Beware of cheap underperforming clones

As of 2023 there are many badly performing clones on the market. V2/3GHz NanoVNA uses parts like ADF4350 and AD8342 which are costly and clones have been cutting costs by using salvaged or reject parts.

See official store and look for V2 Plus4/V2 Plus4 Pro versions only to avoid getting a bad clone. We have stopped selling V2.2 versions since October 2020, so all V2 hardware that are not Plus or Plus4 are not made by us and we can not guarantee performance.

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10dB attenuator to lower output power, is it ok?


Leif M 2024/11/19 11:15

A  quick question. Before I make mess of my calibrations, can I lower the S11 output power with an attenuator. Can I still measure amplifier inputs at 1-5MH. After calibration  that is.

Leif M 2024/11/20 00:05

No  quick questions or answers.
I tired waiting and tried it myself. I measured 150pF, 270 ohm  and 18 ohm components,  and got good results. I used low frequency, less than 5MHz , because that is easier.

Brian Morrison 2024/11/20 17:46

On Wed, 20 Nov 2024 00:05:15 -0800
"Leif M via groups.io" <leif.michaelsson=gmail.com@groups.io> wrote:

> No  quick questions or answers.
> I tired waiting and tried it myself. I measured 150pF, 270 ohm  and
> 18 ohm components,  and got good results. I used low frequency, less
> than 5MHz , because that is easier.

The simple answer is that you can put the attenuator in but it will
reduce the dynamic range of an S21 measurement by 10dB and the dynamic
range of an S11 measurement by 20dB. This is after calibration.

This may be suitable for your purposes.

--

Brian Morrison

Leif M 2024/11/21 10:02

I understand that, but it is unclear what it means when I am  measuring gain and input impedance. I am not measuring  ultimate attenuation, duplexers or anything such.

Brian Morrison 2024/11/22 22:32

On Thu, 21 Nov 2024 10:02:22 -0800
"Leif M via groups.io" <leif.michaelsson=gmail.com@groups.io> wrote:

> I understand that, but it is unclear what it means when I am
> measuring gain and input impedance. I am not measuring  ultimate
> attenuation, duplexers or anything such.

You are removing the effect of the attenuator on the measured S21
and S11 numbers by calibrating with it in place. The values you get will
be correct unless they are now too close to the detector noise levels
that are increased by the attenuator because the detectors see less
signal and hence a lower SNR. As a result the errors in the measurements
increase but perhaps not enough to cause them to be noticeably
inaccurate for your purposes.

--

Brian Morrison

Leif M 2024/11/23 04:20

Yes, there is a bridge somewhere inside the VNA, signal can get low.

Perhaps next version of the VNA could have a switchable attenuator. It would help with testing amplifiers. (There will be a next version?  I hope)

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