[Premium-Rx] RUBIDIUM FREQ STANDARD

[Ed Tanton]

Hi Dave... keep in mind rubidium standards need calibration to WWVB. There 
are receivers available that are designed for this (typically the Tracor 
900 series WITH chart recorder) or you can find a VLF (60kHz WWVB) receiver 
and buy a chart recorder/etc. The deal is that you are comparing the 
standard with WWVB over what amounts to a 72 hour or so period, nudging it 
closer as you go. It may seem like you don't need the charting if you're 
not trying to obtain NIST traceability... but *** I have no idea what the 
possible long-range cumulative error might be ***... AND why get a rubidium 
standard if you don't want it to be "RIGHT"?

As I said earlier, I still don't understand why rubidium requires 
calibration, and cesium doesn't. Yet, I DO believe you made the correct 
decision in getting rubidium instead of cesium. Granted this calibration 
business appears to be necessary, but the way the cesium standards work (as 
I understand it) is that cesium tubes have to run very hot to operate, and 
thus have a fairly finite lifespan... requiring replacement. Plus, they 
were 2 or 3 times the cost of rubidium when I bought my own Efratom 
rubidium unit.

All of the associated 'stuff' required is why I have never actually set 
mine up. That, and a disaster of a testbench that needs complete urban renewal.

As for your 'distribution'... I would provide a non-inductive load of 
whatever the standard wants, and take an LH0002 power line driver and use 
that. Take a look at one of the TI Line Driver data books (or National) and 
go from there. IF you could use 600 ohms, you could actually use dBm for 
whatever levels you want to try and spread around-although my impression is 
that most line drivers are intended for lower impedances.


73 Ed Tanton N4XY <n4xy at earthlink.net>

Ed Tanton N4XY
189 Pioneer Trail
Marietta, GA 30068-3466

website: http://www.n4xy.com

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