Sub $1000 VNA for antenna matching

[joeqsmith]

I've mounted the radio to a sectioned board with the proper layout.  Attached photo shows my hack job on the shield.  I found a bit of Arlon (not sure the part number) and epoxied the sectioned board with radio to it.  This will allow easy mounting to the rotor's mast.   Once this dries, I will repeat the calibration and measurements with the LiteVNA.   

[joeqsmith]

I've attached a photo showing the setup.  Note that the shield was soldered to the coax.   

Looking at the return loss, the Red trace was just after calibrating the VNA.  The Yellow trace is using yesterdays calibration.  There's a bit of difference which I'm not too surprised.  This time I was using some copper foil tape rather than the PCB.    The bigger change was due to all the other changes in the setup. 

The 2D plot would be how I would normally use the radio.   

[joeqsmith]

please follow this post... https://www.eevblog.com/forum/rf-microwave/clone-85033e-vna-cal-kit-measured-against-pico-cal-kit-using-librevna/msg4475422/#msg4475422 i have yet to get a good answer on why the ringy plot of LibreVNA output file. the last time we were discussing among VNA users that the ringy plot is due to internal mismatch (tracks are not 50 ohm impedance)... the way i see it, its internal problem and difficult to cancel from external tricks, unless the designer takes care of this internally or in FW. ymmv.

I was reading the LibreVNA group yesterday and it seems they have new hardware.  Someone posted an AB compare that may be of interest.  

https://groups.io/g/LibreVNA-support/topic/what_is_the_spec_defrance/95474170?p=,,,20,0,0,0::recentpostdate/sticky,,,20,2,0,95474170,previd%3D9223372036854775807,nextid%3D1666293968019920350&previd=9223372036854775807&nextid=1666293968019920350

[Mechatrommer]

please follow this post... https://www.eevblog.com/forum/rf-microwave/clone-85033e-vna-cal-kit-measured-against-pico-cal-kit-using-librevna/msg4475422/#msg4475422 i have yet to get a good answer on why the ringy plot of LibreVNA output file. the last time we were discussing among VNA users that the ringy plot is due to internal mismatch (tracks are not 50 ohm impedance)... the way i see it, its internal problem and difficult to cancel from external tricks, unless the designer takes care of this internally or in FW. ymmv.

I was reading the LibreVNA group yesterday and it seems they have new hardware.  Someone posted an AB compare that may be of interest. 

https://groups.io/g/LibreVNA-support/topic/what_is_the_spec_defrance/95474170?p=,,,20,0,0,0::recentpostdate/sticky,,,20,2,0,95474170,previd%3D9223372036854775807,nextid%3D1666293968019920350&previd=9223372036854775807&nextid=1666293968019920350

still look ringing to me on both plot, is that a Through test? not really clear..

[joeqsmith]

Agree, not at all what I would expect.  With the other posts showing difference in cal standards causing it, compared with what I show using various loads, I wonder if it's a user problem.  Maybe a problem with their math.  

They really should have sent one to someone that knew what a VNA was.

[Smokey]

...
FYI on the Lite.
The first one I bought worked well and met the suppliers specs.  A friends had very high noise.  They bought a second and shipped me theirs.  Their second one also had high noise.  After some testing, I found the Lite was very sensitive to the input voltage level from the USB port.  Basically, to get around it, I made a USB cable with a diode in series with the power to lower it.  This solved the problem.   
...

I'm looking at getting one of these LiteVNAs.  What should I be looking at, performance wise, to determine if a unit has an issue with the USB voltage? 

[joeqsmith]

...
FYI on the Lite.
The first one I bought worked well and met the suppliers specs.  A friends had very high noise.  They bought a second and shipped me theirs.  Their second one also had high noise.  After some testing, I found the Lite was very sensitive to the input voltage level from the USB port.  Basically, to get around it, I made a USB cable with a diode in series with the power to lower it.  This solved the problem.   
...

I'm looking at getting one of these LiteVNAs.  What should I be looking at, performance wise, to determine if a unit has an issue with the USB voltage?

I've posted data showing the problem, how I collected it and also how to mitigate it.  Did you have a specific question about that?  I understand they released an update to the hardware to improve its performance.  Someone had asked how it compared with what I had shown.  There was no response from the designers and all went silent.  You can find that on the LiteVNA groups.io.   

[Smokey]

Cool.  Thanks for the info.  I think this is the forum post regarding the power supply update:
https://groups.io/g/liteVNA/topic/the_new_litevna64_which/93138117

The last messages are from 11/11/22 and claim the distributors like randl.com have the 64.0.3.1 version.

[joeqsmith]

Yes, that is the thread.   Looks like it grew a bit. 

If you buy one, I would be interested in having you run a simple test just to get some idea how much they improved it compared with my stock one. 

[Smokey]

Yes, that is the thread.   Looks like it grew a bit. 

If you buy one, I would be interested in having you run a simple test just to get some idea how much they improved it compared with my stock one.

It's on it's way.  I'll update when it gets here.

[Smokey]

LiteVNA64 from here:
https://store2.rlham.com/shop/catalog/product_info.php?products_id=75669

[Smokey]

Arrived.  Got the new "64-0.3.1" label style on the case (image from store site):



Firmware version it shipped with = v1.3.07
Build time = Aug 30 2022 - 10:14:02

[Smokey]

I feel like I'm missing something about firmware versions.

This looks like DiSlords's github, but there is no liteVNA repo: https://github.com/DiSlord

The liteVNA groups.io doesn't appear to have the wiki setup and I'm not seeing a firmware section: https://groups.io/g/liteVNA

There was a link to a google drive in one of the posts, but it's not clear what versions are on it, and all the files appear quite old: https://drive.google.com/drive/folders/10lU5xnwmHDnPX98z21ky09N8nb_cEOk4

There is a nanoVNA beta groups.io page, but it's invite only: https://groups.io/g/nanovna-beta-test

What am I missing?