-------- In message <59dc074a-3a09-6315-29d4-6877c3bf7...@rubidium.dyndns.org>, Magnus Danielson write s:
>> With respect to precision machining, that space has changed a lot >> over the last five years, with precision CNC machines, factory >> or home-built, dropping dramatically in price. > >You need to tune it regardless. First: Yes, but if you pick a sensible vibration mode for your microwave resonance, that can be done with an screw-in endcap. Second: No, I would actually not need to tune it. Historically resonance cavities were used so that step/avalance diode multipliers had enough power to excite them. Today we have semiconductors which work at those frequencies. Later people kept the resonance, because it works well with low power budgets in telecoms/milspec applications. But the resonanance leads to all sorts of trouble, including frequency pulling, temperature sensitivities etc. We're neither space nor power constrained, we'd probably be perfectly happy if the end result is 4U and 100W, so resonance is not mandatory. Third: A lot of the "everybody knows" about which atoms can be used for active vs. passive atomic standards comes from the state of the art electronics about 30 years ago. Using laser-pumping and modern semiconductors, it might actually be possible to detect the 6.8GHz photons from the Rb. They won't be coherent photons, like in a Hydrogen maser, but we don't need them to be, in fact that just causes the same exact problems as the tuned cavity anyway, as long as we can measure the frequency well enough. (No, I havn't done the math on this, my wife has banned me from starting any new projects until our house is finished.) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.