[time-nuts] WWVB PM Time Questions

[John Magliacane]

Greetings to the group!

I've been an FMTer for years, and an occasional "lurker" here, but as I find my ears occasionally "whistling" from time to time, I thought it was time to join in.  :-)

> On Jul 22, 2020, at 3:51 PM, paul swed <paulswedb at gmail.com> wrote:
>
> Ray watch out for my comment on the KD2BD solution. That oscillator isn't
> available and I have not been able to map something else into it. Tried
> several good grade Oven oscillators. Just be aware of that issue.
> Would need to do more tinkering and simply don't have that time right now.
> Also it would be great if the oscillator was something that could be
> obtained at a reasonable cost. I do not believe at all it has to be a
> OCXO as the older true time and spectracoms were not and they locked solid.
> So its a case of getting the control voltages right.

As Paul correctly stated, the Bomar VCTCXO used in my WWVB Frequency Standard is no longer available, at least in single quantities.  Fortunately, there are MUCH better alternatives available, but they require a little "finagling".  Hopefully, this information will help.

I have successfully used a Taitien model TTEAMCSANF-10.000000 High Precision VCTCXO in my frequency standard with excellent results. This oscillator operates on 3.3 volts, and produces about a 1 volt p-p clipped sinewave output. It has a +/- 5 ppm pulling range, and is controlled by a positive slope tuning voltage between 0.5 and 2.5 volts.

I've used two of these oscillators so far (in different projects), and both seem to tune exactly to 10 MHz with a tuning voltage close to 1.551 volts. However, YMMV. Use these numbers as a guide if your oscillator should have different specs.

The attached schematic shows the original circuit at the top with the modified circuit at the bottom. A 3.3 volt LDO powers the oscillator, and a simple MFP-102 JFET amplifies the output to drive the subsequent 5-volt CMOS logic.

The original oscillator was temperature sensitive, and took several minutes to warm up and settle down.  I often had to manually tune the oscillator on power-up using the front panel tuning control to get it in the ballpark where it would eventually lock to WWVB.

Now when I turn it on, the new oscillator locks to WWVB in about 30 seconds, and just stays there. :-)

Digikey carries it for $13.81.


73.000 de John, KD2BD
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