Re: US based Ebay seller claims he is selling v3.4 NanoVNA - true?
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Re: US based Ebay seller claims he is selling v3.4 NanoVNA - true?
On Tue, Feb 11, 2020 at 04:10 PM, <nanovnagroup@...> wrote:
But in the mean time if any of you eagle eyed guys want to take a shot at this and see if this is really a v3.4 unit here it is:
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The v3.4 NanoVNA-H has a 650 mAH battery and 0 dBm RF out. The ebay listing appears to be v3.3 from its specifications.
- Herb
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Re: US based Ebay seller claims he is selling v3.4 NanoVNA - true?
More negative reviews than I would like to see and many of them appear pretty serious.
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US based Ebay seller claims he is selling v3.4 NanoVNA - true?
I asked this "US Ship" ebay seller straight up and he replied that yes, his NanoVNA has in fact a v3.4 PCB. I also asked this morning on a follow up message if he could post some pictures of the PCB showing the v3.4 label on it, but so far have not heard back. Maybe he'll answer by tomorrow as he did yesterday.
But in the mean time if any of you eagle eyed guys want to take a shot at this and see if this is really a v3.4 unit here it is:
Please post any comments and opinions about it here.
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Re: Frequency and steps accuracy
Thank you everybody who answered my question. I got the answer I wanted.
73/Torbjorn
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11 feb. 2020 kl. 22:10 skrev pgc1682@...:
Hi,
Interpolation problem not only nanovna exist.
If you use nanovna saver 10 segment = 1010 points data. But another interpolation errors occured, because double calibration not ok.
Nanovna saver 1010 point calibration fully ok when use raw data and calibrate all point in nanovna saver, not use pre calibrated and interpolated instrumet data. I requested this method. I think scanraw command the key.
73,
Lajos
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Hi Kurt,
That would be nice!
My nanovna-h and the torque wrench are not shipped yet. At the flea market in Rosmalen (NL) I will look for leads (hope for Huber Suhner for reasonable prices) and adapters and pieces to make SOL for bnc and PL.
Downloaded also the 1.5 version of the manual from Gunthard Kraus (Danke, Gunthard!)
Best regards,
Robert Glerum PA7RG
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Re: Frequency and steps accuracy
Hi,
Interpolation problem not only nanovna exist.
If you use nanovna saver 10 segment = 1010 points data. But another interpolation errors occured, because double calibration not ok.
Nanovna saver 1010 point calibration fully ok when use raw data and calibrate all point in nanovna saver, not use pre calibrated and interpolated instrumet data. I requested this method. I think scanraw command the key.
73,
Lajos
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Re: Frequency and steps accuracy
See Erik's msg # 10886 for why a 101 point calibration performed using a wide frequency span, may not be accurate when applied to a 101 point measurement in a different frequency span.
- Herb
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Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)
Greetings, Using the "NanoVNA-Saver" PC app to control my mid quality nanoVNA I spent considerable time testing the high impedance measurement accuracy. I had previously made up a variety of loads using paralleled 0805 SMD resistors mounted on the back of BNC PCB through hole connectors. Thus with my loads I needed to use an SMA/BNC adapter which added a slight amount of shunt C which I subtracted out of the results. In a nutshell I found my nanoVNA is quite accurate, within about 2%, for loads up to 1K Ohm for 2M measurements. Thus I think if used properly your nanoVNA should work well for measuring a 300 Ohm load. You may find this thread of interest: /g/nanovna-users/message/2146?p=,,,20,0,0,0::relevance,,VA7TA,20,2,0,33508471 The folded dipole measurement case presents a balanced load the unbalanced input of the nanoVNA. This may upset the balance and introduce an error. You could consider making a 4:1 half wave coaxial balun (See Attached) that would provide you an unbalanced measurement point for the nanoVNA and would step the impedance down to the the 75 Ohm region. It would allow you to use a relatively long RG58 coaxial test lead that would facilitate making the measurement a wavelength or two away from the dipole to reduce any antenna coupling proximity effects. Prior to making the measurement you would need to extend the calibration reference to the antenna unbalanced balun interface end of the long test lead using the usual SOL calibration procedure. -- Enjoy! Tom VA7TA
