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Kirkby calibration kit alternatives?
G0HZU:
I think your problems may be due to the type of VNA you are using. I've not seen one of those models before and it may have quite poor performance.
Can you post up your Kirkby cal kit correction file or list its corrections for Cx and delay etc?
I tried creating a model based on the default corrections for delay and Cx on his website here:
http://www.kirkbymicrowave.co.uk/support/Kits/85033/
...and then I compared this to the OPEN S1p file I found in your zip files. I assume this S1p file came from Dr Kirkby as it looks like a decent measurement to me. When I compare my model to his s1p file the phase response is very good. I'm using the Cx and delay from the web link above but you may have a tweaked version of this with your cal kit? Either way the phase response is very good and I won't post it up here because I don't want to give the impression I can measure this stuff more accurately than DrKirkby. But I will say that the results are very close! Not much to worry about here I think..
I also looked at the SHORT s1p file and the results are very close to the model that is based on his default cal kit corrections on the website. This is very good indeed and it kind of shows that the SHORT in his kit is a good one I think.
I can suggest subtle differences in the default Cx corrections but you probably have this info already. His kit data looks VERY good to me :)
Bud:
Do not use crappy Chinese connectors directly on your VNA connectors, you will be sorry but it will be late.
"Less quality cal kit" - Dr. Dunsmore of HP/Agilent/Keysight, the 8753 designer, was saying he could calibrate a VNA using a brick, as long as the brick is accurately characterized with calibration coefficients.
G0HZU:
--- Quote ---"Less quality cal kit" - Dr. Dunsmore of HP/Agilent/Keysight, the 8753 designer, was saying he could calibrate a VNA using a brick, as long as the brick is accurately characterized with calibration coefficients.
--- End quote ---
I think my Ecal module 'works' because it has a lot of correction coefficients. Otherwise it would be only useful as a paperweight...
G0HZU:
--- Quote ---what i concluded from your reply #35 and #36 is, are you suggesting that using less quality cal kit in the same VNA will result in more ripple? if that is the case, there is possibility that kirkby did the attenuator report using agilent cal kit as his calibration standard? i'll need to confirm this back to him.
--- End quote ---
For sure you will get more ripple with an inferior cal kit or with one that has not been corrected properly. I can make my ENA VNA look REALLY bad if I deliberately use a poor cal kit.
But I think the Kirkby kit looks OK based on the bundled S1p files. The SHORT, OPEN and LOAD s1p files look very good to me against a model based on the default cal kit data. Assuming you are setting up the transmission calibration correctly you should get very good results with minimal trace ripple in the S21 and S12 attenuator test.
Note that I don't get as good a phase response as that from an Agilent/Keysight 85033 kit though. I get a virtually perfect flat phase line with the Agilent 85033 kit for the OPEN if I use the Agilent cal corrections for Cx etc in my comparison model. Note also that I'm just doing this in my workroom at home and using an RF simulator to create the comparison model. But my model seems 'perfect' when compared with the decent $$$ Agilent cal kit data and a measurement of a real 85033 cal kit on an HP8753ES as I get a flat line for the phase as per the second plot in post #15 :)
I'd be happy to review a Kirkby cal kit and I now suspect the results will be better than I first thought. However, I'd be giving it some fairly strict tests, way beyond this simple 3dB attenuator test. I'll try and borrow one of these kits from my ex colleague and put it through its paces :)
G0HZU:
I created a flawed DIY SMA cal kit correction file with performance similar to the phase plots in post#37 and see below for the result of the 3dB attenuator test after my VNA was calibrated with the same DIY SMA cal kit but it now has flawed correction data for Cx and Lx.
You can see that the response has ripple above about 4GHz. Note that this has the thru delay correct and also has the loss and the basic delay correct up to about 3GHz. So it works quite well up to about 3GHz.
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