[time-nuts] EFC Input pin impedance for the HP 10544A and 10811-6011

Mike Feher mfeher at eozinc.com
Sun Oct 28 21:22:16 EDT 2007

According to the schematic in the 10811A manual, the EFC goes to a 100K ohm
resistor, then the varicap, and then the other side of the varicap through
another 100K ohm resistor to the reference of 6.4 volts. The manual does not
call out a DC input resistance, but, this should give you an idea. - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of xaos
Sent: Sunday, October 28, 2007 9:14 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] EFC Input pin impedance for the HP 10544A and

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Hello everyone,

Does anyone know the input resistance of the EFC pin for the
HP  10544A and 10811-6011 OCXO's?

I have the spec sheet but it is not listed.

Can I assume something like 50K? This the the value for Crystek devices.


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