Am Modulation Linearity Test; Am Modulation Linearity Test Setup - Motorola R-2001D Operator's Manual

AM MODULATION LINEARITY TEST
1.
Connect the Analyzer's RF In/Out to the output of the Transmitter under test, as shown in figure 4-13.
2. Connect the OSCILLOSCOPE Ext Horiz input connector to the scope probe. Set Horiz control to Ext, DISPLAY to
Gen/Mon Mtr, and set to correct transmitter frequency.
3. Change DlSPLAY to IF and set FUNCTION switch to Monitor. Connect the Analyzer's Mod Out jack to the trans-
mitter's microphone audio input.
4. Connect the scope probe to the secondary of the transmitter modulator stage output transformer.
CAUTION
Do
not
exceed 300 volts maximum to the Analyzer's DVM input.
5. Key the transmitter. Adjust the I KHz Level control to cause the displayed trapezoid figure to come tO'a point at one
end. This corresponds to 100070 AM modulation. If necessary, adjust the horizontal vernier control to make the
display just fill the screen,
6. Observe the resulting trapezoid figure. The top and bottom sides of the trapezoid should be straight. Any curvature
indicates non-linearity in the transmitter final amplifier stages.
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'-----"'
FIGURE 4-13. AM MODULATION LINEARITY TEST SETUP
4-24