Lox/Lx (#3 Relay); Lox/Lx (#4 Relay); Attenuator States; Off - Tektronix 11A52 Service Manual

Theory of Operation
lOX/lX (#3 relay)
With the #3 relay in the XlO position (relay not energized), the signal from the #2 relay is attenuated by a
factor of 10. With the #3 relay in the lX position (relay energized), the signal from the #2 relay is not
attenuated and proceeds to the skin-loss network (the resistor/capacitor network between the #3 and #4
relays).
The skin loss network compensates for high-frequency losses in the relays and the two cables connected to the
attenuator.
lOX/lX (#4 relay)
With the #4 relay in the lOX position (relay not energized), the signal from the skin-loss network is attenuated
by a factor of 10. When the #4 relay is set to the lX position (relay energized), the signal from the skin loss
network is not attenuated and proceeds to the attenuator output.
The attenuation factors of the two lOX attenuator networks are correct when the output of the attenuators drive
a 50
.Q
termination (the main amplifiers incorporate 50
.Q
terminations at their inputs).
Attenuator States
DC
This is the most used attenuator state. Here the Cal/Norm relay is set to select the input signal. The AC/DC
relay selects DC and the two lOX/lX relays are set for the required attenuation factors. Whenever lOX
attenuation is required, the #3 relay does the lOX function and the #4 relay is set to lX. (This is because the
attenuator associated with the #3 relay can dissipate more power than that of the the #4 relay.)
Off
In the Off mode the #1 relay selects Cal (disconnects the input signal), the #2 relay selects DC (allows
precharge of the AC coupling capacitor), and both the lOX/lX relays (#3 and #4) are set to lOX attenuation
(lOOX total attenuation).
AC
In the AC mode the #1 relay selects Norm (connects the input signal), the #2 relay selects AC, and the lOX/lX
relays are set for the required attenuation factors.
11A52 Extended Service Manual
2-5