HP (Hewlett-Packard) HP 85660B ユーザーズマニュアル

The 60 MHz low-pass filter rejects unwanted mixing products from the mixer. Q4 and

 amplify and limit the IF signal and give it the proper levels to run the following ECL

circuitry.

The outputs of M and N dividers are compared in 

 When they are in phase, the outputs

of 

 are narrow, coincident pulses. For unlock conditions, the output pulses are of varying

widths.

 and 

 are a low-noise differential pair preamplifier. Their outputs are combined in the

integrating amplifier of 

 and 

 are voltage comparators which compare each tune line to the average plus a

small offset provided by R29. If the loop unlocks, one of the preamplifier outputs is higher
than the comparison voltage, and the phase lock indicator goes high, indicating the unlock
condition.

The 

 M/N Phase Detector mixes the 

 M/N VCO output (355 to 395 MHz) with

400 MHz from the 

 100 MHz VCXO. The product of this mixing and the 20 MHz

reference from the 

 are then divided by the M and N dividers respectively, and their

resultant outputs are compared by a phase/frequency detector. The phase error is used to
tune the 

 VCO.

The two dividers (M and N) are identical in operation and their waveforms can be compared
for troubleshooting purposes. The M and N numbers can be set to the same value and various
test points within each divider compared to reveal a malfunction, providing one of the dividers
is known to be operating properly.

To display the M and N divide numbers on the HP 8566B CRT, key in the following settings:

 

 (KSF)

0 Hz

SWEEP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

The third line of the diagnostic (KSR) should read as follows:

1 20 20

2