Well guys, my rubidium standards are now finally back in Switzerland
And I have a few good ones too, didn't have time to test them all, though.
Good thing is that there is still plenty of rubidium left in the lamps. I disassembled one unit that didn't lock and looked at the lamp and there is a big blob of rubidium visible in the back
.
It's easy to reassemble it back, you only have to push both the lamp and the rubidium cell back into that middle piece and solder the wires back in.
But before I do that I want to see whether I can reverse engineer the driver electronics and make the lamp run without the the rest of the assembly to take some pictures of that awesome rubidium glow. It looks really cool IRL (somewhat similar to potassium, which isn't surprising) unfortunately most cameras are unable to capture the full spectrum (looks far more purplish/red IRL). Tomorrow I'll compare phases of a few rb-standards over long time on my Tek scope to see how accurate they are. Maybe I can score a cheap 1PPS GPS receiver sometimes and use it as trigger source.
BTW, the coil for the inductively coupled rubidium plasma bulb runs at 147.4 MHz, with a few sidebands. (used a wire loop to pick up the magnetic field at the wires)
And that addon PCB inverts the lock signal: (wasn't already mentioned, so I thought I add it)
9 pin Sub-D pin 3: => 5V if locked, 0V if unlocked
10 pin rectangular connector on addon PCB: => 0V if locked, 5V if unlocked
Do I need a level shifter for RS-232 (from PC)? IIRC, RS232 from PC is +/-15V, while the LPFRS says it wants TTL (0/5V).
But now I have to go sleeping, it is already dawn outside