[time-nuts] WWVB Dephaser Question

[Bob kb8tq]

Hi

The “simple” approach is to generate the full modulation pattern
for the signal based on a “known good” time source. There are a 
couple of ambiguous  bits so it will only be close. Feed that into
your inverter and the result will be (near) clean WWVB. Since you
never demodulate the WWVB, there isn’t a lot to the RF side ….

There will be some drops and pops. The question will be just how
well this or that antique device deals with them. 

Bob

> On Oct 10, 2020, at 10:01 PM, paul swed <paulswedb at gmail.com> wrote:
> 
> The additional article John sent us is a pretty good read. Having soldered
> all the little wires together with heat shrink, I can see the advantage of
> the epoxy approach.
> 
> A consideration for the discussion. So far its been about the various tried
> and true methods for a RF frontend. But the real challenge that is in front
> of us is the software that uses that frontend. How about a very easy to
> build a phase flipper so that those that are software inclined do not need
> to deal with the frontend to get going. The dpskr has a phase flipper in it.
> But it can be even simpler than that.
> 
> A 60 KHz logic signal ( divide 6 Mhz down or anything else thats easy)
> Feeds an inverter to generate the 180 degree phase. A gate to select 0 or
> 180 degrees. All of the gates/inverters can actually be a single quad
> nand gate. A D flip flop with the clock from the 0 degree 60 KHz logic
> level. Your data into the D input. The D flip flop synchronizes the data to
> the clock. On the output you can filter the signal or not and cut the level
> down or not.
> Its a BPSK source.
> Granted in a pure gate approach the actual bpsk flip will not be the 2 X 60
> KHz for 1/2 cycle. But in real receivers the 120 KHz never comes through
> the various stages and filters. So no real harm. This also doesn't supply
> the AM signals 14-17 db modulation. But its good enough to allow software
> to be developed and its simple.
> Good luck
> Paul
> WB8TSL
> 
> On Sat, Oct 10, 2020 at 2:05 PM John Magliacane via time-nuts <
> time-nuts at lists.febo.com> wrote:
> 
>> For WWVB reception, I use a single turn of 40-conductor ribbon cable,
>> configured as a 40-turn loop, brought to resonance with a parallel
>> capacitance, that differentially drives an instrumentation amplifier. No
>> electrostatic shielding is needed to eliminate e-field pickup with this
>> approach.
>> 
>> The antenna hangs in my attic with thumbtacks and does a commendable job,
>> day or night, 1622 miles east of WWVB.  See attached JPEG image.
>> 
>> The March 2017 issue of "Circuit Cellar" magazine described an "improved"
>> version of my antenna/preamp combination (which I haven't looked into).
>> See attached PDF document.
>> 
>> During my early experimentation, I realized that the preamp would need to
>> have a high dynamic range in order to perform well in the high-noise
>> environment that is LF.   And if the preamp is going to feed a receiver
>> through any reasonable length of coax, it will need to be able to drive a
>> high capacitance load as well.
>> 
>> 
>> 73.000 de John, KD2BD
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