[time-nuts] NTP IRIG config help

[Jim Kusznir]

Thanks for the info!

I was adjusting the levels with alsamixer, which I suspect is a
digital mixer.  I hadn't thought of the potential issues there.

I was using the onboard sound, but I also have a "higher quality"
Soundblaster sound card.  Do some of these vary in quality so much as
to be unable to decode IRIG at all?

I think I will deploy PPS; I'd also like to deploy something to set my
time myself (IRIG sounds good), but I realize its not required.  I
haven't taken time to find all the connector-pieces to make the
required custom cable yet to do PPS; I had the parts on my shelf to
dump IRIG into my Line In on the sound card.

A related question:  for my IRIG out, should I directly dump that into
the sound card, use one BNC-T with a terminator, or two BNC-T's with
terminators, and pull the connection there?  Does it matter?

Thanks!
--Jim

On Mon, Mar 7, 2011 at 11:36 AM, Chris Albertson
<albertson.chris at gmail.com> wrote:
> There is an NTP email list.   questions at lists.ntp.org
>
> But really, all you need is the 1PPS output and some pool servers.
> If you have PPS working then all you need is a way to number the
> seconds and "anything" can do that.  Yes the PPS driver works with
> other non-NMEA ref clocks
>
> It would be good to get IRIG working.  One thing you don't say is how
> you are adjusting the levels.   Is it a digital control or an analog?
> In general you want to keep any digital control at maximum.  Reducing
> it even a little causes loss of dymanic range and reduces the
> effective with (number of bits) of the sample.  In the extream case
> your nice 24 bit WAV file is turned into 4-bit wide samples.   Such is
> the nature of integer math.
>
> Also if you are using the bui8lt-in sound on some PC, quality varies a
> lot. I'd start with a quality external audio interface.  But eiother
> way.  I think the first step is to look at the audio.  capture some to
> a file then look at the waveform using an audio editor.  Check for a
> reasonable amplitude with no clipping.  You will need to adjust the
> analog gain to get a good signa
>
>
> --
> =====
> Chris Albertson
> Redondo Beach, California
>
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