Frequency Standard Calibration

TM 11-5820-918-13

c. Set up the equipment as shown in figure 5-9. Set the 1024 to the 2-30 MHz

range.

d. With the 1024 MODE switch in MAN position, press RESET, then press START.

During the sweep, manually sweep the spectrum analyzer to keep the TCS-4B Trans-

mitter signal within the displayed 1 MHz wide range of the analyzier. All spurs and

the phase noise floor around the fundamental should be at least 40 dB below the fun-

damental, except within 50 kHz of the fundamental.

e. If any spurs, or the phase noise floor, are not at least 40 dB down, except

within 30 kHz, replace the sweep synthesizer, (1A1) in the 1024. Repeat the measure-

ment after replacement of the sweep synthesizer.

f. If spurs and/or phase noise persist, re-install the original sweep synthesizer,

and replace the frequency standard (1A3). Repeat the measurement after replacing

the frequency standard.

FREQUENCY

STANDARD

5-34. CALIBRATION REQUIREMENTS. The TCS-4B internal frequency standard

(1A3) may be calibrated to a known station standard by following the procedures out-

lined in paragraph 5-35. This procedure should only be used if the station standard

-9

is known to be accurate and of a stability (aging rate) better than 1 x 10 /day, such

as a precision ovenized quartz crystal, cesium beam, or rubidium beam standard. The

1024 should be operated continuously (AC line power on) for a minimum of three days

to allow the internal 5 MHz crystal oscillator to stabilize before calibrating.

5-35. CALIBRATION PROCEDURE.

a. Carefully remove the top cover of the 1024 sweep generator with the AC line

power left on, after the 1024 has been running for at least three days.

b. Connect the 1024 rear panel jack J5 (5 MHz out BNC) to channel 2 of a dual

Connect channel 1 of the scope to the station (either 1 or 5 MHz).

d. Set the scope for either ALTERNATE or CHOP sweep mode, triggering on chan-

nel 1 only; i.e. trigger scope on station standard only. Set scope time base to 0.1

us/div.

e. Adjust scope trigger level control to obtain a steady scope display of the station

standard waveform (1 or 5 MHz) on channel 1.

f. The 5 MHz TCS-4B output from 1024-J5 on channel 2 of the scope should be

a 5 MHz pulse stream about 4 volts peak-to-peak in amplitude that appears to drift

or slide to the right or left relative to the house standard. The rate of drift is pro-

portional to the frequency error of the 1024 crystal oscillator. If the error is large,

the waveform on scope channel 2 will drift by so rapidly that the waveform will appear

as a blur.

g. Center the 1024 front panel STD ADJ potentiometer by inserting a small blade

screwdriver and turn the potentiometer 20 turns counterclockwise and then back 10

turns clockwise.