[hpsdr] Horton (or other) gain distribution targets?

[Ray Anderson]

>Hi Jim,

>The ENOB of the AK ADC on the Janus board is 20. Given the max input of
>1.5v p-p you can work out the MDS and hence the  gain required on each
>band.

>Gain will be required in the ISD but we may not need a preamp on
10/12m, we 
>will require one on 6m and above. 

>73's Phil...VK6APH 


Phil, can you go into a bit more detail on the AK ADC ENOB number?

Since ENOB = (SINAD-1.76dB)/6.02 , we can say the SINAD =
(6.02*ENOB)+1.76dB

So for a ENOB of 20 then SINAD = 122.16 dB . So far, so good. 

Now looking at the AK5394a datasheet we find S/(N+D) in the 87dB to
110dB range (depending on the sampling freq and input level). Is S/(N+D)
the same as SINAD ?

I find a S/N (a-weighted) spec of 123dB typ or 117dB min, but this isn't
the same as SINAD. (or is it ??)

Could you elaborate a bit on the interpretation of the AK5394a specs?
Thanks!


One other related question. I notice in the calculation write-up on the
Mercury Wiki page you talk about a IP3 for the ADC chip. Can you really
talk about IP3 for a ADC since it doesn't gracefully compress when
overloaded but acts as a hard limiter? Thanks again...

73 de Ray	WB6TPU




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