[time-nuts] new WWVB BPSK dev board

[Bob kb8tq]

Hi

Again to re-go over what has been said in the past:

Unless they start filling the “extra” bits on the WWVB signal with something 
(are they doing this ????) the whole modulation pattern is predictable. Once
you know what time it is “now” what happens from then on can all be calculated. 
I believe TVB has already done this part of it.

A “proper” receiver might take the AM and PM modulation signals and generate 
an “expected” signal from them once the time now is known. Correlating against 
that signal would seem to be the way to get this done. 

The one thing the Everest chips do indeed do is demonstrate that initial signal 
acquisition can be done under really awful conditions. Getting the same info off 
of WWVB with AM only …. not so much ….At least not so much with a receiver 
chip that is out on the market. 

Bob

> On Dec 4, 2018, at 4:21 PM, Attila Kinali <attila at kinali.ch> wrote:
> 
> Moin,
> 
> On Mon, 3 Dec 2018 18:11:30 -0800
> "Tom Van Baak" <tvb at LeapSecond.com> wrote:
> 
>> At long last, a complete WWVB 60 kHz BPSK dev board is available:
>> 
>> https://universal-solder.ca/product/everset-es100-cob-wwvb-60khz-bpsk-receiver-kit-with-2-antennas/
>> 
>> Note it includes the antenna(s). Also has links to documentation.
> 
> 
> As this is becoming a topic again, and the EverSet people still
> claim that the BPSK modulation of WWVB makes it more resilient
> to jamming and easier to receive, I would like to restate
> what I've written some years ago [1,2]:
> 
> BPSK by itself does not improve timing. At most it improves reception
> by having a constant power envelope. But in case of WWVB, where
> the AM modulation is still kept, this is not the case. The phase
> changes do not help reception at all. In order to help reception,
> one needs to send a _known_ bit string in order for a corrolator
> in the receiver to pick the signal out of the noise. The only
> known bits in the BPSK signal are the first 12 bits of each minute.
> Compare this to DCF77 which encodes 512 bits every _second_.
> Ie while DCF77 gets something like 10-20dB  easier to pick out
> of noise, but when using BPSK, WWVB gets... uhmm..  zero improvement.
> 
> All the BPSK modulation of WWVB does is
> 1) Make the signal unusable for any carrier phase tracking receiver
> 2) Add a second type of bit stream onto the signal for additional
>   information to be encoded
> 3) Generate a revenue stream for companies who sell new WWVB receivers.
> 
> For more information, read [2]
> 
> 			Attila Kinali
> 
> [1] https://www.febo.com/pipermail/time-nuts/2013-July/060456.html
> [2] https://www.febo.com/pipermail/time-nuts/2013-July/060471.html
> 
> 
> -- 
> <JaberWorky>	The bad part of Zurich is where the degenerates
>                throw DARK chocolate at you.
> 
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