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Sub $1000 VNA for antenna matching
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joeqsmith:
The LiteVNA is so much slower than my original NanoVNA.  Of course, with the Lite you can sweep very fast if you don't care about the data.  So when I suggest slower, I'm setting the IF to something reasonable to get comparable noise with the NanoVNA.  I have tried a few experiments to improve the Lite's noise but so far, my original Nano is lower. 

I don't own a LibreVNA and don't know too much about it.  I suggest joining their group and asking the designers any questions you have. 


--- Quote ---Is it a common drawback of LibreVNA & others (except the nano) to struggle to do clean measurements over the low-end frequencies ?
--- End quote ---

CMT offers a VNA that would fit my use very well but was more than I wanted to spend for my hobby.   When I was looking at replacing my 70's VNA with something newer,  I had asked in the HP group about lower frequency use (see below) and suspect it's not a common use case.


--- Quote ---Does one really need such sophisticated instrumentation to work
below 1MHz?  50 ohm transmission lines scarcely even exist at such low frequencies.

The VNA was built to make it possible to characterize components so that you could more easily build circuitry by stringing together such characterized components, lumped along transmission lines.

They are necessary in the microwave region, where there is really nothing that even resembles a pure resistance, pure capacitance, or pure inductance.

At low frequencies, you can very much rely on your parts being what you think they are.  Capacitors are capacitors, and not a mixture of capacitance, inductance, and resistance.

Unless physics has changed, I don't see a VNA being necessary, or even useful at such low frequencies.

-Chuck Harris


Joe Smith via Groups.Io wrote:

     Does one really need such sophisticated instrumentation to work below 1MHz?

I appreciate your concern.  I would say in my particular case, placing the question mark after "instrumentation" is appropriate and the answer to which is no.   I certainly have no need for any of my equipment.  It's a hobby and I enjoy it.


Chuck Harris
1/16/20   #101895  

True, but wanting your Microwave VNA to go down to DC is like wanting your Ferrari to have tank tracks.

It just isn't right.  Better would be to have a Ferrari and a tank.  They serve different functions.

-Chuck Harris

--- End quote ---
joeqsmith:
Don't laugh too hard.  Attached photo showing my attempt to tap into the matching network on the BLE board.  This is a semi rigid silver plated copper coax with an OD of 2.2mm (0.086).   Much too fat for this application.   

Link to antenna data sheet.
https://www.yageo.com/upload/media/product/productsearch/datasheet/wireless/An_Ceramiz_2450_3216_L00_0.pdf
mawyatt:
Looks like you did an OK job, what's readily available with OD less than 2.2mm?

Best,
Mechatrommer:

--- Quote from: mawyatt on November 29, 2022, 12:07:42 am ---Looks like you did an OK job, what's readily available with OD less than 2.2mm?

--- End quote ---
coax 1.13mm.. china come.. the problem is... did the coax deembedded? or proper way/calibration made right on the coax's tip? and then there's parasitics from input tracks that might differ from actual operation (when input driver/ic populated) ::)
joeqsmith:

--- Quote from: Mechatrommer on November 29, 2022, 12:15:44 am ---
--- Quote from: mawyatt on November 29, 2022, 12:07:42 am ---Looks like you did an OK job, what's readily available with OD less than 2.2mm?

--- End quote ---
coax 1.13mm.. china come.. the problem is... did the coax deembedded? or proper way/calibration made right on the coax's tip? and then there's parasitics from input tracks that might differ from actual operation (when input driver/ic populated) ::)

--- End quote ---

The UT-047 MICRO-COAX I had linked above is 0.047".   For calibration, I had made two probes which I had phase matched.  The one was shown in the previous picture.  The other has a sewing needled attached to the shield.  This probe is used to cal the system attaching it to a section of copper PCB and in my case, just leaving it open.  Again, the ideal model was used.  A better solution would be to toss some major cash into it but it was just for fun.  The radio must be placed onto the circuit board.  I had just hand cut a ground plane and soldered to that.    One other problem was because the coax is so thick I was not able to install the shield.  All these details add up.

It's one thing to have datasheets for a single component.  In this case, I have no way to verify my results. 

I set it all up with the LiteVNA. 
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