Yesterday I built a 10.000.000 divider with a small cascade of 74LS390’s to divide the rubidium 87 (Rb87) locked 10,000.000.00000(0) MHz from my Efratom FRS into 1 Pulse Per Second (PPS). I know that there is a another approach available. However, I managed to program a 16F648A PIC, but the contrapsion did not work. Perhaps the code needs a 16F84.
But… I am more into hardware anyway.
I built the divider on a small piece of epoxy bread board and combined my frequency standard with an “is locked, PPS works, and ready to use”-indicator. Thus, when the standard is switched on, several minutes later the PPS led starts to flicker.
The divider is depicted on the right (click to enlarge).
The PPS is shaped by a one shot generator (LS123) and the PPS width is approx. 75 ms.
A PDF of the -straight forward- schematic diagram can be downloaded here.
An advantage is that the PPS error is reduced by several orders.
This is a picture of the divider built into my Rubidium standard.
So, my Rb standard will now produce a ‘rock solid’ 1PPS for ntp.remco.org !
Designer Duffle Bags…
I found your site on technorati and read a few of your other posts. Keep up the good work. I just added your RSS feed to my Google News Reader. Looking forward to reading more from you….
Absolutely brilliant. I build clocks, and have been using GPS to drive them. I have been looking for some time to be able to integrate my rubidium oscillators into my clocks and you have shown me the way (i couldn’t make the PIC work either).
Thanks,
Crash
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