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

Tim Shoppa tshoppa at gmail.com
Fri May 22 10:48:59 UTC 2015


On Thu, May 21, 2015 at 10:22 PM, Joseph Gwinn <joegwinn at comcast.net> wrote:

> The definition of "good" here is tenth-microsecond alignment between
> the 1PPS output of the decoder and the incoming IRIG-B12x signal.
>


> > From: Tim Shoppa <tshoppa at gmail.com>
> > To: Discussion of precise time and frequency measurement
> >       <time-nuts at febo.com>
> > Subject: Re: [time-nuts] IRIG-B audio decoder circuits and ICs sought
> >
> > See for example the Truetime 820 decoder. Discriminators, One-shots, and
> > Flip-Flops with pots to tweak the levels.
>
> Hmm.  Interesting.  URL?
>

I'm not sure 0.1us is a reasonable expectation to get PPS from the 1kHz AF
variant of IRIG-B.

1kHz AM IRIG-B was usually distributed across a site/range by
telephone-type wiring using interspersed audio transformers for isolation
in the long haul. It was used to drive simple displays that used 60's
transistors or 70's SSI chips, and also recorded on parallel tracks on
telemetry recorders. It's pretty cool because when playing back old
telemetry tapes we would just use the same clock display we did when live,
but when fed the audio from the recorder it showed us the time of
recording. (In some cases in the 80's, I got to work with telemetry tapes
that were 20 years old! Today they'd be 50 years old and you could still
play it back while watching the display). Sometimes we would slow down the
tape and on the pen recorders optimistically we could eyeball times with a
resolution finer than the 10ms bit rate, but not better than 1ms.

Tim.



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