Products > Test Equipment
Best VNA for around or under $2000?
mark432:
Does LiteVNA64 actually allow you to define cal standards?
From looking at the manual it seems that it just assumes the SOLT are perfect devices.
This seems a bit bonkers to me for something that is going up to 6 GHz.
I doubt that the short and open standards they provide line up perfectly with the reference plane. You would think you could at least set the parameters of the thru.
But the even bigger point is cables/adapters. Sometimes you need to measure things at the other end of cables and adapters.
I have a regular nanoVNA, and I didn't worry much about it because of lower frequency limit.
I suppose you just have to measure a reference standard and then correct your data after the fact.
Still, I wonder what the phase error after calibration is.
Regarding the LibreVNA. I see that an electronic calibration module is hitting the market. I wonder why they made it a 4 port cal module, when the only librevnas I can find are 2 port?
Is there a 4 port model in the works? I doubt it, but I would love a dual-source 4 port LibreVNA.
knudch:
You can do 4 port by using 2 LibreVNA
Supported in SW, called compound device
As understand it, 4 port can be done with 2 of shelf LibreVNA
8 if you some additional PCB's
But you will not have phase information between each unit...as I understand it
Have never tried it as I don't have 2 LibreVNA's
There also something called Mixed Mode....please read the support mail list or ask the designer
Knud
joeqsmith:
--- Quote from: mark432 on December 07, 2024, 06:47:30 am ---Does LiteVNA64 actually allow you to define cal standards?
--- End quote ---
Going thought the menus of a fairly recent version of firmware, it does not appear to.
--- Quote from: mark432 on December 07, 2024, 06:47:30 am ---From looking at the manual it seems that it just assumes the SOLT are perfect devices.
This seems a bit bonkers to me for something that is going up to 6 GHz.
--- End quote ---
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...).
--- Quote from: mark432 on December 07, 2024, 06:47:30 am ---I doubt that the short and open standards they provide line up perfectly with the reference plane. You would think you could at least set the parameters of the thru.
But the even bigger point is cables/adapters. Sometimes you need to measure things at the other end of cables and adapters.
--- End quote ---
Bigger point? Normally I would cal these out. I normally have cables attached and measure on the other end.
--- Quote from: mark432 on December 07, 2024, 06:47:30 am ---I have a regular nanoVNA, and I didn't worry much about it because of lower frequency limit.
I suppose you just have to measure a reference standard and then correct your data after the fact.
Still, I wonder what the phase error after calibration is.
--- End quote ---
Like how the LibreVNA requires a PC, if you want to perform more advanced math with the LiteVNA, you also would need a PC.
***
Same for any of these low cost VNAs, not just the LiteVNA.
***
Link showing LiteVNA HW rev 3.2 + PC + Solver to perform T-Check (after sorting out a few problems). The only way to get that level of performance was to characterize the cheap standards and enter that data into Solver. The LiteVNA is the limiting factor, not the standards.
https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/msg5685217/#msg5685217
Someone had attempted a similar test using the LibreVNA and I think they achieved 3GHz. Similar the the 4GHz I saw with the LiteVNA.
joeqsmith:
I put together some quick software to try out that old Weinschel 63dB step attenuator and all of the stages are fine.
Using an IFBW of 500Hz, I stepped from 0 to 60dB, then inserted that 40dB fixed attenuator.
joeqsmith:
Showing 80, 90 & 100dB with 4kHz IFBW and 1000 averages.
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