10.6952 Mhz Vcxo; Input Switch; Lo Switch - HP 8560A Service Manual

(
f. Press
FREQUENCY SPAN
right-side up. Ignore any "wings" to the left and right of the passband.
g. The amplitude at 4.5 kHz and 5.1 kHz relative to 4.8 kHz should be 0 to -2.5 dB..

10.6952 MHz VCXO

Refer to function block E of A4 Log Amplifier Schematic Diagram (sheet 2 of 4) in the
HP 856OA/61B/63A Spectrum Analyzer Component Level Information
The purpose of the 10.6952 MHz voltage-controlled crystal oscillator (VCXO) is to provide an
LO for down-converting the peak of the 10.7 MHz IF filter's passband to 4.8 kHz. Since the
peak of the passband of the 10.7 MHz IF filters is 10.7 MHz f10 Hz, the frequency of the
VCXO is between 10.69519 MHz and 10.69521 MHz. This frequency can best be measured at
the collector of A4Q202.
The center frequency of the 300 Hz resolution-bandwidth filters and the 10 Hz to 100 Hz
filters should differ no more than 10 Hz. If the center frequency is different by more than this,
or if no signal is present in the 10 Hz to 100 Hz resolution-bandwidth settings, troubleshoot
the 10.6952 MHz VCXO.
Error message 539 may occur if the VCXO is not oscillating. If problems exist with the
VCXO control voltage, error messages 536 or 530 may occur.
Between sweeps the VCXO, at times, is turned off. To prevent the oscillator from turning off,
press (PRESET), (FREQUENCY), 0.3 (GHz), (SPAN), 1 (kHz), [GiYG).

Input Switch

Refer to function block D of A4 Log Amplifier Schematic Diagram (sheet 2 of 4) in the
HP 856OA/61B/63A Spectrum Analyzer Component Level Information
The input switch switches between Log and Linear modes. in addition it contains a 20 dB
attenuator which is used only and always in digital resolution bandwidth settings. CR207,
CR208, and CR209 form the input switch. CR205 and CR206 switch in R234 when in linear
mode to maintain a constant impedance at J3. CR210, CR211, CR212, and CR221 switch the
20 dB attenuator in and out.

LO Switch

Refer to function block F of A4 Log Amplifier Schematic Diagram (sheet 2 of 4) in the
HP 856OA/61B/63A Spectrum Analyzer Component Level Information
The LO switch switches the limiter input between the 10.7 MHz path or the 10.6952 MHz
VCXO path.
),
2 @). The response should now be displayed
binder.
binder.
binder.
IF Section 8-19