[time-nuts] new WWVB BPSK dev board

[jimlux]

On 12/4/18 9:00 AM, Tim Shoppa wrote:
> Because of the Q of WWVB's transmit antenna (at least 300 by my back of the
> envelope estimates), I don't think we could ever claim a WWVB PPS edge
> sharper than 5 milliseconds and that might be optimistic.
> 

Sure you can.. you do a matched filter to the waveform, so you're not 
just looking at a single zero crossing or cycle.  Getting fraction of a 
degree phase accuracy from a strong signal is entirely possible.

A Q of 300 implies a bandwidth of 200Hz, which would, if a single 
section, be a delay of a few milliseconds.  But that delay should be 
constant. What might be the limit on precision is whether the delay 
through the antenna and the ultimate radiated phase changes with, say, 
temperature or soil properties.



> Tim N3QE
> 
> On Tue, Dec 4, 2018 at 11:49 AM Bob kb8tq <kb8tq at n1k.org> wrote:
> 
>> Hi
>>
>> The I2C clock rate is going to matter a bit in terms of what you can
>> achieve.
>> Since the device is targeted at low power, the max practical baud rate may
>> not be very high. I2C can have a lot of wait in it ... There are a lot of
>> registers
>> dumped after each “reception attempt”.
>>
>> There also is the basic question of how the IRQ flag relates to the time
>> the
>> chip “sees”. If it’s actually WWVB time sync’d then that’s a useful thing.
>>
>> None of this is likely to be an issue in a wall clock. If they can run at
>> a “tens of ms”
>> sort of level that’s more than good enough. We really want to get to
>> microseconds
>> don’t we :)
>>
>> Bob
>>
>>> On Dec 4, 2018, at 11:25 AM, Majdi S. Abbas <msa at latt.net> wrote:
>>>
>>> $69 CAD is roughly $50 USD.
>>>
>>> Expensive for what it is but easier to work with than gutting a working
>> clock and no more expensive.
>>>
>>> I ordered one.  Curious to see what sort of precision we can get from an
>> i2c interface.
>>>
>>> If nothing else I suppose I can toss a six digit i2c 7 segment module at
>> it and roll my own WWVB desk clock.
>>>
>>> —msa
>>>
>>>> On Dec 4, 2018, at 07:50, paul swed <paulswedb at gmail.com> wrote:
>>>>
>>>> I assume thats exactly the case. I also thought it was pretty high.
>>>> The actual clocks are about $50 or less I believe. So the board seems a
>> bit
>>>> off.
>>>> Regards
>>>> Paul
>>>> WB8TSL
>>>>
>>
>>
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