[time-nuts] Ultra High Stability Time Base Options for 53132A
Richard (Rick) Karlquist
richard at karlquist.com
Mon Apr 13 14:19:09 EDT 2015
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
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