HP 8924E, Assembly

Page: 594 / 640

594
Chapter 14, Diagnostics Descriptions
Description of RF Diagnostics (RFDIAGS3)
N:\mkt\MANUALS\HP8924C\ALR\diagnos.fb
Receiver A30
Refer to
table 72 on page 596
for signal flow of the measurements described in
table 128
.
Table 128 A30 Receiver Tests
Measurement Explanation and Suggestions Measurement Point
Down Converter See figure 72 on page 596 . The internal RF generator
frequency, set to 100 MHz and
−
46 dBm CW, is fed
into the first mixer (where it is downconverted to the
614.3 MHz IF) and the receiver (where it is downcon-
verted to the 114.3 MHz IF). The IF is then fed into
the LO/IF/Demod and then to the spectrum analyzer.
The test is repeated for 500 MHz and 900 MHz. Fail-
ures occurring in this test are inconclusive. Failures
may be due to the receiver’s first mixer, the receiver,
the LO/IF/Demod, or the spectrum analyzer.
Spectrum Analyzercenter fre-
quency
IF Counter See figure 73 on page 597 . The internal RF generator
is set to 100 MHz CW and fed into the receiver’s
input. The IF frequency is measured by the IF
counter. The IF chain must operate properly through
the FM demodulator for this test to pass. (If the spec-
trum analyzer option is not installed, this becomes the
first test.)
Counter:REC_IF_COUNT
FM See figure 74 on page 598 . The internal RF generator
is set for FM at 10 kHz peak deviation and a 1 kHz
rate. The peak deviation is measured by the receiver.
This is the first test in which the internal audio source
is applied to the signal generator synthesizer’s FM
modulator. If all the Audio Diagnostics run with no
failures but this and/or the next test fails, check the
path of the audio source from the output of the Modu-
lation Select Multiplexer switch on the A34 Modula-
tion Distribution assembly to the A24 Signal
Generator Synthesizer’s input.
DVM:POS_PK_DET
FM Inverted See figure 74 on page 598 . Same as previous test
except the demodulated FM is inverted.
DVM:POS_PK_DET