[hpsdr] Sampling

[James Courtier-Dutton]

FRANCIS CARCIA wrote:
> ***** High Performance Software Defined Radio Discussion List *****
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> 
> I run 75 KHz sampling on my PDM rig so the integrating filter set at 8 KHz gives me about 70 dB of attenuation of the sample frequency. I follow the filter thing because I would have a large filter if my sample was 24 KHz.
>   It is the gear head in me to always wonder the limits of a new idea like this cool stuff.
>   I still feel the best system will have the bandwidth limited at the input but feel free to prove me wrong. frank
> 

If you read some of the specs of Audio ADCs, you will see that even when
capturing at 48KHz, the ADC chip is probably capturing at 192KHz or
above, using a simple front end filter, normally 0.45 of sampling
frequency, and then internally doing digital filtering down to 48Khz,
then simply dropping the unneeded samples.

James



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