The clock still isn’t in a case, I managed to find a metal case just big enough for the receiver board, so I trimmed the receiver board down to size to get it in, to then discover that it hates metal boxes and stops working all together, d’oh!
I’ve spent a long time reworking the PIC code, to try and make it more robust, and have it decode the time successfully more often. As the official NPL Datasheet shows, 2 bits are transmitted a second. To decide whether you’ve received 00, 01, 10 or 11 in any second, you look at the length and timing of the pulse that is sent. The PIC code used to sample the incoming pulses 3 times, and then make a decision on what the received digital bits were based on those 3 samples. I have now reworked the code so that the incoming pulse is sampled 300 times, and averaging is used to decide whether the incoming pulse should be 00, 01, 10 or 11.
Still need to put it in a case though!