[time-nuts] WWVB remodulator for the Spectracom 8170...

[Bob Camp]

Hi

The receiver you are driving with the modulator should be quite happy with >
300 mV p-p as a signal level. There's no need to put 3, 4 or 5 V out of the
beast. If you have a 500 ohm to 50 ohm L pad on the gate, it should not draw
much current at all to drive the load. I think that keeping the level as low
as possible is a good idea RF wise. You don't want leakage of the local
signal masking the real WWVB.

Bob



-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of paul swed
Sent: Tuesday, June 18, 2013 10:52 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] WWVB remodulator for the Spectracom 8170...

Interesting the HC will work all the way down to 2.2V so everything can be
run from 3 Volts.
No idea as to the effect of the xtal oscillator maybe the 3.9 M R needs to
be changed.
It also appears that the HC chip may doing the lions share of current
consumption. Spec sheet says up to 20 Ma. Hard to believe actually.
As for driving lengths of wire over distance it needs to be a buffer chip.
74hc244. But that seems like serious overkill it can drive 20 ma per port.
Maybe a cd 4049...


On Tue, Jun 18, 2013 at 6:41 AM, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> I don't know of any phase tracking receiver that would be bothered by the
> modulator in Paul's schematic. You could implement it a couple of ways,
but
> the net result would be the same.  The AM is a bit more square wave than
> the WWVB signal. Modulation depth and timing would / could be dead on.
>
> Bob
>
> On Jun 17, 2013, at 9:29 PM, David I. Emery <die at dieconsulting.com> wrote:
>
> > On Mon, Jun 17, 2013 at 06:11:15PM -0400, Bob Camp wrote:
> >> Hi
> >>
> >
> >> The Costas loop already has the AM component available. There's no
> >> need for a second receiver, just wire the AM output over to the output
> >> modulator.
> >
> >       That is standard for most Costas loops with an I arm... haven't
> > looked at his schematics carefully yet... possibly one might need some
> > kind of AGC to use it as input to  a second double balanced mixer
> > serving as modulator in order to get the right 14 (?) db AM as signal
> > fades slowly.   Not sure how deep the diurnal fades are...
> >
> >       But I guess if everything is quite linear over enough of a range
> > one could perhaps just remodulate without AGC and create a replica of
> > both the modulation and fades on  the local 60 KHz carrier.
> >
> >
> >
> >
> >>
> >> Bob
> >>
> >> On Jun 17, 2013, at 5:57 PM, "David I. Emery" <die at dieconsulting.com>
> wrote:
> >>
> >>> On Mon, Jun 17, 2013 at 02:41:13PM -0700, Burt I. Weiner wrote:
> >>>> Chris,
> >>>>
> >>>> The 8170 was originally intended to be a frequency reference source
> >>>> tied to the USFS (United Stated Frequency Standard).  It also gave
> >>>> the time of day, but I believe that wasn't it's primary purpose.  As
> >>>> I recall, there were some versions that did not have the clock
> >>>> readout and some that had a chart recorder.  Back in the 80's I used
> >>>> to drool (it was a disgusting sight!) over the Spectracom receivers
> >>>> with the chart recorders.  At that time I was usuing a Gertsch RLF-1
> >>>> with an external Moseley 680 chart recorder.  The remodulator
> >>>> precludes it from being used as a frequency standard, but in my
> >>>> opinion, so does the fact that WWVB is now phase shifted a bunch.
> >>>>
> >>>> The 8170 uses a coherent detector and that's where the problem
> >>>> lies.  While the 8170 still locks to the WWVB carrier, the new BPSK
> >>>> scheme causes the detector to output bad data in spite of the
> >>>> original dips in the carrier still being present.  I had always
> >>>> wondered how it was able to pull the data out the noise, but never
> >>>> had a manual until just recently.  I had naively assumed that the
> >>>> WWVB new BPSK scheme would not affect the time of day aspect of the
> >>>> 8170.  Like I said, I only use it as a clock in my shoppe, and being
> >>>> an old dog I don't easily learn new tricks such as looking in a
> >>>> different direction for one of the other clocks.
> >>>
> >>>     I suppose I am stating the obvious, but why not combine Paul
> >>> Swed's Costas loop and this scheme to output a phase locked 60 Khz
> >>> with the right AM modulation ?
> >>>
> >>>
> >>>
> >>> --
> >>> Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston,
> Mass 02493
> >>> "An empty zombie mind with a forlorn barely readable weatherbeaten
> >>> 'For Rent' sign still vainly flapping outside on the weed encrusted
> pole - in
> >>> celebration of what could have been, but wasn't and is not to be now
> either."
> >>>
> >>> _______________________________________________
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> >>
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> >
> > --
> >  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston,
> Mass 02493
> > "An empty zombie mind with a forlorn barely readable weatherbeaten
> > 'For Rent' sign still vainly flapping outside on the weed encrusted pole
> - in
> > celebration of what could have been, but wasn't and is not to be now
> either."
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com
> > To unsubscribe, go to
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