[time-nuts] WWVB BPSK Receiver Project?

Thu Mar 15 03:07:21 UTC 2012

> John
> Like your thought. I seem to remember costas loops work like that to
> recover the carrier.

Paul,

It recovers a bipolar signal to steer the local VCO as well as the data..
It also needs a quadratue hybrid at the VCO frequency (although it might
be fairly easy to make a quadrature oscillator vat 60 kHz.)

> Had seen it in amsat many years ago. So perhaps an approach is to limit
> if possible the incoming signal.

I'm not sure if it works properly with clipped (digital) dignals, off hand.

> Though further simple dumb thought. A NE602 or SA602 or also teh 612
> series. All the same mixer circuit (Or multiplier)will double the incoming
> frequency if you delay the incoming by 90 degrees I think.

Sine and Cosine are orthogonal. You need to do (Sine)*(Sine)

sin^2 (wt) = 1/2(1 - cos (2wt)

>Its a sensitive chip and has a 17 db conversion gain and is $2.40 at
> digikey. 8 pin dip. though what ever the delay at 60KC thats a long
delay. ;-)

The delay (phase shift) is not needed.

Best,

-John

=============

> Regards
> Paul
>
> On Wed, Mar 14, 2012 at 10:12 PM, David I. Emery
> <die at dieconsulting.com>wrote:
>
>> On Wed, Mar 14, 2012 at 05:13:47PM -0700, J. Forster wrote:
>> > Now it looks like they are going to kill WWVB, which is a bit more
>> > involved, but works.
>> >
>> > GPS is not an option without a tall tower.
>>
>>         Everything you say up to this makes perfect sense, but what
>> makes
>> you think GPS timing fails to work with less than a tall tower ?
>>
>>        I believe it is readily possible to get to the 10-30 ns of
>> UTC/TAI TOD area with just reasonable sky view, not 100% as implied by a
>> tower. And certainly 1E-11 or 1E-12 frequency accuracy is also readily
>> available with less than perfect sky view depending on your taus...
>>
>>        Perhaps ultimate performance requires really unobstructed sky
>> view
>> in order to absolutely minimize multipath but then you are probably
>> talking 1E-13 or better...
>>
>>
>> > This is NOT progress, IMO.
>>
>>         Virtually ANY GPS timing solution ought to easily get you inside
>> of
>> a couple of microseconds of UTC/TAI, I am pretty sure it is quite
>> difficult
>> to get within 10-100 us with the current AM modulation of WWVB, possibly
>> even 1-10  ms is difficult.   And anything close to this requires
>> accurate
>> knowledge of geographic position and 60 KHz propagation corrections.
>>
>>        I'm not clear how accurately one can resolve the phase transition
>> in the new scheme, but I suspect probably unambiguously to 1 cycle of
>> the 60 KHz... and from there is merely a function of how accurately one
>> can resolve the phase of the 60 KHz.    This potentially can supply a
>> much higher resolution time hack than the AM envelope.
>>
>>        The real question being how important is preserving backward
>> compatibility with antique equipment versus better performance...
>>
>>        I agree that ALWAYS is a trade off...
>>
>>
>> >
>> > -John
>> >
>> > ==============
>> >
>> >
>> > > Hi John:
>> > >
>> > > They are going to maintain the existing AM modulation format so all
>> the
>> > > WWVB "Atomic Clocks" will still work.  The phase
>> > > modulation is added on top of that.
>> > >
>> > > Yes, I expect my HP 117 may no longer work, but I'd much rather have
>> the
>> > > improved s/n and timing accuracy.
>> > >
>> > > Have Fun,
>> > >
>> > > Brooke Clarke
>> > > http://www.PRC68.com
>> > > http://www.end2partygovernment.com/Brooke4Congress.html
>> > >
>> > >
>> > > J. Forster wrote:
>> > >> All very nice, but if this change renders all existing receivers
>> > >> useless.
>> > >> How does that improve things?
>> > >>
>> > >> All it does is wipe out all the existing phase tracking
>> infrastructure.
>> > >>
>> > >> The only benefit is to the government who can reuse the WWVB
>> transmitter
>> > >> and frequency allocation. Everybody else will have to buy new
>> stuff.
>> > >>
>> > >> Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by
>> making
>> > >> scrap.
>> > >>
>> > >> YMMV,
>> > >>
>> > >> -John
>> > >>
>> > >> ==============
>> > >>
>> > >>
>> > >>> Dear Time-Nuts,
>> > >>>
>> > >>>
>> > >>>> I sure would like a WWVB BPSK receiver for the new modulation.
>> (..)
>> > >>>>
>> > >>>> I'm sure in time there will be plenty of low cost ICs designed to
>> > >>>> receive the
>> > >> [SNIP}
>> > >>
>> > >>
>> > >> _______________________________________________
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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."
>>
>>
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