Flatness Compensation Control - HP 8560E Service Manual

RF Section
A15 RF Assembly
7. Move the A2 controller assembly WR PROT/WR ENA jumper to the
8. While measuring the signal at the mixer 10.7 MHz IF output, adjust
9. On the HP 8560E/EC, press
10.Connect the other spectrum analyzer to A15J601 and measure the
11.Enter 4095 into the HP 8560E/EC Flatness Data. The signal level at
12.Check that the gain stages are properly biased and functioning.
13.Check the attenuator stages and flatness compensation control
As long as the flatness data just entered is not stored, the
CAUTION
previously-stored flatness data will be present after the power is cycled.
14.Move the WR PROT/WR ENA jumper on the A2 controller assembly
15.Reconnect the cable to A15J801.

Flatness Compensation Control

Refer to function block G on A15 RF Section schematic in the
E-Series Spectrum Analyzer Component Level Informatio
The flatness compensation control consists of a buffer amp (U909C) and
two identical voltage-to-current converters (U909B and U909D). The
thermistor RT901 in the buffer amp provides temperature
compensation for the PIN diodes in the gain stages and the SAW filters.
600
level should be approximately −22 dBm.
WR ENA position.
the signal source until the level of the 10.7 MHz IF is −40 dBm.
and . Increase the gain of the flatness compensation
FLATNESS
amplifiers to maximum by entering 0 using the data keys. This sets
the gains in the flatness compensation amplifiers to their maximum
values.
10.7 MHz IF signal level. The signal should measure greater than
−10 dBm. If the signal level is incorrect, continue with step 13.
A15J601 should measure less than −36 dBm. This sets the gain of
flatness compensation amplifiers to a minimum. If the signal level is
incorrect, continue with step 13.
circuitry.
a. For minimum gain (flatness data equals 4095), RF GAIN
(A15U909 pin 10) should be at −1.6 Vdc and the current through
each section as measured across R667 or R668 should be about 7
mA.
b. For maximum gain (flatness data equals 0), RF GAIN (A15U909
pin 10) should be at approximately 0 Vdc and the current through
each attenuator section should be close to 0 mA.
to the WR PROT position.
, ,
SGL SWP CAL IF ADJ OFF
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HP 8560
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Chapter 11