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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.

On Fri, Oct 4, 2019 at 02:49 AM, sala nimi wrote:

Homemade terminator was dot or comma in the Smith chart but commercial one had
a clear arc.

probably it just means that you calibrated your VNA with bad terminator. So, now it shows good terminators as bad, because they are not bad as one which is used for calibration :)

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

Take a look at this:



I've ordered a $18 SOL kit from ebay. I'll be adding comparisons to the Anritsu to the thread when they come in. I'll drag the 8753B to where I can power it up for that. So I'll have TDR to 20 GHz and VNA to 3 GHz.

The more I use my Tek 11801 the more I wish that there was a cheap sampling scope that would work with one of Leo Bodnar's pulsers. While the 20 GHz of an SD-24 or SD-26 would be very difficult to match, one might be able to get to 5-6 GHz with a clever design which was cheap to make using modern parts.

The great thing about the time domain is you can tell which part in a series of connectors is doing what.

Have Fun!
Reg