[hpsdr] [FlexRadioSmartSDR] Optimum ADC loading.

[Lester Veenstra]

  Rob,

"Another issue is what is the distortion vs. band noise."  Actually not
another issue.  What you have termed "band noise",  is what I was calling
The noise floor of the Preamp/ Antenna noise from the ADC terminated in the
antenna feed should be about 15 dB above  the internal noise.

 

"If Intermod is below band noise, it doesn't matter."    It (intermod) does
not matter as long as it is 15 dB below "band noise" or the antenna noise
floor.  But your point is correct. As long as the Percent Time in Clip
(PTIC) is below 1e-06, ADC generated intermod will not matter   

 

"Of course band noise is all over the map depending on which band, time of
day and direction a directional antenna is pointed."   This is a reason why
it is a good idea to run a daemon keeping the PTIC in the 1e-07 to 1e-06
range.  This should (IMHO), subject to experimental verification, also keep
the received noise floor above the ADC noise floor by the 15 dB target.
This is a seat of the pants approximation. I cannot promise where my pants
have been, Verify, do not trust!

 

Les

 

 

Lester B Veenstra  MØYCM K1YCM W8YCM

lester at veenstras.com

 

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