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Confusion over coefficients of open standard in 85050B APC7 cal kit.

Question asked by drkirkby on Jan 16, 2016
Latest reply on Feb 6, 2016 by drkirkby
According to the latest 85050B manual  I can find, the open standard should be an 85050-80010. That's the same part number as listed on the bottom of the box of my old HP 85050B. According to the Keysight web site, the coefficients for the open standard in the 85050B on a PNA are 

* C0=90.4799
* C1=763.303
* C2=-63.8176
* C3=6.4337

(Those are the same as in my 8720D firmware for the 85050B)

My 85050B cal kit, is an older HP model with a Maury Microwave 2616D3 open standard. As far as I can see from looking at my Maury Microwave 2616D3 and a photo of an Agilent 85050-80010 I see on eBay, they look virtually identical - see photos. The shape of the collet pusher, the position of the slots in the side, all look the same. It's hard to believe the RF design of these two parts is not identical. I'm tempted to suspect Maury Microwave make this for Agilent/Keysight, as they did for HP. But when I plot the fringing capacitance from the above Keysight data, against that of the Maury 2616D3 coefficients taken from the data sheet: 

* C0= 92.85
* C1=0
* C2=7.2
* C3=4.3

they differ quite a bit until 3.5 GHz - above 3.5 GHz they are virtually identical. 

Any suggestions as to what's the best coefficients to use with my open? Would I be better using those in my VNA (virtually same as Keysight web site), or creating a user kit with the coefficients from the Maury Microwave data sheet? 

*UPDATE*
I'm even more confused now, after looking at the coefficients of another Keysight kit - the 85031B! The open coefficients listed on the Keysight web site for the 6 GHz economy 85031B APC7 cal kit are *exactly* the same as Maury Microwave list for the 18 GHz 2616D3 open. 

* C0= 92.85
* C1=0
* C2=7.2
* C3=4.3

I don't have an 85031B with its combined open/short standard (P/N 85031-60001), but I see a picture of one recently on eBay and the collet pusher (i.e. the dielectric) looked nothing like that of the Maury Microwave 2616D3 or HP/Agiient 85050-80010. I can't understand how:

* Two open standards which look totally different (open end of Keysight 85031-60001 and Maury Microwave 2616D3) have the same coefficients. 
* Two open standards which look identical (Maury Microwave 2616D3 and Agilent 85050-80010) have different coefficients. 

Someone please tell me I don't  have dementia.

Dave

Edited by: drkirkby on Jan 16, 2016 7:37 PM

Edited by: drkirkby on Jan 16, 2016 7:50 PM

Edited by: drkirkby on Jan 17, 2016 2:15 PM  

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