Operation; Introduction; Basic Power-Up Description; Frequency Adjustment - HP 10811A Operating & Service Manual

3-1. INTRODUCTION

3-2. This section contains operating information including operating characteristics and operating
procedure.

3-3. BASIC POWER-UP DESCRIPTION

3-4. The following paragraph is a basic description of the actions occurring when power is applied to
the oscillator. This description assumes the oscillator is at room temperature (25°C).
3-5. When power is applied to the oscillator, 10 MHz will appear at the output. The oven controller
circuit will go into its full warm-up mode. In this mode the maximum heating power is applied to
the oven mass. The oven mass is a metal casting surrounding the oscillator circuits and crystal.
The OVEN MONITOR output will be approximately 1.5 volts below the oven power supply voltage.
In about 10 minutes, the oven will have heated to the proper temperature. The oven controller will
begin to regulate at this temperature, and the OVEN MONITOR will drop to approximately 3.5
volts. It is normal for the oven current to drop momentarily to a low value when the oven
temperature first reaches maximum. This lasts less than second and is a typical circuit action.
3-6. After the first 10 minutes have passed, the oscillator may be initially adjusted using the following
procedure. The oscillator should be readjusted after 24 hours for maximum accuracy. Periodic
adjustment schedule can be determined by the procedure described in

3-7. FREQUENCY ADJUSTMENT

3-8. The frequency adjustment is the only periodic adjustment required. This may be initially adjusted
after 10 minutes of warm-up and then readjusted after 24 hours.

3-9. FREQUENCY ADJUSTMENT PROCEDURE

a. Connect reference frequency standard (multiple or submultiple of 10 MHz) to the EXTERNAL
SYNC INPUT of the oscilloscope.
b. Connect oscillator output (10811A/B) to Channel A. Set the sweep speed to .1 μs/div.
c. Set the oscilloscope to EXTERNAL TRIGGER and adjust the oscilloscope so that its sweep is
synchronized to the reference frequency. The pattern will appear to move.
d. Using an insulated tuning tool, adjust oscillator frequency adjustment (FREQ ADJUST on the
10811AIB) for minimum sideways movement of the oscilloscope pattern.
e. By timing the sideways movement (divisions per second on the oscilloscope), the approximate
offset can be determined based on the oscilloscope sweep speed shown in
12
SECTION III

OPERATION

Model 10811A/B
paragraph 3-10.
Figure 3-1