HP 8340B Manual page 275

5-14.
UNLEVELED RF OUTPUT ADJUSTMENTS (Cont'd)
Remove jumpers
A28W1 and A28W2 if
they are installed
on
the A28 assembly. These jumpers
must be removed to
set the V/QHz
circuit to 0.5V/GHz.
6.
If the A26 assembly has been replaced, preset
the following pots to the position stated (see Figure
5-41):
Set
the following fully clockwise:
A26R88 (MO)
Center
the
following:
A26R7(BAL) A26R43
(HET)
A26R45
(X1) A26R47 (X2)
A26R49 (X3) A26R51 (X4)
A26R91 (GAIN)
0.5
V/GHZ ADJUSTMENT
7.
On the
DUT, press [CW] [1] [0] [MHz]. Adjust A28R67 (V/GHz)
for
a
DVM
indication
of
5
mV +
0.5
mV.
SYTM TRACKING AND UNLEVELED SRD BIAS ADJUSTMENTS
8.
On the OUT,
press the following key sequence:
[START
FREQ]
[6]
[.]
[9] [GHz]
[STOP FREQ] [1] [3]
[.]
[5] [GHz]
[POWER LEVEL] [0] [dBm]
[SWEEPTIME] [2] [0] [0] [msec]
[XTAL]
[SAVE] [1]
9.
Connect
the oscilloscope and detector as shown
in
Figure 5-40. Set the oscilloscope
to
A
vs
B
mode, horizontal sensitivity (CHAN B) to
1
V/Div
dc,
and
vertical sensitivity
(CHAN
A) to 0.05
V/Div
dc. Adjust the horizontal and vertical position controls to
view the entire swept RF output
response on
the oscilloscope. Readjust the vertical sensitivity
if necessary so that the trace
covers the maximum number of divisions possible.
Band
2
Adjustments
10.
Adjust
A28R82 (GAIN) to peak the power across the entire band (readjust the scope's vertical
position and/or
sensitivity if
necessary).
NOTE
In
the following adjustments, turning the X2A/B, X3A/B, or X4A/B
con¬
trols clockwise when in
the appropriate band will increase the
SRD bias
and be closer to the squegging region'.
If
squegging
occurs, turn the
above controls counter-clockwise
until
the RF output power
is
reduced
=
0.5 dB below the squegging region.
1 The
squegging region Is an area where undesired
oscillations of the YIG sphere or Step Recovery Diode
(both Internal to
the SYTM) are
produced.
Symptoms of squegging are
power
reversal (actual
RF
output power decreases as
selected RF output
power
is
increased), power
holes In
the RF output, and spurious responses on the RF output
5-76 Adjustments
HP 8340B/41B