On Fri, 14 Aug 2020 at 01:52, Glen Jenkins WB4KTF <wb4ktf@...>
wrote:
The 50 OHM load (SMA-Male) that came with my nanoVNA-H4 measures 51.13+
ohms. Not a good start for calibration. Where is a good source for GOOD
loads that are accurate?
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Glen Jenkins, WB4KTF, Austin, TX
Do you have a specification in mind? DC resistance doesn¡¯t tell you much,
other than it puts an *upper* limit on return loss. As soon as you go up
in frequency, the return loss will most probably decrease.
If you measure up to 3 GHz, it gives you no idea what it will be like at 6
GHz. Sometimes loads worsen dramatically with frequency, but others, from
the same batch will get better.
The last I looked, there was nothing in the NanoVNA firmware that properly
accounted for the open or short calibration standards. So there are limits
to what you accuracy you are going to achieve if you had a really expensive
load, as the phase errors will kill you.
Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
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Dr. David Kirkby, Kirkby Microwave Ltd