Broadcast Electronics AM-2.5E, User Manual

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2-32
2. Refer to Figure 2-6 and adjust the left channel level control to obtain a horizontal
lissajous pattern (refer to Figure 2-15).
3. Adjust the group delay as follows:
A. Configure the group delay circuitry for adjustment as follows:
1. Refer to Figure 2-6 and configure the left channel 4 microsecond and
8 microsecond sections to in.
2. Refer to Figure 2-6 and operate the left channel delay control fully counter-
clockwise.
B. Refer to Figure 2-6 and adjust the left channel delay control to close the oscillo-
scope display and obtain a straight-line lissajous display as shown in the maxi-
mum left channel separation lissajous pattern (refer to Figure 2-15). If the
display will not close, proceed as follows:
1. Refer to Figure 2-6 and: 1) configure only the 8 microsecond delay section
to in and 2) adjust the left channel delay control to close the oscilloscope
display.
2. If the display will not close refer to Figure 2-6 and: 1) configure only the 4
microsecond delay section to in and 2) adjust the left channel delay control to
close the oscilloscope display.
4. Adjust the separation at 7 kHz as follows:
A. Adjust the audio generator for a 7 kHz left channel output at +10 dBm.
B. Refer to Figure 2-6 and adjust the left channel cutoff and peak controls to
obtain a maximum left channel separation lissajous pattern as shown in
Figure 2-15.
C. If a maximum left channel lissajous pattern can not be obtained, refer to Figure
2-6 and adjust the left channel delay control to close the oscilloscope display
and obtain a straight-line lissajous pattern (refer to Figure 2-15).
5. Repeat the entire procedure for the right channel. Adjust the right channel level,
cutoff, peak, and delay controls as required to obtain optimum separation and
distortion from the right channel.
6. Repeat the entire procedure for equalization circuit 2. Adjust the equalization
circuit 2 using the equalization 2 left/right channel level, cutoff, peak, delay,
controls and the equalization 2 group delay sections to obtain optimum separation
and distortion.
2-148. Once the stereo adjustment is complete: 1) refer to SECTION III, OPERATION and oper
ate the pilot switch on the stereo circuit board to ON and 2) remove the test equipment.
2-149.
SINGLE CHANNEL LEVEL.
The transmitter is equipped with a single channel level con
trol. When the transmitter is operating in the stereo mode, the level control is designed to
boost a remaining audio channel level in the event of a failure in one channel. For trans
mitters operating in the stereo mode, adjust the single channel level control as follows: