7.
Set the spectrum analyzer to the following settings:
Center frequency .............................................
..300MH
z
Span ............................................................. OHz
Trigger .................................................. SINGLE,EXT
a.
b.
C.
d.
e.
f.
g.
h.
i.
j.
k.
On the spectrum analyzer, press (SAVE),
S.&m
STAlZ
, STAm 0 .
Remove jumper A14J23 and connect a dc voltage source to A14J23 pin 2. Connect the
voltage source ground to A14J23 pin 3.
Connect a microwave frequency-counter or another spectrum analyzer to the spectrum
analyzer first LO OUTPUT (front panel output).
Set the dc-voltage source output for 0 Vdc and note the 1st LO frequency.
Set the dc-voltage source output for
+lO
Vdc. The first LO frequency should
momentarily increase approximately
+15.6
MHz.
The voltage at A14U332 pin 2 should be approximately 19% of the voltage at A14J23
pin 2.
If the first LO frequency did not change in step e, press
ILINE)
to turn spectrum analyzer
off and disconnect
WlO
from A14J3.
Place a jumper between A14J3 pins 9 and 10. Place a 50
St,
3 watt resistor across
A14J3 pins 5 and 6 (resistor, HP part number 0811-1086). Press
(LINEI
to turn spectrum
analyzer on.
On the spectrum analyzer, press
(E),
STAm
, STATE 0 .
If the voltage at U332 pin 2 is correct with A14J3 pins 9 and 10 shorted, but was
incorrect with WlO connected, the YTO FM coil is probably open; replace the
All YTO.
Replace jumper A14J23.
Fractional N Span
Problems
(LO Spans 52 MHz)If the fractional N spans are inaccurate or non-existent, but the fractional N PLL is locked to
the correct frequency and other spans are correct, there may be a problem with the HSCAN
signal. Check that HSCAN is present at the fractional divider, U113 pin 41 in function block
AS. HSCAN comes from the A3 interface assembly and goes to the sweep generator circuitry
in function block A and to fractional N.
Synthesizer Section 1 l-39