[time-nuts] IRIG-B audio decoder circuits and ICs sought

Neil Schroeder gigneil at gmail.com
Wed May 20 01:11:07 UTC 2015


A bc635 can be had on eBay for almost nothing. It's not a pleasant piece of
gear, but this is one task it can help you with greatly.

Tools exist to let you analyse the stream extensively, and the Api is
trivial to learn -but not super featured at the high level.

On Tuesday, May 19, 2015, Tim Shoppa <tshoppa at gmail.com> wrote:

> See for example the Truetime 820 decoder. Discriminators, One-shots, and
> Flip-Flops with pots to tweak the levels.
>
> Tim N3QE
>
> On Tuesday, May 19, 2015, Joseph Gwinn <joegwinn at comcast.net
> <javascript:;>> wrote:
>
> > I'm studying up on how IRIG-B decoder circuits work.  What are the good
> > approaches, the bad approaches, especially in the presence of noise?
> > (I asked on the NTP group, with little result beyond the C/C++ decoder
> > software written for the audio channel of a 1990s Sun workstation,
> > which it ate alive: 50% cpu load.)
> >
> > Are there decoder ICs available?
> >
> > The closest to a decoder IC I've found is some FPGA code from a partner
> > of Microsemi (nee Symmetricom):
> >
> > ..<
> >
> http://www.microsemi.com/products/fpga-soc/design-resources/partners/semquest
> > >
> >
> > All marketing and little technical information.  I'll have to find out
> > the details.
> >
> >
> > I find very little, though I did find one intriguing idea using a
> > Costas Loop to lock to the 1 KHz carrier, and a posting suggesting
> > squaring the input signal and phase-locking to the 2 KHz result.  Most
> > recent articles on IRIG decoders come from Chinese sources, mostly in
> > the AC power industry.
> >
> > Joe Gwinn
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