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NanoVNA Custom Software

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joeqsmith:
I tried a some short cables made from RG223 and noted little difference above 8GHz.   Its a bit too stiff. 
https://www.pasternack.com/flexible-0.216-rg223-50-ohm-coax-cable-pvc-jacket-rg223-u-p.aspx

You may have seen me use this cable as well.  It's much more flexible than the other double shielded cable I had been using.  Using this cable with all the adapters shown and careful calibratio, the cheap 20dB attenuator is still within a half dB sweeping from 1MHz to 6GHz.   Once we get into the harmonic mode, things fall apart but still useful.   

https://www.pasternack.com/flexible-0.122-rg188-ds-50-ohm-coax-cable-ptfe-jacket-rg188-ds-p.aspx

*** Note the two short RG223 cables to left

*** Letting the Lite run for a bit with the attenuator, seems stable. 

DiSlord:
The mode of operation on harmonics is not the standard mode of Lite, the 3rd and 5th harmonics are used for measurement, because of which the dynamic range suffers (this mode just optional, but can be useful for example in TDR measures  for get better resolution). It is better to calibrate at these frequencies at high AVG values, this will reduce the noise in the calibration data, as well as in the measured data).
In general, you can get ~ 50dB in these modes, but there is a very long calibration
My 40 and 50dB measures

Alextsu:
Hi, Joe,
Do You use a SMA fixed-torque wrench to attach the cables & DUTs every time or fix them by hand?

Mechatrommer:

--- Quote from: DiSlord on January 22, 2022, 05:42:46 am ---The mode of operation on harmonics is not the standard mode of Lite, the 3rd and 5th harmonics are used for measurement, because of which the dynamic range suffers (this mode just optional, but can be useful for example in TDR measures  for get better resolution).

--- End quote ---
:-+ if i buy a tool expecting to behave as in spec, and then the seller offers me a broken toy as a gift, i will happily accept that. i bought LiteVNA because 6.3GHz, now you offer 9GHz i will gladly accept that as bonus however broken it is. some application i can use eyeball or PC regression/averaging app to predict dut's behavior beyond 6.3GHz.. if you hear complaint from mourners you can ignore them. if they dont want the gift, they can always set stimulus to maximum of 6.3GHz.. btw i just asked Zeenko Store to ask Hugen to upgrade again NanoVNA-QT to support 9-10GHz, i hope they will listen.

joeqsmith:

--- Quote from: Alextsu on January 22, 2022, 05:53:27 am ---Hi, Joe,
Do You use a SMA fixed-torque wrench to attach the cables & DUTs every time or fix them by hand?

--- End quote ---

Normally, I try to leave the cables attaches to avoid wear.  For the Lite, I did install a couple of extensions to try and further minimize the wear.   

https://www.digikey.com/en/products/detail/amphenol-rf/132171RP/1011924

The adapters and cables are all torqued properly.   As for torquing  the DUT and cal standards, it depends.     Notice the cables I show that I claim are bad.  If you were using them below a few hundred MHz, you may find you get very good results with them.  Again, the lower the frequency, the less critical the mechanics which includes proper torque.  So to answer your question, it depends on what I am doing.  Just like calibration, a lot of times I won't do it or it's about the last thing I do.  Again, depends what I am after.

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