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Re: Frequency and steps accuracy
Unless you understand why it should work you should always recalibrate when changing frequency span. Search the group for longer explanation In short. A linear interpolation in two dimensions between two points on a circle can create a massive error -- NanoVNA Wiki: /g/nanovna-users/wiki/homeNanoVNA Files: /g/nanovna-users/filesErik, PD0EK
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Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)
Somewhat longer answer Calibration creates a set of known calibration data points. 101 in total Any frequency used during measurement that does not uses exactly one of these calibrated data points uses interpolated data. If the calibration points are far apart the interpolation can have huge errors!!!!!!!! So, if in doubt. Recalibrate!!! -- NanoVNA Wiki: /g/nanovna-users/wiki/homeNanoVNA Files: /g/nanovna-users/filesErik, PD0EK
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Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)
Best is to ALWAYS calibrate the device for any measurement using exactly the same frequency span you are using in the measurement. Only when you know why it should work you are allowed to use a previous calibration with somewhat different frequency span. If in doubt recalibrate! -- NanoVNA Wiki: /g/nanovna-users/wiki/homeNanoVNA Files: /g/nanovna-users/filesErik, PD0EK
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Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)
Ok, I am still on a steep learning curve.
Are you saying that if I am working with the 2 M and I should set the upper and lower limits before calibrating?
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Re: Frequency and steps accuracy
Thanks for your response Gyula. However as I wrote the frequency step will change if I change frequency range. In my example case the step changes from 9 MHz to 90 kHz each, that is a change that corresponds to the change of stop frequency from 900 MHz to 9 MHz. And the question remains what happens with accuracy in the lower range, now 50 kHz to 9 MHz, still with 101 steps. And yes, I know very well how to calibrate. I know that I can do many things with various PC software, but right now I am concerned with the NanoVNA itself.
73/Torbjorn
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11 feb. 2020 kl. 16:29 skrev Gyula Molnar <gyula.ha3hz@...>:
When you pick up the frequency range, you determine the location of the steps - you will get a wrong result without calibration. So after recording each frequency range, first Reset, then Calibrate and finally save if you need the range later. Q-0.4.4 performs averaging, which must be selected before calibration. After selecting a new range, first Reset, then Calibrate and then save to a memory location. (0-4)
You can take several steps if you use nanoVNA-Saver. With the nanoVNA-Saver, you can record, calibrate, measure and save countless quantities and save it to your PC.
I hope I was able to help you.
73, Gyula
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Re: Frequency and steps accuracy
When you pick up the frequency range, you determine the location of the steps - you will get a wrong result without calibration. So after recording each frequency range, first Reset, then Calibrate and finally save if you need the range later. Q-0.4.4 performs averaging, which must be selected before calibration. After selecting a new range, first Reset, then Calibrate and then save to a memory location. (0-4)
You can take several steps if you use nanoVNA-Saver. With the nanoVNA-Saver, you can record, calibrate, measure and save countless quantities and save it to your PC.
I hope I was able to help you.
73, Gyula
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Frequency and steps accuracy
Here is a question for fw programmers and hw specialist. I am using a NanoVNA-H with Hugen fw 20200118. If I have made a calibration for 50 kHz to 900 MHz I get a frequency step of 8,999 or 9,000 MHz. If I now change the stop-frequency to 9,000 MHz and make no new calibration I get a frequency step of 89 or 90 Hz. Obviously the frequency step is always span divided by 101. The question is: Do I loose any accuracy in display and calculations with the narrower span without making a new calibration? I think that the answer is not as obvious as it might seem.
