[time-nuts] WWVB d-psk-r update. Seems a reasonable solution

Dale J. Robertson dale at nap-us.com
Fri Mar 29 09:28:21 EDT 2013

If I'm not mistaken, the oscillator frequency needs to be an integer multiple of 240 KHz.

Sent from my iPhone

On Mar 29, 2013, at 8:37, Bob Camp <lists at rtty.us> wrote:

> Hi
> There are a variety of VCXO's and TCVCXO's on the Mouser site. Prices seem to range from $3 to $10 for the reasonable candidates.
> http://www.mouser.com/ProductDetail/Fox/FOX924B-10000/?qs=sGAEpiMZZMsBj6bBr9Q9afDupvxlfd2QBmF8W0236Ww%3d
> Is one of the many. It runs at 10 MHz, CMOS output, and actually *is* in stock. Price is $6.41 for a single piece. I'm sure that a bit more digging could get that down a bit. The auction sites also have similar parts.
> Bob
> On Mar 28, 2013, at 9:01 PM, paul swed <paulswedb at gmail.com> wrote:
>> OK it has been a while and I have promised to share results. In the next
>> few days I will put whats on paper into a schematic and share. I won't
>> dwell on all of the stuff from October to now. But several front end rcvrs,
>> and several analog Costas loops were built using MC1496s and another using
>> AD633 multipliers. Various other glue.
>> Nothing to rave about.
>> What I will detail is what I have done with quite common parts. But what it
>> isn't is a kit or absolute or anything else. It can be made better. Don't
>> doubt that for a second.
>> So what I do have are 4 pretty simple and reasonable parts of the solution.
>> It really does work even on the east coast. Though MSF can really cause
>> issues ocasionally. One key part the costas loop is a design I stumbled
>> across from 1971 designers casebook electronics magazine ca herbst. Was
>> cleaning out old papers. The article left a lot of detail out. But the
>> principle is solid. It was surprising at how well it worked the first time.
>> So what I will share with the Time-nuts are the following schematics.
>> A 60 KHz TRF receiver. Takes a 1uv signal and increases it to 2-4 V PP with
>> AGC and soft limiter. It includes a 60 Khz xtal filter to set the passband
>> and a tuned stage or 2. There are quite a few possibilities on the
>> internet. Tried a few. This is my version. But others would work just as
>> well.
>> Digital costas loop using nothing more the a 74hc86 quad exclusive or.
>> Resistors and caps to integrate.
>> The 12 Mhz VCO. Why 12? Thats the crystals I have. Boy can this area use
>> some help.
>> The divider. Cmos 12 Mhz to 0 and 90 degrees at 60 Khz. This is straight
>> out of any digital application manual. No magic at all.
>> When combined this creates a complete WWVB costas loop solution that
>> delivers a 60 Khz output locked to wwvb without the phase modulation. A
>> byproduct is the digital data from the new signal. Not used. Not even to
>> drive a led.
>> A path could be added that literally inverts or not the original AM signal
>> so that spectracom 8170s and Truetime DC60s would work and recover time
>> correctly. That is a piece O cake.
>> So I will get this into a schematic to share over the next day or two.
>> By the way on performance the system handles sun rise and sets and keeps
>> ticking. Using a fluke 207 driven by a Rb ref to watch for failures. This
>> is recorded on a 4 channel chart recorder program on a laptop. I have used
>> the system to drive 2 X HP VLF 117s and they track as w
>> Lots of areas that might be improved AGC control and time constants. Adding
>> a opamp to the 0 degree phase VCO control voltage and also adjusting Time
>> constants. Though the 12 Mhz oscillator is really standard parts just could
>> not find something reasonable and off the shelf. Digikey or Mouser stuff.
>> something with 4 pins and a few $. By the way the control voltage is
>> .5V/.1Hz.
>> Regards
>> Paul
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