[time-nuts] EFC Input pin impedance for the HP 10544A and10811-6011

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Oct 28 22:48:43 EDT 2007

Bruce Griffiths wrote:
> Mike Feher wrote:
>> While it is difficult to read the resistor values on that schematic (and as
>> Bruce points out not really relevant as the diodes are reverse biased), it
>> appears that since the varicap is referenced to ground, the 10544A's EFC is
>> always positive. The 10811A goes from -5 to + 5 as the cathode end of the
>> diode is referenced to +6.4 volts. All this time I had thought they were
>> fairly interchangeable. - Mike 
>> Mike B. Feher, N4FS
>> 89 Arnold Blvd.
>> Howell, NJ, 07731
>> 732-886-5960
The 1972, 1976 and 1975 datasheets specify an EFC range of -5V to +5V so
connecting the EFC varicap cathode to +6.2V would appear to be the standard.
Other specs like the power supply current specs change dramatically in
the 1976 datasheets.

There are also 10544A and 10544C variants which have dc oven controllers
rather than the switching oven controller of the 10544A.
The phase noise floor of these is about 20db lower than for the 10544A.


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