FE-5680A Atomic Frequency Source

atomic frequency source

The FE5680A is quite well detailed on various web sites so I won't go into much detail. Its a Rubidium frequency source that was commonly used in telecommunications equipment. This particular unit is supposed to have a frequency output that can be set through a serial port connection but, as yet, I've not I've not been able to get any response to command. The unit currently outputs a 1us pulse at 1 second intervals (1pps), this isn't a problem for me but it would be nice to have a higher resolution to play with. On my clock I'm only going to have an hour hand and a minute hand so I'll just count to sixty and step.

The problem with an atomic frequency source is that it should be much more accurate than most measuring equipment, it certainly should be a great deal more accurate than my Rigol DG1022 Arbitary Waveform Generator, nevertheless I put the Rigol into counter mode, measuring frequency and was pleased to see a reading of 1.000Hz and a pulse width of 999.998ms.

1pps output on scope

1pps output

1pps period

The Feedback generator isn't connected anywhere, I'm inclined to test that through the Rigol now to see how accurate that is at an indicated 1Hz.

Another challenge is to set the time accurately, I'm going to look out for an old 'radio controlled' clock to salvage the receiver from, I'll then use the time signal from that to synchronise the clock; that means that I'll need some positional feedback so the controller knows where the hands are, I'm considering a couple of simple optical sensors for that, I think that a position encoder may be a bit unnecessary, even for this project!