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| Kirkby calibration kit alternatives? |
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| tautech:
--- Quote from: Noy on November 18, 2020, 10:35:57 pm ---Is it worth to pay the "extra" for the SDR Kits Calkit (box, load measurment, male male Adapter) instead of buying the parts as "single" from Mouser? Refering to: http://www.hhft.de/index.php?page=competences&subpage=calibration Mouser: 56€ + 16% vat inkl. shipping SDR Kit : 75€ inkl. Vat + shipping (85€ total) I think same parts and i think the only measured thing from SDR kits is resistive load resistor.. I can do this also with 4 wire measurment with my fluke8840a or? Or are there more measurment done by them? Male - male Adapter is sure also available from Mouser (didnt searched , not sure if i need this one...) Suggestions?? --- End quote --- SOL are the minimum you need and some kits also come with a through but they are all rated to a max frequency and when swept to that frequency there must be little change across the full range. You can sorta cobble a set together but good results are tricky to achieve as I found out trying to make some on the cheap for myself. :( In the end I sucked it up and bought a $400 SMA Cal kit. :scared: |
| Mechatrommer:
--- Quote from: Noy on November 18, 2020, 10:35:57 pm ---Is it worth to pay the "extra" for the SDR Kits Calkit (box, load measurment, male male Adapter) instead of buying the parts as "single" from Mouser? Refering to:http://www.hhft.de/index.php?page=competences&subpage=calibration --- End quote --- well without providing CAL kit coefficients or s1p profiles, there is not such thing as even "Kirkby alternative", you can buy whatever cal kit you want and be happy about it, you can even make your own its doesnt matter. you can do the "inverse" or "reverse" profiling from whatever s1p/s2p plot from your VNA. if you care about Load quality that we all can measure with any DMM, you can get from already mentioned brand such as Rosenberger or whatever name they are you can browse the thread. or better, buy few Loads and hand pick which one is the closest to absolute "Fifty Ohms" and still cheaper compared to any knock off or "Kirkby alternative" buzzed/advertised as "CAL kit" out there (you can already have few terminations to test things such as 2/3/4/5 50 ohm signal splitter etc you are going to need it today or 10 years from now). you may get cheaper than your mentioned Mouser or SDR-kit's CAL kit at $50 and get a free (NanoVNA V2+ with decent quality 50ohm Zo SMA pigtail cables) if you buy from Tindie... or $4 this just look closely from the link you gave about these facts... --- Quote ---Match / Load (female): Offset Length: 0 mm C-coefficients: all = 0 F / Hz L-coefficients: all = 0 H / Hz Short (female): C-Coefficients: all = 0 F / Hz L-Coefficients: all = 0 H / Hz Open (female): C-Coefficients: all = 0 F / Hz L-Coefficients: all = 0 H / Hz Thru (female / female): Offset Length: 0 mm (The reference plane lies in the middle of the thru-connection) --- End quote --- this is what we call... Ideal Calibration Standard, even HP $20K CAL kit cant achieve this in reality. offset length can be measured physically with caliper, one eye closed and tongue at the right angle. electrical one way trip can be observed from VNA plot/TDR and punch the figure into the formula to get dielectric constant and hence "electrical length" aka "offset length". the deal here is to get 3rd degree polynomial approximation for those Cn and Ln up to whatever BW you are interested in, maybe those are negligible up to say 3-6GHz? i dont know. if someone can figure that out from "reverse" characterization from even a cheap VNA like NanoVNA alone, there is no reason to buy from Kirkby or HP at all, they should not be even mentioned in the first place, and there should not be any comparison to or no such thing as "Kirkby alternative" at all... $4 CAL kit is what we should look after if we dont care about polynomials, ymmv. cheers. |
| Noy:
There are more informations available: https://www.sdr-kits.net/documents/Rosenberger_Female_Cal_Standards_rev5.pdf So because they are "standard" Rosenberger types i think these informations are also true for the "single buy" mouser parts. SDR-Kits are using the same parts like stated on the website. But I#m unsure if SDR-Kits are measuring anything "more" than the 50 Ohm impedance and write this value on top of the box... If this is all there is no need to pay the "extra" if its only a small wood box... This is what i mean. I think rosenberger parts are way more "true" even with this provided sheet against these cheap china parts (i already have delock 12GHz N->SMA Adapters, some decent SS405 2x (20cm) / 2x RG405 (1m) and some (10x 20cm / 2x 1m) RG316 cables for up to 3.2GHz (hopefully) also RG58 with bnc but these are <<1GHz useabel..) And all kind of "cheaper" SMA adaptors. Only a calkit with "stated true" things is missing (beside the china stuff) but 400$ if the whole VNA was only 1600€ is for hobby use a bit too much. So the rosenberger parts are (i think for hobby use) best bang/buck? And since i will not go higher than the 3.2GHz i think its sufficiant? But I'm new to this stuff so i will need an advice. |
| tautech:
--- Quote from: Noy on November 19, 2020, 08:04:20 am ---There are more informations available: https://www.sdr-kits.net/documents/Rosenberger_Female_Cal_Standards_rev5.pdf So because they are "standard" Rosenberger types i think these informations are also true for the "single buy" mouser parts. SDR-Kits are using the same parts like stated on the website. But I#m unsure if SDR-Kits are measuring anything "more" than the 50 Ohm impedance and write this value on top of the box... If this is all there is no need to pay the "extra" if its only a small wood box... This is what i mean. I think rosenberger parts are way more "true" even with this provided sheet against these cheap china parts (i already have delock 12GHz N->SMA Adapters, some decent SS405 2x (20cm) / 2x RG405 (1m) and some (10x 20cm / 2x 1m) RG316 cables for up to 3.2GHz (hopefully) also RG58 with bnc but these are <<1GHz useabel..) And all kind of "cheaper" SMA adaptors. Only a calkit with "stated true" things is missing (beside the china stuff) but 400$ if the whole VNA was only 1600€ is for hobby use a bit too much. So the rosenberger parts are (i think for hobby use) best bang/buck? And since i will not go higher than the 3.2GHz i think its sufficiant? But I'm new to this stuff so i will need an advice. --- End quote --- See what they're really like when you sweep them. I played around with a SMA load member hendorog gave me which he said measured quite reasonable with his HPAK and SH VNA's and it was pretty good on my SVA1032X however his Kirkby Cal kit was somewhat better. IIRC I've posted some sweeps in the SVA thread, go have a peep. |
| Mechatrommer:
afaik, they can only gather research on nice appearance "butt plug" for open or short etc and save your time from calculating offset (mean) length and collect/put them in a nice wooden box and possibly do the "comparative/relative" quality check to their more pricey CAL Std (you can ask them what, i dont know). those are worth the price increase if you can appreciate that. but the cost for characterization is another thing. individual/unique coefficients/character profile files for your kit and getting a nice calibrated equipments (aka expensive) to get a reasonable transferable standard worth that another cost. --- Quote from: tautech on November 19, 2020, 08:14:00 am --- --- Quote from: Noy on November 19, 2020, 08:04:20 am ---But I'm new to this stuff so i will need an advice. --- End quote --- See what they're really like when you sweep them. --- End quote --- compared to what? i can make a sloppy diy cal kit and make them flat to 6GHz on a VNA with zero offset everythings. one clue though to see a good LOAD without relative comparison is its return loss, but its real impedance and esp for OPEN and SHORT... you can be happy about anything. |
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