HP 8340b User Manual

c.
If
the
instrument
continues
to
fail
the
phase
noise
test,
the
problem
is
most
likely
the
M/N
VCO.
3.
If
the
instrument
failed the
phase noise
test
at
offset
frequencies
greater
than
50
KHz,
the
problem
is
most
likely
the
YO
Loop.
Spurious
Response
This
procedure
assumes
that
the
instrument
failed the
Spurious
Response
test
in
Section
IV. Spu¬
rious
responses can
be
divided
into
Four
categories:
Harmonics/Sub-harmonics
The
HP
8340B/41B
is
essentially three instruments
In
one:
1.
A
heterodyning
(low
band)
source
2.
An
unmodified
YIG
oscillator
source
(band 1)
3.
A
synthesized
source
(full
band
sweep).
In
low
band
(10
MHz
to
2.3
GHz),
the
2.3
to
7.0
GHz
YO
output
is
mixed
with
a
fixed
3.7
GHz oscillator
to
produce
the
RF
frequency.
In
high
band,
the
YO
output
Is
used
directly
or
multiplied
(by
the
band
number)
to
produce
the
RF
frequency.
In
high
band,
the
SYTM
is
designed
to
pass
only
the
RF
output
frequency
and
reject
all
other
frequen¬
cies.
In
low
band,
the
output
of
the
low
band
mixer passes
directly
through
the
SYTM.
To
troubleshoot
for harmonics
and
sub-harmonics
in
low
band
(10
MHz to
2.3
GHz),
use
a
spectrum
analyzer
and
troubleshoot
the
low
band
circuitry.
If
the
instrument
does
not
meet
its
harmonic/sub-harmonic
specification
in
high
band,
suspect
the
SYTM.
Line
Related
Side
Bands
Line
related
spurs
result
when
magnetic
radiation
from
the
power
transformer
is
coupled into
the
M/N
loop,
the
reference
oscillator,
or
the
SYTM.
The amplitude of
a
line
related
spur
coupled
into
the M/N
loop
is
greatest
at
6.9
GHz
(maximum
M/N
loop
frequency);
the
amplitude
of
a
line
related
spur
coupled
into
the SYTM
is
greatest
at
2.3
GHz
(minimum
SYTM
drive
current).
An
increase
in
line
voltage,
or
the
line
voltage selector
PC
can
incorrectly
installed
can
increase
the
radiation
and,
consequently,
the
spur
amplitude.
1.
Check the
waveform on
the
unregulated
power
supplies.
These
supplies have full-wave
bridge
rectifiers.
If
one
diode
is
open,
the
supply
operates
similar
to
a
half-wave
rectifier.
The
output
of
the
regulated
supplies
can
be
normal,
but
the
transformer
current
is
unbalanced,
and
the
magnetic
radiation
can
increase.
Magnetic
radiation
coupled
into
the
M/N
Loop
can
sometimes
be
reduced
by
replacing
A29U1
(The
amplifier limiter
on
the
reference
phase
detector
assembly).
A-46
Assembly-Level
Service Overall Instrument
Troubleshooting
HP
8340B/41B

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English