On 4/13/2015 3:11 AM, John Miles wrote:
A comparator with less open-loop gain was what they needed. Somebody at HP really liked ECL line receivers, though. Those were very noisy at HF, but this had little or nothing to do with their bandwidth (see my other post.) To square up a 10 MHz signal from an OCXO it's hard to beat a simple diff amp with a pair of bipolars, a la Wenzel. -- john, KE5FX Miles Design LLC
The HP counters all used ECL line receivers for the A and B channel to convert the input frequency signal to be counted into a digital square wave. Naive engineers then ape'd this for use on the timebase clock. Engineers at HP who actually knew what they were doing, such as Tom Falkner, did use differential pairs. However, HP being a huge company, the word did not necessarily get disseminated to all the other HP engineers. Rick Karlquist N6RK _______________________________________________ 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.
