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| Kirkby calibration kit alternatives? |
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| hendorog:
--- Quote from: Mechatrommer on February 22, 2018, 05:28:57 am --- fwiw, among other things, attached is attenuator plot provided from Kirkby to me. the result i got on my VNA is much noisier... --- End quote --- He has reduced the IF bandwidth from the default. That would reduce the noise. What VNA have you got? |
| Koen:
--- Quote from: technogeeky on February 21, 2018, 11:02:34 pm ---I just wanted to point out these male SMA references available for about $20 in the USA. They manufacturer link goes back to mRS miniVNA Tiny and Pro's website. After more and more searching, it seems like these guys are the manufacturer --- End quote --- Amphenol 132360, 132331, 202112 maybe. I have both the kit you linked and these very-cheap three but I'm not knowledgeable enough to say anything except they look very similar. |
| technogeeky:
--- Quote from: hendorog on February 22, 2018, 06:36:29 am --- --- Quote from: technogeeky on February 22, 2018, 05:17:39 am ---Does anyone here know how long it would take to record all of the relevant calibration coefficients, if someone purchased a open-short-load and sent it to another forum member with access to a good/great VNA? At the end of the day, when is the modeling necessary? If it's only when you are making your own and trying to improve your design of DIY devices, then we can just bypass that step and send devices to people who can make the measurements for a small fee? --- End quote --- Yes the modelling would not be required to transfer a calibration from someone elses' cal kit. In theory, all you need to do is send them the items you want to use as calibration standards and adapters. They just need to generate an S parameter file for each one on their calibrated VNA. Then you run it through the script to determine the coefficients. How well that step works is unknown. If you also sent a decent attenuator then that could be used to compare your new calibration with the calibration of the other user. So they would need a VNA and a good cal kit. Then they would do a calibration first, and then make 5 or 6 measurements, transfer them to a PC and email them. Then ship back the items. --- End quote --- I don't even own a VNA (though some day I would like to). But I would like information on how good a particular cal kit is, so I can understand the limitations of what measurements I can make with e.g. spectrum analyzer with tracking generator (where you normalize, so this is less important); but more importantly what the (lack of very good cal kit) reference imposed limitations are on the equipment I own (in this case, the Agilent E7459a). Most importantly, measurements of one port insertion loss and one port return loss should be calibrated, but the equipment I have was probably calibrated against a very good cal kit (more then -40dB across the almost 3 GHz spectrum) and I would like to get a sense of how far off this the instrument is, in its current state (last cal was 2011 due for re-cal in 2013). All of this in addition to using such devices for measurements. I only paid $275 for the E7495a, and I certainly can not afford anything near the cal kit that would have been included which would probably cost $1000 or more now. |
| Mechatrommer:
--- Quote from: hendorog on February 22, 2018, 06:41:15 am --- --- Quote from: Mechatrommer on February 22, 2018, 05:28:57 am ---fwiw, among other things, attached is attenuator plot provided from Kirkby to me. the result i got on my VNA is much noisier... --- End quote --- He has reduced the IF bandwidth from the default. That would reduce the noise. What VNA have you got? --- End quote --- Deepace KC901V. i'm start to think its a toyish VNA, but i'm not done testing yet. |
| G0HZU:
--- Quote ---fwiw, among other things, attached is attenuator plot provided from Kirkby to me. the result i got on my VNA is much noisier, so i know something went wrong. i'm ordering stuffs to further verify my VNA condition if its fits for measurement etc later. i hope they will not get lost during CNY... --- End quote --- Is that attenuator (reference) plot taken with the 8720D VNA and your cal kit? Or is it a 'best' reference taken of the attenuator with the 8720 and a Keysight/Agilent cal kit? See the text below from the Kirkby website. --- Quote ---The Kirkby Microwave 7 GHz 85033 SMA calibration and verification kit is by far the most popular kit we sell. It can be used to calibrate virtually any network analyzer to enable SMA, 3.5 mm or 2.92 mm coaxial devices to be measured, irrespective of the test ports on the VNA (N, 3.5 mm, APC7, 2.4 mm etc). The connectors on the calibration kit should match the device under test (DUT) and not necessarily the connectors on the VNA. The frequency range of the SMA coaxial calibration kit is from DC to 7 GHz, although higher frequency versions can be built to order. The kit is both a calibration and verification kit, since it supplied with an attenuator which has been measured on an HP 8720D (20 GHz) VNA using a Agilent 85052B 26.5 GHz 3.5 mm calibration kit. Therefore after setting up the calibration kit, calibrating the VNA, the user can check the VNA is performing properly by measuring the attenuator which is supplied, and comparing that to the measured results, which are on a USB stick supplied with the kit. --- End quote --- If a calibration kit is made using SMA F-F bullets and end caps there are a few things that will limit its performance. There will be some (extremely tiny) added inductance at the end of the SHORT and also the SMA bullet won't have a perfect 50R Zo. The SMA bullet is about 42ps in terms of delay and this is longer than a regular 85033 cal kit and so this can make any phase variation (due to imperfect 50R Zo) appear slightly worse. The 85033 cal kit uses precision 3.5mm connectors and an air dielectric and it is much better suited for use up at 7GHz. It doesn't take much to get 4 degrees of phase error over 6GHz in a DIY cal kit. If you get several degrees of phase error and it isn't corrected for by the cal kit corrections then you can expect to see that reference plot degrade a lot by 5GHz and it will get quite noisy by 7GHz. Also, an inline test of a 3dB attenuator isn't a very critical test. I can show you what my old DIY cal kit can do to 7GHz but I'll have to generate a polynomial to correct the SHORT. Otherwise it will only be good to about 3GHz. I'll have a go at changing my simulation/model to produce L0, L1, L2, L3 correction factors for my old cal kit. It should then do quite well in an attenuator test. However, I see this process as polishing a turd once you get up to 7GHz. Much better to have a decent 85033 cal kit here. |
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