Phase angles and imaginary parts were not in the scope of what I was checking. That is why I made the measurement at 500 kHz. And I do not own a real high end VNA, HP or otherwise. So I cannot help you there.
The point is, I am very sure NanoVNA will not track a $75,000 VNA with 0.1 dB precision. There are many, many users, perhaps most users, however who will derive great utility from this $55 device even if its accuracy is only 1 dB or even 5 dB. I also would expect significant variance from unit to unit so that even from unit to unit the accuracy would not track at that level.
I would not discourage your intellectual exercise but would only point out that for most here it is irrelevant.
WA8TOD
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On Aug 12, 2019, at 10:30 AM, tuckvk3cca <tuckvk3cca@...> wrote:
Have you got the phase angles or imaginary parts? Can you compare the readings with your HP analyzer? Comparing with the VOM values can be misleading. Reason is I don't believe the SA612 detectors are good to 0.1dB magnitudes. The AD8307 is good to 0.3dB at best and its a much better chip. Secondly as the Return loss goes down the uncertainty in resistance increases e.g at 0dB the resistance can be either zero or infinity. To narrow this gap requires very accurate phase angle measurements. Again the smallest phase error can lead to large uncertainties. I don't think its conservative to not accept any impedance values from the nano when return loss is less than 1dB.Sent from my Samsung Galaxy smartphone.
-------- Original message --------From: Warren Allgyer <allgyer@...> Date: 12/08/2019 14:56 (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Measurement of high impedance loads I am not sure I understand the question.The NanoVNA can certainly indicate down to 0.1 dB, so it can measure there. The accuracy of that measurement would be subject to the accuracy of the calibration and the inherent accuracy of the instrument. Personally and for my purposes, absolute measurements of RL to the 0.1 level are not very interesting so long as the instrument is capable of directional changes at that incremental level. The NanoVNA certainly indicates in 0.1 dB increments and that is more than enough for my purposes.WA8TODOn Aug 12, 2019, at 8:37 AM, tuckvk3cca <tuckvk3cca@...> wrote:I have added the vswr and the return loss. Can the nano measure down to 0.1dB return loss?Sent from my Samsung Galaxy smartphone.-------- Original message --------From: Warren Allgyer <allgyer@...> Date: 12/08/2019 13:55 (GMT+01:00) To: [email protected] Subject: [nanovna-users] Measurement of high impedance loads Earlier there was a comment in one of the threads asking if anyone had measured the accuracy at high values of resistance. Here are four data points I measured this morning. The measurements were done at 500 kHz in order to minimize the reactance of the test fixture which was a pair of binding posts on a BNC adapter. The first value is the actual resistor value as measured on a VOM and the second is the value indicated by the Smith Chart on NanoVNA. 810 ohms - 810 -16.2-1.08dB1500 ohms - 1500-30-0.58dB2980 ohms - 2880-57.6-0.3dB8100 ohms - 7940-159-0.11dBWA8TOD
Warren Allgyer