How to build WWVH receiver (2.5, 5, 10, or 15 MHz) for Radio Controlled Clock

Using Arduino Project Guidance
1

I live in Oahu, and therefore too far away to receive the regular WWVB signal (60 KHz)from Ft Collins used for most Radio Controlled Clocks.

However NIST broadcasts (WWVH) the same signal on 2.5, 5, 10, and 15 MHz from Kaua'i.

So what's the easiest way to receive the time signal on any of those frequencies for processing on the Arduino?

Google searches seem to indicate lots of projects for WWVB but none for WWVH.

Any ideas from the community?

Thanks!

2

WWV and WWVH encode the date and time using a 100Hz tone, which is quite different than the way that WWVB encodes the time.
If you listen to WWVH with an AM receiver, and you shouldn't have any trouble hearing it from Oahu :), you can hear the 100Hz tone as a brief buzzing sound every second.
I first implemented a WWV decoder many years ago with an ADSP EZkit Lite and used it to keep my Amiga computer's clock on time.
All I did was use Goertzel's algorithm to detect the 100Hz tone and then distinguish the three tone lengths (Pulse, one and zero) and decode it from there.
I have done this on an Arduino and on a Teensy3 but I haven't played with that code for probably at least two years.

A different approach I used was to detect the 1kHz tone that occurs every minute on WWV (except on the hour) and use that to synchronize a DS3231 RTC. As long as the RTC doesn't drift more than 29 seconds over the course of a day (to allow for times when the signal isn't received) it will keep the RTC on time.

Pete