[time-nuts] WWVB Dephaser Question

[Bob kb8tq]

Hi

The “ideal” antenna solenoid would be a bit longer ( say 2 X to 5X ). 
The turns should be spaced apart by a few percent of the length.
( so turns over 30 or so … not so much …). 

How much better is “ideal” compared to “just get it done?”.  At least
from the stories that are told, it is significant. Since all these antennas
are very small (so non-ideal) it’s a bit of a snail race. 

Bob

> On Oct 12, 2020, at 3:42 AM, John C. Westmoreland, P.E. <john at westmorelandengineering.com> wrote:
> 
> Paul,
> 
> Doesn't the post by Chris Howard above appear to be a good/great starting
> point?
> Seems like that approach could be extended.
> 
> https://github.com/chris-elfpen/Teensy4WWVBsdr
> 
> 73's,
> John
> AJ6BC
> 
> 
> On Sun, Oct 11, 2020 at 9:23 AM paul swed <paulswedb at gmail.com> wrote:
> 
>> Good morning to the group. Both Rodger and I can answer the last question
>> on the questionable bits very well.
>> I have 7 antique devices spectracoms truetime fluke tracor Dymec etc.
>> They handle it very well each has at least a 2 second integration time. The
>> dpskr has always taken advantage of this fact. Literally we have run days
>> without flips in the charts. Even in summer.
>> Some surprises in doing this. Numbers of bits that could change don't seem
>> to. Then some of the bits have a really odd pattern but they follow the
>> pattern. Thats been coded into the dpskr. In fact anything over several
>> years we have figured out are coded in.
>> One thing we did not do was automatic change from summer to winter offsets.
>> Its really a PIA so just not that excited when this happy switch flipper
>> can do it in 1 second.
>> 
>> The other bit of fun for the magical new DPS wwvb receiver is after you get
>> the bits you must decode them and its nothing like the AM code. Its a M/N
>> FEC code. Its all in the NIST papers but was fun coding and I imagine every
>> bit as fun decoding. The dpskr software at least gives you hints to the
>> process.
>> 
>> Here is an offer. Anyone that gets the BPSK bits working through a SDR/DPS
>> arduino/STM cheap chip. Please no $100 FPGA development kits.
>> I will be happy to dig into the decoder. The solution needs a 1pps and the
>> bit.
>> Whats really funny about the wwvb bpsk is that there has never been sort of
>> a open development platform. Anyone who has played with the ES100 will run
>> into some issues that are annoying for a time nut to tinker with.
>> Regards
>> Paul
>> 
>> On Sun, Oct 11, 2020 at 10:39 AM Bob kb8tq <kb8tq at n1k.org> wrote:
>> 
>>> 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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