Technical data

2-4 Service Guide 85309-90082
Operating Information LO/IF Distribution Unit
85309B Front Panel Features 85309B
LO POWER OUT OF RANGE
When lit, this LED indicates that the LO source is not supplying the amount of LO power requested by the LO
POWER ADJUST control.
The LO POWER OUT OF RANGE circuit compares the LO POWER ADJUST setting with the voltage coming
back from the reference detector. The amount of expected detector voltage varies depending on the LO
POWER ADJUST setting. Normally the detector voltage is within the expected range, and the LED is not lit.
However, if anything interrupts the ALC loop, or a relatively low detector voltage is measured, the LED is lit.
(The circuit activates the light if the detector voltage is not within 25% of the expected voltage.) If the LED is
lit, the cause may be one or more of the following:
• The LO source is not set to output a sufficient amount of power. To remedy this, increase power output (if
possible). Make sure your LO source can generate sufficient power at the maximum LO frequency.
• The LO POWER ADJUST is not set properly on the 85309B. Refer to “Step 6. Adjust the LO Power” on
page 1-10 for instructions.
• The LO source's RF OUTPUT is not connected to the 85309B, or the LO source is turned off. This can also
happen if the LO source is on, but its RF output is turned off.
• The LO source is not able to supply the requested amount of power in the measurement frequency
range. Make sure your LO source is specified to produce enough power in the desired frequency range. If
the LO cannot produce enough power at high frequencies, the LO POWER OUT OF RANGE LED will be lit
during the high-frequency portion of the measurement. During this time LO power will not be correct.
• The reference mixer is not connected to the REFERENCE LO OUTPUT of the 85309B (in other words, the
reference mixer is not getting sufficient LO power).
• The reference mixer's Detector Voltage output is not connected to the 85309B.
• There is a failure of the 85309B's ALC circuitry. An ALC failure will usually cause the LED to be lit
permanently, even though all equipment is connected properly.
BAND SELECTION (Option 40x Only)
The Band Selection knob on the front panel of the 85309B Option 400/401/402 models allows the user to
switch between the low band, high band, and external selections. The Band Selection switch positions are:
• LOW 0.1 GHz to 1 GHz operating frequency.
• HIGH 0.3 GHz to 18 GHz operating frequency.
• EXT Enables external control of band selection via rear panel J15 HIGH/LOW BAND SELECT port. TTL
high (+5 V) selects HIGH band; TTL low (0 V) selects LOW band.
NOTE Use Keysight 85320A/B Option H20 external mixer modules to utilize the 0.1 GHz to 3 GHz
frequency range of operation.
If the green LED above the Band Selection knob is lit, the HIGH band is selected. If the LED is not lit, the
LOW band is selected.