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cal isolation

tekguy la All Messages By This Member #31461 Hi,what do i do during the cal when it gets too the isolation?,ive seen a few vids but its not clear,do i connect the 50 ohm load to ch 0 or leave nothing connected to that port,or put the load on ch 1 ,its not clear what i need to do.
John Gord All Messages By This Member #31463 tekguy, You should connect 50 ohm loads to both connectors. If you have an attenuator of 10 dB or more, that can be used as a reasonable 50 ohm load. --John Gord toggle quoted message Show quoted text On Sat, Feb 18, 2023 at 12:43 PM, tekguy la wrote: Hi,what do i do during the cal when it gets too the isolation?,ive seen a few vids but its not clear,do i connect the 50 ohm load to ch 0 or leave nothing connected to that port,or put the load on ch 1 ,its not clear what i need to do.
W0LEV All Messages By This Member #31464 Many times, it's appropriate to skip the isolation cal. Even professionally, HP (the 8753C) gives one the choice to specifically skip isolation. If you do conduct the isolation cal, terminate both ports with a good 50-Ohm load. Dave - W?LEV toggle quoted message Show quoted text On Sat, Feb 18, 2023 at 8:43 PM tekguy la <uktekguy@...> wrote: Hi,what do i do during the cal when it gets too the isolation?,ive seen a few vids but its not clear,do i connect the 50 ohm load to ch 0 or leave nothing connected to that port,or put the load on ch 1 ,its not clear what i need to do. -- Dave - W?LEV -- Dave - W?LEV
tekguy la All Messages By This Member #31465 does that mean i just leave both ports open and skip to the next step?.
W0LEV All Messages By This Member #31466 Yes, just declare the cal complete without doing the isolation. Dave - W?LEV toggle quoted message Show quoted text On Sat, Feb 18, 2023 at 10:28 PM tekguy la <uktekguy@...> wrote: does that mean i just leave both ports open and skip to the next step?. -- Dave - W?LEV -- Dave - W?LEV
John Gord All Messages By This Member #31467 On professional VNAs like the 8753, the internal isolation of the hardware is so good that the isolation calibration step is only useful if you are using a fixture that has isolation problems. For the NanoVNAs (of all flavors, I think), the internal isolation is not so great, and the added calibration step can help improve the dynamic range of S21. --John Gord toggle quoted message Show quoted text On Sat, Feb 18, 2023 at 02:19 PM, W0LEV wrote: Many times, it's appropriate to skip the isolation cal. Even professionally, HP (the 8753C) gives one the choice to specifically skip isolation. If you do conduct the isolation cal, terminate both ports with a good 50-Ohm load. Dave - W?LEV On Sat, Feb 18, 2023 at 8:43 PM tekguy la <uktekguy@...> wrote: Hi,what do i do during the cal when it gets too the isolation?,ive seen a few vids but its not clear,do i connect the 50 ohm load to ch 0 or leave nothing connected to that port,or put the load on ch 1 ,its not clear what i need to do. -- Dave - W?LEV -- Dave - W?LEV
Donald S Brant Jr All Messages By This Member #31468 On Sun, Feb 19, 2023 at 02:27 AM, John Gord wrote: the added calibration step can help improve the dynamic range of S21. Which is of little consequence unless you are measuring high-isolation devices like filters or diplexers, and none at all for those doing one-port reflection measurements (antennas), which I suspect is quite common. On my commercial VNAs I choose "Omit Isolation" unless it is specifically needed for the measurement at hand. 73, Don N2VGU

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