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Kirkby calibration kit alternatives?
Andrey_irk:
G0HZU,
Ah, now I see what you mean.
--- Quote from: G0HZU on July 30, 2018, 03:42:48 pm ---I guess so but I don't know if a VNA would interpret this as a 51.1R resistor with a 50R Zo delay or as a 51.1R resistor with a 51.1R delay.
--- End quote ---
I think if you leave the load connected after calibration and take a look at the smith chart you'll see how it interprets the 51.1R load. Anyway, in E5071? for instance? you can set offet Zo, impedance value and even offset loss. Although if you want to specify load impedance that is not 50R, then it will be a different standard - arbitary impedance. And I don't know if there are any limitations with using this kind of standards instead of usual loads.
Andrey_irk:
Still, I understand that it is not difficult to measure LF impedance, but I don't know if it'll give a real benefit. Maybe Dr. Kirkby calculated all the errors and realized that it really doesn't worth it (to some extend of course). Maybe the noise floor is much higher.
mark03:
--- Quote from: Bud on July 30, 2018, 03:30:42 pm ---Can't you enter the reference impedance value in the VNA settings and call it a day. Not all VNAs may have that setting changeable though.
--- End quote ---
Yes, at least on my VNA (Agilent 4396B) the "arbitrary impedance" standard type has the usual offset parameters (delay, loss, Z0), then a separate termination impedance.
I found this necessary to accurately model my own DIY set of female SMA standards. The professional cal kit I borrowed (a Copper Mountain S911) is spec'ed at better than 38 dB return loss from DC to 9 GHz. The [measured by me] DC resistance is 50.8 ohms, which is still in spec, but makes LF measurements less accurate than they ought to be. I couldn't figure out why my DIY load was measuring at ~ 49.2 ohms on the VNA, all the way down to 1 MHz, when I had measured its DC resistance at 50.0 ohms on my DMM :-DD
I guess the moral of the story is that some cal kits (not just Kirkby) are really focused on microwave performance where 40 dB return loss is pretty good, and it's mostly weirdos like ham-radio people who care about LF accuracy, so if you are one of those people it's worth measuring the DC resistance and using that up to ~100 (?) MHz. Unless you have access to higher-end kits like G0HZU ;)
Noy:
Hi, is the suggested :
https://www.sdr-kits.net/index.php?route=product/product&path=66_68_69&product_id=50
Kit useable for up to 3.2GHz im thinking abaout buying / hacking a SSA3021X-Plus but additional >>100€ for a calkit is said, the SSA is expensive enough for me..?
Noy:
SSA3021X-Plus is hackable up to SVA1032X
Than it is a VNA.
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