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