[sdiy] BBD question

[Tom Wiltshire]

On 30 Aug 2008, at 04:48, Ian Smith wrote:

>
>
>>> I've got the old Panasonic BBD manual and it shows one with a 20  
>>> kHz 12dB lowpass filter at both the input and output... I'm  
>>> guessing that's to reduce clock noise. So I'm thinking have a  
>>> filter at the beginning of the chain and between each BBD and one  
>>> at the end.
>>>
>>
>> The one at the input is probably considered an anti-aliasing  
>> filter, and
>> at the output a reconstruction filter (reduces clock noise). In that
>> case a filter between BBD stages is probably a good idea to prevent
>> aliasing in the second BBD.
>
> Cool! I feel all smart and stuff!
> Now, if I wanted to tap the chain of BBDs, would I tap after the  
> filter between BBDs?

Yeah, that'd do it.
The problem is noise. By the time you're to your four or fifth tap,  
you're not going to hear much signal underneath the waterfall.

Regards
Tom