[time-nuts] wtd: WWVB info

Jim Lux jimlux at earthlink.net
Fri Aug 7 19:02:56 EDT 2015

On 8/7/15 1:40 AM, Hal Murray wrote:
> kb8tq at n1k.org said:
>> Well, at least *some* of the chips out there do not make it to 96 KHz when
>> sampling at 192 KHz. It’s  been a few years since I dug into them. Back then
>> a chip that had an internal filter that went to 96K was very much the
>> exception rather than the rule. If the only point of 192K is getting to a
>> 96K bandwidth, a lot of the chip guys missed out on it ….
> Where did 192 KHz come from?  Why is anybody interested in anything that far
> over 2*44 KHz?

There's lots of high resolution parts at that rate..
And if it's that fast, odds are the built in sample/track/hold is good 
enough that you could directly sample the 60kHz without much trouble.

With a slower ADC and a good analog BPF and a good sample/hold, you 
could sample at a few kHz, but that shifts the design burden to the BPF 
and the sample/hold.

> It's common to have an audio ADC run much faster than Nyquist, but that's a
> hack to make it easier to build the cut off filter.  You build a simple
> analog filter and a sharp digital filter and decimator so the output is 2x
> the target frequency.  You get what you want without a fancy analog filter.
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

More information about the time-nuts mailing list