[time-nuts] Dephasing WWVB

[paul swed]

Yes indeed I have 2 X 599s also and the IF is complicated and if you don't
have the magical 60 KHz mod (I don't) you have to hack a solution. That I
did. Essentially double the vco and div by 2. While feeding the vco to the
mixer. Hey it worked most of the time and on a solid test signal always
worked and I mean for weeks.
The 60 KHz xtals existed and still may. Fun to tinker with and cheap.
In fact because if the IF scheme of the 599 thats why I went to an external
solution.
You can hack each rcvr internally to succeed. But thats hacking. An
external approach allows all of them to work. The 117s 207 spectracoms...

Hence the d-psk-r/costas loop soluyion released a year ago. But its semi
digital and analog and I have to say I never really figured out what the
magical VCO filter needed to be. Though I experimented. It works. But its a
guess.
Regards
Paul


On Mon, Jun 30, 2014 at 1:00 PM, John Reed <ka5qep at sbcglobal.net> wrote:

> First on the Schmidt trigger - The problem is that at the start of each
> "bit" that WWVB transmits the squared 60 KHz signal is essentially dead and
> the trigger must pick a new starting point.  This point seems to be random
> and can apparently end up as a positive or negative, so you end up with
> phase changes of 180 after the flip flop.  No trigger can fix this.  The
> system has to have some memory of the phase and this is why the Costas loop
> works.
>
> I thought about getting rid of the 100 KHz front end filter in the Tracor
> and seeing if I could modify it by squaring the LO signal.  This isn't
> straightforward either.  The Tracor has a complex method of generating the
> IF signal.
>
> I wasn't aware that 60 KHz crystals are available.  I would have used
> these instead of the LC filters.  I had some old telephone loading ferrite
> toroid coils, so most of the hardware was available.
>
> Thanks for all the comments on this.  At least I understand the problem
> now, and why the solution will take some work.
>
>
> John
>
> -----Original Message----- From: paul swed
> Sent: Monday, June 30, 2014 9:49 AM
> To: Martin VE3OAT ; Discussion of precise time and frequency measurement
>
> Subject: Re: [time-nuts] Dephasing WWVB
>
> Many of the old receivers use them spectracoms come to mind. They are big
> units and +- 40 Hz BW and I am totally unaware that they can be found
> today. That also goes for nice transformers and inductors to build higher Q
> circuits.
> I built a opamp chain and it worked well but those crazy amps do draw
> power. I like the ua consumption level. But thats a personnel preference.
>
> I used the 60 KHz watch Xtals and its in the schematics of the WWVB rcvr I
> released to time-nuts a year ago. These little crystals are interesting to
> work with and available from China 25 xtals for a few $ at the pay site. I
> purchased 2 packs so that I could sift through them. The trick is to very
> very lightly load them. I could learn much more about them actually. They
> seem useful overall.
> The first re-modulator used them directly as the 60 KHz source. I stepped
> up to the 15.360 MHz osc only because I believed they were not accurate
> enough and that turned out not to be the case as I found.
>
> The other comment to note is that these xtals cause an actual signal gap at
> the phase transition. Because at that point the signal is actually 2 X 60
> Khz. The crystal gaps for at least 8 cycles from what I have seen.
> Regards
> Paul
> WB8TSL
>
>
>
>
> On Sun, Jun 29, 2014 at 6:39 PM, Martin VE3OAT <ve3oat at storm.ca> wrote:
>
>  John Reed wrote :
>>
>> >
>> > By the way, my 5 section synchronous filter is an LC with
>> > op-amps between each stage to bring the gain up for the
>> > squaring chip.  It has a 2 KHz -6 dB bandwidth at 60 KHz.
>> >
>>
>> John, have you thought of using a single 60.0 kHz crystal as a bandpass
>> filter?
>>
>> I can't remember which receiver it was, but I think one of the old
>> commercial WWVB receivers used a crystal as the tuning element.
>>
>> ... Martin   VE3OAT
>>
>>
>>
>>
>>
>>
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