HP 8340B Manual page 182

YO TUNE. Phase-locks
the YO. Coarse error
correction and
AC
noise >
100 Hz are performed by YO
TUNE
(via
the
ASS YO driver and YO main
coil).
The YO frequency
is related to the
M/N output frequency and the 20-30 MHz
reference loop frequency
in the following way:
FYO
=
(N)(FM/N)
-
FSO-SO
Where:
FYO
=°
YO output frequency (MHz)
N
=
N
number input
to the
M/N Loop (harmonic near the frequency to which the
YO
loop
is
tuned)
FM/N
=
MfN
'Q0? output frequency
(MHz)
Fgo-ao
=
20-30
loop output frequency
(MHz) (the 20-30
frequency can be changed
in 1 Hz
steps)
The YO TUNE
output from the
A49 YO loop phase detector
board goes to the
ASS YO driver where it is
summed with the
PRETUNE voltage from the AS4 YO pretune/delay compensation assembly. This
sum
is applied to the
YO
main coil.
FM Coil Drive. This signal provides >100 Hz AC error correction to the YO. The YO FM
coil drive
from
the A49 YO loop phase detector assembly goes
to to
the A44A1
YO
bias
assembly and then to the YO
FM
coil.
A50 YO Loop Interconnect Assembly Theory of Operation
The
ASO YO loop interconnect assembly distributes power and signals to the A48 YO sampler
assem¬
bly,
the A49 YO phase detector, and the A44A1 YO bias assembly.
It
also contains the following
signals, each of which
is
provided with
a
test point.
TP2 LOMD
low
=
FM
overmodulation
is
occurring.
TP4 HFIL high
=
The YIG
Oscillator
CW
filter
is
engaged.
TPS HLEY high
=
The
YIG Oscillator loop phase-lock
is
enabled.
TP7 HULY high
=
The YIG
Oscillator loop is
not phase-locked.
The test points serve two purposes:
•
Each test point can be used to monitor the
state of the
digital signal (The level
will be somewhat
less than the actual signal level
due
to the resistors on each side of the test points).
•
The test
point can also be used to force
a
logic condition to occur by connecting
it
to
+SV
or
ground.
Test
points
are provided on the YO loop interconnect assembly for each supply voltage
and for
the
YO
coil
voltage.
The ASO YO
loop interconnect assembly isolates and separately filters supplies going to different
portions of the YO loop assembly.
D-12
Sweep Generator
-
YO
Loop Theory
of
Operation
HP 8340B/41B