Alpha Geek Clock: Battery Refresh

A pair of D cells can power an obsolete / out of production C-Max CMMR-60 WWVB receiver for about five years and, having the plastic pieces for a blinkie at hand, junking the faded case in favor of a test lashup seemed appropriate:

Given the fragility of that ferrite bar, I should conjure a wide D-cell base, a bar holder to cover the ends, and a PCB mount of some sort.

The receiver data pin drives the red LED of an RGB piranha through a 2.2 kΩ SMD resistor, so it’s visible in a dim room. Given that the thing flickers constantly during WWVB’s poor-reception daylight hours, reducing the LED current counts for almost everything.

The antenna has a cap under that heatshrink tubing, which called for a resonance check:

The blue dingus is an RF sniffer driven three orders of magnitude below its frequency spec:

The antenna response peaks where you’d expect:

Given the broad peak and typical tolerances, it’s spot on.