Operating Instructions— Type 1A1
this is an overlapping area. Apply the reference signal to
Channel 1 and set the oscilloscope Triggering Source switch
to the Plug-In position. Set the Triggering Coupling switch
to the desired AC position. Set the Triggering Coupling
switch to the desired AC position (AC, AC Slow, AC Fast
or AC LF Reject). If your oscilloscope does not have the
Plug-In switch position, apply the signal from the CH 1 TRIG
GER OUT connector to the oscilloscope Trigger Input con
nector and set the Triggering Source switch to Ext.
When triggering on Channel 1, and if one of the signals
changes frequency, the Channel 2 signal will appear to free
run. This phenomenon is useful for determining the zero-beat
points between the two signals.
In high-frequency applications where the bandwidth limit of
the Type 1A1 Channel 1 trigger amplifier is a limiting fac
tor, the reference trigger for the oscilloscope can be derived
from external sources. If derived from the signal applied to
the Type 1A1 from the device under test, consider the loading
effect of the oscilloscope and interconnecting leads on the
signal source. If loading is a factor, use other methods.
For example, if you use a signal generator to drive the de
vice under test, and the generator has a trigger-output con
nector, use the trigger from the generator to externally trigger
the oscilloscope. Or, connect the cable end of an atten
uator probe to the Trigger Input connector on the oscillo
scope and connect the probe tip to the trigger source.
ADD— Algebraic Addition O f Two Signals
In many applications, the desired signal is superimposed
on an undesired signal such as line frequency hum, etc. Al
gebraic addition makes it possible in many cases to im
prove the ratio of desired to undesired signal. To do this,
connect one INPUT to the source containing both the de
sired and undesired signal. Connect the other INPUT to a
source containing only the undesired signal. Place the MODE
switch to the ADD position. Set the PULL FOR INVERT
switches to opposite polarities (depending upon the polarity
of the desired signal). By carefully adjusting (especially at
low frequencies) the VARIABLE VOLTS/CM control of one
of the channels, the undesired display signal can be reduced
by a factor of 20 compared to the amplitude of the desired
signal.
Using the CH 1 SIGNAL OUT Connector
If greater sensitivity is needed to observe low-level sig
nals in a device under test, use Channel 1 as wideband
AC-coupled 10X preamplifier for Channel 2. To do this,
connect a coaxial cable (equipped with suitable connectors)
from the CH 1 SIGNAL OUT connector to the Channel 2
INPUT connector. Set the Channel 1 VOLTS/CM switch to
.005 and the Channel 2 INPUT SELECTOR switch to AC.
Apply the signal to be observed to the Channel 1 INPUT
connector.
NOTE
For optimum bandw idth and transient response,
use the coaxial cable (Tektronix Part No. 012-
0076-00) furnished with the unit. As an a lterna
tive method, use a 3-inch w ire made from No. 18
solid tinned-copper wire.
CAUTION
Do not apply external voltages to either the CH
1 SIGNAL OUT or TRIGGER OUT connectors as this
may damage the internal circuits. Shorting the
connectors to ground, however, w ill not cause any
damage.
The following characteristics and brief operating notes
are provided for your consideration:
1. Bandwidth of Channel 1 and Channel 2 connected in
cascade (Channel 1 and 2 VOLTS/CM switches set to .005)
between 3-dB down points is about 2 Hz to about 15 MHz
(Channel 1 INPUT DC coupled).
2. Output impedance of the Channel 1 preamplifier is
nominally 50 ohms.
3. Channel 1 preamplifier voltage gain is about 10X
when the Channel 1 VOLTS/CM switch is set to .005; 5X
when set to .01; 2V2X when set to .02, and IX when set to
.05.
4. Use the Channel 1 preamplifier as an impedance trans
former with or without voltage gain. With a 1-MO input
and 50-0 output the voltage gain is up to 10. The amount
of voltage gain depends on the Channel 1 VOLTS/CM switch
setting.
5. Maximum input signal that can be applied to Chan
nel 1 with the VOLTS/CM switch set to .005 and the Chan
nel 1 INPUT SELECTOR switch set to AC is about 50 mV to
get full amplification without overdriving the channel. If
the Channel 1 INPUT SELECTOR switch is set to DC and the
Channel 1 POSITION control is centered, ± 2 5 mV is maxi
mum input signal that can be amplified without distortion.
6. During dual-trace operation, the signal in Channel 1
will be presented on the CRT when Channel 1 turns on.
Then, the amplified Channel 1 signal will be displayed on the
CRT when Channel 2 turns on. Thus, Channel 1 can be used
as a monitor for its own signal while it is being applied
to Channel 2.
7. In applications where the flat frequency response of
the Type 1A1/oscilloscope combination is not desired, a
suitable filter inserted between the CH 1 SIGNAL OUT
connector and the Channel 2 INPUT connector will allow
the oscilloscope to essentially take on the frequency re
sponse of the filter, providing the filter frequency response
is within the system bandwidth.
8. Output noise level is approximately 200/.iV, RMS, when
the Channel 1 INPUT SELECTOR switch is set to AC or DC
and no signal is applied to the Channel 1 INPUT connector.
By inserting a frequency selective filter of your own choice
in place of the CH 1 SIGNAL OUT to Channel 2 INPUT
coaxial cable, the noise level can be reduced. For ex
ample, use a 400-hertz filter for observing low-level 400-
hertz signals.
9. AC coupling blocks the no-signal DC level (typically
+0.45 volts) of the Channel 1 Signal Pickoff Amplifier
Q164/Q174 stage so the trace can be positioned on the
CRT. AC coupling is most easily accomplished by setting
the Channel 2 INPUT SELECTOR switch to AC.
10. The MODE switch, Channel 1 POSITION, PULL FOR
INVERT and VARIABLE VOLTS/CM controls do not have any
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