Products > Test Equipment
Best VNA for around or under $2000?
mark432:
--- Quote from: joeqsmith on December 08, 2024, 12:04:48 am ---Well, it was designed for a certain price. I am not sure if the hardware has enough resources to support it (code space, processing power...).
--- End quote ---
It's not really a "horsepower" limitation as the calibration only needs to be calculated once when you are doing it.
You're solving for a matrix, that you're going to multiply by your measured data matrix, to give the actual result.
There's definitely more code involved in allowing definable cal sets, but it's all math that you only calculate once at cal.
( I wouldn't expect code space to be a problem these days.)
Once it's done, you're doing the same number of calculations every sweep regardless of the cal type.
--- Quote from: joeqsmith on December 08, 2024, 12:04:48 am ---Bigger point? Normally I would cal these out. I normally have cables attached and measure on the other end.
--- End quote ---
Yeah, but often at the other end of your cable you might have other sex or other gender connectors than the supplied cal standards.
Like when measuring at the end of a several foot SMA to N cable. Best case, you're using a decent adapter than only adds half an inch of phase shift and has a 30 dB RL.
Quite likely you're doing worse.
VNAs are about the best example of "garbage in, garbage out" for test equipment.
I don't see anything else better for the price, but I'm leaning towards LibreVNA if I ever want upgrade from my NanoVNA.
It seems to have much closer to a normal VNA functionality.
The NanoVNA reminds me more of something like an Anritsu Sitemaster than a full VNA.
I would think the best way to cover cal for super low cost VNAs would be to allow known s-parameter cal for the datasets.
The manufacturer can take 1 minute and measure the standards on a traceable VNA and then provide those files with the standards. No need to try and make them perfect SOLT. Just use decent repeatable connectors and stable resistors.
Many of us will have access to a lab-grade VNA and it would be easy to measure a handful of parts as home standards.
joeqsmith:
--- Quote from: mark432 on December 10, 2024, 01:10:15 am ---
--- Quote from: joeqsmith on December 08, 2024, 12:04:48 am ---Well, it was designed for a certain price. I am not sure if the hardware has enough resources to support it (code space, processing power...).
--- End quote ---
It's not really a "horsepower" limitation as the calibration only needs to be calculated once when you are doing it.
You're solving for a matrix, that you're going to multiply by your measured data matrix, to give the actual result.
There's definitely more code involved in allowing definable cal sets, but it's all math that you only calculate once at cal.
( I wouldn't expect code space to be a problem these days.)
Once it's done, you're doing the same number of calculations every sweep regardless of the cal type.
--- Quote from: joeqsmith on December 08, 2024, 12:04:48 am ---Bigger point? Normally I would cal these out. I normally have cables attached and measure on the other end.
--- End quote ---
Yeah, but often at the other end of your cable you might have other sex or other gender connectors than the supplied cal standards.
Like when measuring at the end of a several foot SMA to N cable. Best case, you're using a decent adapter than only adds half an inch of phase shift and has a 30 dB RL.
Quite likely you're doing worse.
VNAs are about the best example of "garbage in, garbage out" for test equipment.
I don't see anything else better for the price, but I'm leaning towards LibreVNA if I ever want upgrade from my NanoVNA.
It seems to have much closer to a normal VNA functionality.
The NanoVNA reminds me more of something like an Anritsu Sitemaster than a full VNA.
I would think the best way to cover cal for super low cost VNAs would be to allow known s-parameter cal for the datasets.
The manufacturer can take 1 minute and measure the standards on a traceable VNA and then provide those files with the standards. No need to try and make them perfect SOLT. Just use decent repeatable connectors and stable resistors.
Many of us will have access to a lab-grade VNA and it would be easy to measure a handful of parts as home standards.
--- End quote ---
The files I used for the T-Check experiment are 512kB, male only, and limited to 1601 points. LiteVNA support more points and we would expect to support both M/F. Trivial for the PC.
knudch:
--- Quote from: mark432 on December 10, 2024, 01:10:15 am ---
I would think the best way to cover cal for super low cost VNAs would be to allow known s-parameter cal for the datasets.
The manufacturer can take 1 minute and measure the standards on a traceable VNA and then provide those files with the standards. No need to try and make them perfect SOLT. Just use decent repeatable connectors and stable resistors.
Many of us will have access to a lab-grade VNA and it would be easy to measure a handful of parts as home standards.
--- End quote ---
There is a Guy Kurt Poulsen , search for him in the LibreVNA forum, he has written a article about "transfer" all CAL parametre from a lab-grade to home standards in the LibreVNA.
Knud
Miek:
The LiteVNA64 does allow you to define cal standards, it's under Calibrate -> Calibrate -> Calibration Standard. I checked on v1.3.31 and the latest v.1.3.36
joeqsmith:
--- Quote from: Miek on December 10, 2024, 12:27:31 pm ---The LiteVNA64 does allow you to define cal standards, it's under Calibrate -> Calibrate -> Calibration Standard. I checked on v1.3.31 and the latest v.1.3.36
--- End quote ---
Nice find. Mine is much older (07) and appears to at least have some limited settings. They do not allow a loss term for any of the standards. The only standard that allows you to define Z0 is the load. The load also allows an L & C term which at least METAS does not. It assumes everything is coaxial.
mark432 suggested ditching the polynomial for the database. My friends new H4 and the LiteVNA do have that card reader which would easily hold what ever files I would come up with. May be an option if there was a need for it.
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