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

Bob Camp lists at rtty.us
Fri Mar 29 08:37:05 EDT 2013


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.


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.


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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