1-8
HP 85325A Operating and Service Manual
Installation
Mixer LO Power Level Adjustment
Mixer LO Power Level Adjustment
NOTE
[Brackets]
indicate a front-panel key or a computer key board.
{Braces}
indicate a display softkey selection.
CAUTION
It is critical that you set LO power before connecting the HP 11970 mixers.
Initial Setup
1. If using an HP 8530A, press:
[DOMAIN]
{FREQUENCY}
2. Place the receiver in the single point (CW) mode by pressing:
STIMULUS
[MENU]
,
{SINGLE POINT}
.
3. Press
[CENTER]
and enter the lowest frequency available in your
millimeter band.
Initial Fixed
Attenuator Value
Selections
The internal fixed attenuator value in the reference module is set so the
mixer LO input port is not damaged by excessive power (maximum power
for an HP 11970x is +20 dB). The maximum unleveled power is possible if
the ALC loop of the HP 85309A and reference module is broken.
To check what the maximum unleveled power level is:
1. Disconnect the detector voltage feedback cable at the reference module
while monitoring the power level as shown in Figure 1-4 on page 1-11.
Perform the test within the frequency range of operation.
2. Install an attenuator in the reference module which has a value that
keeps the power level below your mixers damage level. (See Figure 1-2
on page 1-10)
NOTE
The attenuator values shown in Table 1-4 on page 1-9 can be used if
HP 85381A RF cable assemblies are used.
3. Determine the minimum attenuator value for the 85326-60001 (test
module), and the 85326-60002 (reference module) using Table 1-4 on
page 1-9.
