On Fri, 4 Oct 2019 at 00:49, sala nimi <sala.nimi@...> wrote:
I had some time and tested some terminators for fun. I thought that
commercial terminators are nearly perfect, but not mine. I have a N
terminator perhaps from Digikey, and It was worse than my very old self
made terminator from UKW berichte or VHF communication. Homemade terminator
was dot or comma in the Smith chart but commercial one had a clear arc.
But so much depends on what you use to perform the calibration with. To
take an extreme example
* 50 ohm system
* Load used for calibration has an impedance of 30 ohms
* DUT #1 is a resistor of 49 ohms
* DUT #2 a resistor of 31 ohms.
Although the 49 ohms resistor has a much better return loss in a 50 ohm
system than the 31 ohm resistor, the VNA would indicate the opposite
because it was calibrated with a load close to DUT #2.
It is very easy to fool yourself with VNA measurements.
Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
Telephone 01621-680100./ +44 1621 680100
Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United
Kingdom
