HP 8568B manual 27

				1. Center Frequency Readout Accuracy Test
Note		Spectrum analyzer	center frequency readout can fall outside					of
		specified limits if 10 MHz frequency reference has not been calibrated
		within the past year. To eliminate “frequency reference error x
		tune frequency” term, substitute spectrum analyzer 10 MHz FREQ
		REFERENCE rear panel output for frequency standard and repeat
		test.
		‘Ihble 2-2. Center Frequency Readout Error Test Record
		I	Spectrum Analyzer
							Center Readout
	[FREQUENCYSPAN)I(CENTER		FREQumcy~
			(MHz)\I				(MHZ)\I
						Min	Measured	Max
	100 MHz		100		98			102
	100 MHz		500		498			502
	100 MHz		1000		998			1002
	10 MHz		100		99.8			100.2
	10 MHz		500		499.8			500.2
	10 MHz		1000		999.8			1000.2
	10 MHz		1500		1499.8			1500.2
	1 MHz		1000		999.98			1000.02
	100 kHz		1000		999.998			1000.002
	10 kHz		1000		999.9998			1000.0002

Performance Tests 2 - 5