[time-nuts] reference oscillator input circuit

[jimlux]

Rick Karlquist wrote:
> jimlux wrote:
>> I'm looking for suggestions on a general circuit that can be used to
>> receive an external frequency reference (nominally a real clean sine
>> wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it
>> into a "real clean" square wave.  Galvanic isolation is a plus (a
>> transformer or capacitor would probably do that).
> 
> In the 5071A at 80 MHz, we capacitively coupled a sine wave into
> a 74AC series logic gate, that had DC bias resistors to hold
> it at half the supply voltage.
> 

that's similar to what Said recommended last year.. he uses a big 
resistor from output to input to set the bias, rather than a divider.