GPS vs WWV data stream

[WA4AOS]

I understand WWV will shut down operations soon and there are groups trying to get the feds to continue to fund this viable service.
Does anyone know if the data stream used on GPS is the same as used with WWV? I'm considering a very low 1mv DDS transmitter for 5 or 10 MHz and feed the GPS data into the xmitter. My need is to keep my old Heathkit GC 1000H clocks going wo retrofitting each unit with a GPS rx.

Any thoughts?

Glenn WA4AOS

[fourfathom]

I think this WWV shutdown story is old news, and never came to pass.  There was a 2019 federal budget proposal that would have shut down WWV transmitters, but that wasn't approved, and as of 2020 WWV funding seems to be adequate.  I even see that there was a 2021 WWVB upgrade, supposedly completed a few months ago.

[james_s]

I hope that's the case. I also have a GC-1000, it's one of my prized possessions. I also have about half a dozen devices that rely on the 60kHz WWVB signal. Most people probably don't know what WWVB is, but there are hundreds of millions of "atomic" clocks that rely on it to work.

[james_s]

They are indeed unrelated, WWV, WWVH and the GPS satellites each have their own independent array of atomic clocks. The clocks themselves should be comparably accurate but in practice GPS is likely to be more accurate due to propagation characteristics of the shortwave and LF broadcasts that WWV uses. 

[jpanhalt]

As one might say, it depends on what you mean by "more accurate."

The difference is that GPS time is not corrected to match the rotation of the Earth, so it does not contain leap seconds or other corrections that are periodically added to UTC.  As of January 2017, GPS time is 18 seconds ahead of UTC because of the leap second added to UTC December 31, 2016.

Google: Difference between UTC and GPS time

In terms of UTC, WWVB is more accurate.

[MIS42N]

There is a relationship between the time provided by GPS receivers and the various WWx broadcasts. The GPS time does not have leap seconds because it complicates the navigation calculations. However the GPS transmissions give the offset between GPS time and UTC so a GPS receiver reports time in UTC. The GPS and WWx broadcasts are related back to NIST. See https://www.nist.gov/pml/time-and-frequency-division/time-distribution. The conversion of GPS data to WWVB format has been tackled, see https://www.anishathalye.com/2016/12/26/micro-wwvb/

Deriving time from GPS is probably better than using the WWx broadcasts because the propagation delay correction has already been worked out by the receiver, the time should be within 100ns. Unless you know the distance between the WWx transmitter and your receiver to better than 30 meters, the GPS should win.