HP (Hewlett-Packard) 24A Benutzerhandbuch

Uncoupled operation applies to Option 001 synthesizers only.

Uncoupled operation is useful when working with mixers. Figure 1-16
shows a hypothetical setup where the synthesizer is providing
a small signal to a mixer. The synthesizer output is -8 
which in Leveling Node 

 results in 

   0 

ALC Level = -8 

 The mixer is driven with an LO of 

 

and has LO to RF isolation of 15 

 The resulting LO feedthrough

of -5 

 enters the synthesizer’s OUTPUT port, goes through

the attenuator with no loss, and arrives at the internal detector.
Depending on frequency, it is possible for most of this energy to enter
the detector. Since the detector responds to its total input power
regardless of frequency, this excess energy causes the leveling circuit
to reduce its output. In this example the reverse power is actually

larger than the ALC level, which may result in the synthesizer output
being shut off.

Figure 1-17 shows the same setup, with uncoupled operation used to
produce the same -8 

 output. In this case, 

 = -10 

ALC Level = 

 

 The ALC level is 10 

 higher, and the

attenuator reduces the LO feedthrough by 10 

 Thus the detector

sees a 

 

 desired signal versus a possible -15 

 undesired

signal. This 17 

 difference results in a maximum 0.1 shift in the

synthesizer output level. To set the synthesizer to the attenuator
uncoupled mode as discussed in this example, do the following:

.

1. Press POWER 

2. Select 

 and press 

 

 

 This step does two

things, it uncouples the attenuator from the rest of the ALC
system, and it lets you set an attenuator value, in this case, 10 

3. Press 

 

 

 

 This sets the ALC level to

 

For more information on the ALC or setting power level, refer to

 

or 

 

 

in Chapter 2.