Slot 0 (Save 0).
As soon as you press "Connect to device" in NanVna-Saver then Segments show 1 (101 datapoints/sweep).
Before you repeat the calibration procedure in NanoVNA-Saver you can determine if you? wish to refine your sweep with more than 101 datapoints
by changing the number in the Segments window of the NanoVna-Saver.
If you change this to 10 then you have 10 x 101 = 1010 datapoints. Then calibrate. Then measure your device.
Now if you wish to zoom in on your data then change your Start/Stop frequency in NanoVna-Saver.
If you like to do a new calibration within the specified frequency range in NanoVna-Saver do not forget to press the Reset button first to erase the previous Calibration data in NanoVna-Saver.
I am doing so as described above, using a NanoVna-H4 and NanoVna-Saver 0.3.9 and it works fine.
Op 15-10-2021 om 13:50 schreef AE5SB:
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Do I need to do both?
I only did the nanovna calibrate
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I'll give it a try
Thank You
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Re: TDR setup for NanoVNA #tdr, add electrical delay
This related to points count, old fw have 101 points and use 256 FFT.
Now used 401 points, and 512 FFT
Also added amplitude compensation (for 256 FFT need use 256 points, for 101 points all others filled by zero)
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I read somewhere that if you use the nanoVNA alone you MUST calibrate on it, whereas if you use it attached to nanoVNA-saver, you MUST calibrate on the computer software.
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On Oct 15, 2021, at 7:50 AM, AE5SB <snidrv@...> wrote:
Do I need to do both?
I only did the nanovna calibrate
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Re: TDR setup for NanoVNA #tdr, add electrical delay
Well, couldn't edit the other post so I'm adding this one. I think I figured it out, you have to change the sweep points to 101 or 201.
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Do I need to do both?
I only did the nanovna calibrate
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Re: TDR setup for NanoVNA #tdr, add electrical delay
Just wondering, something seems different with the TDR workings in the latest firmware. In the 0.5.0 fw if you set the frequency to 100 MHz you had your max cable length on the right side was close to 150 to 200 feet, and a flat linear ch0 trace until you hit the end of the cable. Now this fw seems like you have to jack the frequency way up to get that cable end to move towards the right, and the trace is all kinds of up and down, it's not huge jumps but it's not almost flat like it used to be. This is a pic of what it used to look like on 0.5.0. I'll have to take another pic tomorrow to show what the new fw looks like in transform set up the exact same way.
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Re: Is the phase angle displayed on the nanoVNA a measurement of the phase relationship between voltage and current in the DUT?
On Thu, Oct 14, 2021 at 10:55 AM, Gregg Messenger wrote: Are they related? Is WHAT related?
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Re: Is the phase angle displayed on the nanoVNA a measurement of the phase relationship between voltage and current in the DUT?
"Things can be explained simply and clearly if one chooses to do so . Often times, I find it's best to only use as much complexity as is necessary to sufficiently convey one's thoughts." That's exactly what I tried to do in my nanoVNA presentation. Yes, there are quite a number of formulas, but only those that are really needed. see /g/nanovna-users/files/Presentations/20191220_ON7DQ_NanoVNA_Presentation_English%20V2.03.pdfS-parameters are explained in just three slides (18-20), couldn't make it much shorter than that ;-) Luc ON7DQ
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Karl Jan,
My SAA-2N measures about -12dBm at 8MHz CW, but the signal pulses on and off during the sweep. (It is -12dBm during the on times, measured with an HP8563E SA.)
I am using the Ojisan version of the SAA-2 firmware.
--John Gord
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On Thu, Oct 14, 2021 at 10:38 AM, Karl Jan Skontorp wrote:
I'm still struggling with my faulty nanoVNA SAA-2N :-( In addition to the
SAA-2N I have got a nanoVNA-F, a nanoVNA-H4 and a small "very tiny...". The
other units are working ok, but I really want to get my SAA-2N back in
business! Today I tested the S21 measurements with the SAA-2N. I measured a
18MHz bandpass filter, and the unit seems to work ok in this mode :-)
The next thing I wanted to check was the level of the "output signal" on Port
0. I also have a handy spectrum analyzer, the tinySA. I put the SAA-2N in "CW
mode" at a frequency of 8MHz. Connected the tinySA and observed a lot of
harmonics, but the "main peak" was at about -23dBm!!! I think this level is
too low! I did the same measurement on the H4 - result -8dBm and the
nanoVNA-F had +3dBm. The result on the "very tiny..." was -7dBm.
When putting this together, I my first thought was the Si5351, but when I have
done the rest of the measurements, I think one of the RF-switches, MXD8641,
must be broken. Can someone please tell me if my assumptions correct?
Will be grateful for any response!
Karl Jan - LA3FY
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For swr plot you can use the value of 6:1 each side of center freq. Find those 2 values of freq, find their difference and divide into the center freq to get operating Q. If you double that value, that should be close to your so called design Q.
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"the logmag is extremely narrow and touchy to be resonant"
Yes, that one. And you should be seeing a pretty decent return loss value.
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You will be measuring S11, a one port measurement. Set the display for log magnitude dB. So the sweep should show an excellent return loss at the desired frequency set for the PI MATCH, say 7.1 MHz for the 40 meter band. The value of the return loss might be 20 dB or better, it will be clearly a notched like response. See the picture of what I obtained on my amplifier. Your sweep should be similar. I think I was running the sweep over a span of 5 or so MHz at 7, or 5 to 9 MHz for the 40 meter band.
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Re: Is the phase angle displayed on the nanoVNA a measurement of the phase relationship between voltage and current in the DUT?
That¡¯s a good way to put it Roland.
Thanks for the link.
--
VE6WGM
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Roger Need
Jim Allyn - N7JA
Gregg Messenger VE6WGM