HP 8753E - Page 460

The full low band is produced in two sub sweeps, to allow addition IF sltering
below 3 MHz. At the transition between subsweeps, the source is pretuned
and then relocks. ‘Ihble 12-2 lists the low band subsweep frequencies at the
fractional-N VCO and the RF output.
‘able 12-Z. Low Band Subsweep Frequencies
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12-18 TheoryofOperation