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Sub $1000 VNA for antenna matching

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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:

--- Quote from: Mechatrommer on November 26, 2022, 08:42:38 pm ---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.

--- End quote ---
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:

--- Quote from: joeqsmith on December 06, 2022, 01:36:33 pm ---
--- Quote from: Mechatrommer on November 26, 2022, 08:42:38 pm ---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.

--- End quote ---
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

--- End quote ---
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.

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