73/Torbjorn
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Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)
If for 2m, please calibrate between 140 and 150 MHz (or narrower), as we have only 101 points and no smooth interpolation between those points occurs - due to limited storage of the device. Generally, always calibrate with as small as possible difference between lower and upper frequency just as suitable for your application. If you had calibrated between 50k and 900 MHz, you are way off in the 2m band, as the points are spaced by some 9 MHz. If you need more points, you could connect it to a computer and use NanoVNA saver. You need to recalibrate whenever you switched off/on and don't make use of a well suitable saved cal. 73, Hans DJ7BA -----Urspr¨¹ngliche Nachricht----- Von: [email protected] < [email protected]> Im Auftrag von Kayak Gesendet: Dienstag, 11. Februar 2020 08:54 An: [email protected]Betreff: Re: [nanovna-users] nanoVNA Maximum Impedance Measurement (Folded Dipole example) Im new to this, but wondering how often does the nano need calibrating? Can it be calibrated all freq at once or has to be in segments? Does the cal have to be "saved"??
On Tue, Feb 11, 2020 at 12:09 AM Bob Albert via Groups.Io <bob91343@...> wrote:
I think it's a calibration issue. My nano measures accurately over a wide range of values. It sort of gets sloppy over a few thousand Ohms of resistance. Good up to at least 10 microfarads.
The trick is to use precise SOL parts and reset the nano before calibrating. The readings you get are all based on believing that the Load calibration is 50 Ohms; that's the standard with which it compares the unknown.
Bob
On Monday, February 10, 2020, 08:57:59 PM PST, simpson.s1917@... <simpson.s1917@...> wrote:
Hi there
Question: What is the maximum impedance capable of being measured via a nano VNA?
Context: I am working on an impedance matching section (1/2 wave length of coax) for a folded dipole antenna (VHF 2m amateur radio band). How ever when I measure the impedance of the folded dipole it returns a value of approximately 25 Ohms, not the 300 Ohms expected.
Some further testing with Resistors shows the impedance value error seems to increase significantly around 150-200 Ohms. 200 Ohms (2x100Ohm resistors) results in a measured value of approximately 140 Ohms.
Has anyone else experienced this same issue or have some more information on this?
It is very possible my aerial construction is off but wanting to
explore this, and haven't found a good source on maximum R,X
specifications for the nanoVNA
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Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)
Im new to this, but wondering how often does the nano need calibrating? Can it be calibrated all freq at once or has to be in segments? Does the cal have to be "saved"?? On Tue, Feb 11, 2020 at 12:09 AM Bob Albert via Groups.Io <bob91343@...> wrote:
I think it's a calibration issue. My nano measures accurately over a wide range of values. It sort of gets sloppy over a few thousand Ohms of resistance. Good up to at least 10 microfarads.
The trick is to use precise SOL parts and reset the nano before calibrating. The readings you get are all based on believing that the Load calibration is 50 Ohms; that's the standard with which it compares the unknown.
Bob
On Monday, February 10, 2020, 08:57:59 PM PST, simpson.s1917@... <simpson.s1917@...> wrote:
Hi there
Question: What is the maximum impedance capable of being measured via a nano VNA?
Context: I am working on an impedance matching section (1/2 wave length of coax) for a folded dipole antenna (VHF 2m amateur radio band). How ever when I measure the impedance of the folded dipole it returns a value of approximately 25 Ohms, not the 300 Ohms expected.
Some further testing with Resistors shows the impedance value error seems to increase significantly around 150-200 Ohms. 200 Ohms (2x100Ohm resistors) results in a measured value of approximately 140 Ohms.
Has anyone else experienced this same issue or have some more information on this?
It is very possible my aerial construction is off but wanting to explore this, and haven't found a good source on maximum R,X specifications for the nanoVNA
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Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)
Good luck and please let us know what you find.
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On 11/02/2020 10:36, simpson.s1917@... wrote:
Thank you both for the replies.
I only have the default calibrations
(SMA) ones currently (working on making some other ones, PL259, etc) So my
nanoVNA was calibrated at the onboard SMA port, The measurements were made
through an SMA to PL259 Adaptor with (100mm) of coax.
I will try the
measurements again once I get some better and additional calibration
standards sorted.
Thanks both for the input
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Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)
Thank you both for the replies.
I only have the default calibrations (SMA) ones currently (working on making some other ones, PL259, etc) So my nanoVNA was calibrated at the onboard SMA port, The measurements were made through an SMA to PL259 Adaptor with (100mm) of coax.
I will try the measurements again once I get some better and additional calibration standards sorted.
Thanks both for the input
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Gyula Molnar