C-Max CMMR-6P-60 Receiver Polarity

It goes without saying: the positive receiver output (TCO: Time Code Output) on the CMMR-6P-60 WWVB receiver board tracks the received RF amplitude. In fact, it does go without saying: nowhere does the (rather skimpy) board doc mention that fact.

Receiver Delay
Receiver Delay

Here’s the output, driven from my WWVB simulator in the Basement Lab. Note that reduced RF corresponds to the active part of the bit, so the output goes low when the bit starts. Conversely, the inverted output (TCON: Time Code Output Negative) goes high, which may be more useful for some purposes.

Of interest: there’s maybe 12 ms of delay on the leading edge and 5 ms on the trailing edge. The received pulse duration is therefore different than the transmitted pulse by some amount. The doc says less than ±35 ms, so it can be longer than what you expect.

I can’t measure the actual RF amplitude at the receiver, but it’s barely above the rather high ambient noise level near all the test equipment. The receiver gives up a few feet away from the simulator’s bar antenna, which means I’m (probably) not corrupting WWVB receivers for miles around.