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Kirkby calibration kit alternatives?
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hendorog:

--- Quote from: G0HZU on March 01, 2018, 01:17:16 am ---
--- Quote ---Since these come with s-params I grabbed one of them. Shipping is very high, but ultimately still worth it for me to have items which I can use as a calibrated reference.
--- End quote ---

I'm not convinced you can treat the Kirkby kit as some form of calibrated reference if you want to start playing with Cx and Lx factors. I'm not an expert on SMA-SMA connector variability but you can't avoid having a subtle discontinuity between your SMA test cable and the Kirkby SMA cal connector because you can't expect two solid dielectric connections to mate perfectly without a tiny (uncontrolled) air gap and without some form of pin mating variability as well. So I don't know how much this will affect the phase response across a 6GHz bandwidth. A 3.5mm to SMA connection should be a lot better in this respect.

--- End quote ---

Hmm, that is an interesting point and something I don't know enough about to understand how to mitigate.

However, I do have some nice Gore 3.5mm M-M cables (I have been too scared to use them so far) which I can use to mate with the female type standards. Should I get some 3.5mm F-F barrels for the male type standards? I need some anyway as I have an old 8515 test set I want to play around with.

I assume the other side of this is what was used on the other end when they were swept. I can ask the question.
G0HZU:
Also, an SMA female inner expands as it is mated so the Zo (subtly) changes depending on mating depth and male pin diameter. The 3.5mm connector has a solid outer so this problem goes away.

I just think that once you get past 2 or 3GHz you reach the point where you are trying to polish a turd if you want to try and 'calibrate' an SMA based standard using Cx and Lx corrections.

I've always had decent results with my DIY female SMA cal kit but this was only up to the 3GHz limit of my old HP8714B VNA. Also, a lot depends on how accurate it all really needs to be. I suspect that you can get away with using an SMA based cal kit up to 7GHz if you just want to make casual measurements and can accept a lot of uncertainty.

Has anyone tried doing an 'insertable device' calibration using both the male and female parts of the Kirkby kit up to 7GHz and them done some critical tests? Even the basic 6dB attenuator test would be interesting to see.
hendorog:

--- Quote from: G0HZU on March 01, 2018, 02:15:58 am ---Also, an SMA female inner expands as it is mated so the Zo (subtly) changes depending on mating depth and male pin diameter. The 3.5mm connector has a solid outer so this problem goes away.

I just think that once you get past 2 or 3GHz you reach the point where you are trying to polish a turd if you want to try and 'calibrate' an SMA based standard using Cx and Lx corrections.

I've always had decent results with my DIY female SMA cal kit but this was only up to the 3GHz limit of my old HP8714B VNA. Also, a lot depends on how accurate it all really needs to be. I suspect that you can get away with using an SMA based cal kit up to 7GHz if you just want to make casual measurements and can accept a lot of uncertainty.

Has anyone tried doing an 'insertable device' calibration using both the male and female parts of the Kirby kit up to 7GHz and them done some critical tests? Even the basic 6dB attenuator test would be interesting to see.

--- End quote ---

Yes that makes sense. I was going to bypass the Cx Lx issue by doing calibrations offline on a PC where I want the best precision, but it will still be limited.

While on the subject of 3.5mm  - I wonder how much better 3.5mm F-F would they be as cal standards if you used them instead of the SMA F-F bullets in post #86??
The end cap could still be SMA I assume as it won't ever be moved. Do you have any you could sweep?

They are much more expensive of course, 100 USD on digikey/mouser. But still that is cheap in relative terms.



G0HZU:
I've got one at work but someone has borrowed it. Also, I haven't inspected it for quite a while to see how healthy it is. It's very old and has seen a lot of use. I'll try and find it tomorrow.
G0HZU:
OK I found it at work today. I had to walk 1km into a horizontal blizzard to get it as it was being used at another company site :)

It's a 3.5mm F-F connector but not the same grade as the 3.5mm connectors in a typical Agilent cal kit as it uses expanding female contacts rather than the delicate solid centre (with inner petals) as per an Agilent cal kit. So it might not be that much better than an SMA F-F connector, especially as this one is very old and probably quite worn. But I've cleaned it and I'll try it later today. It's really cold and snowy here in the UK and we've been sent home from work early today and told that we don't have to go back until Monday  :)

I'll have an initial look at this connector once my VNA has warmed up.
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