Audio Frequency Response; Eia Standard Rs-152B - Motorola R-2001D Operator's Manual

AUDIO FREQUENCY RESPONSE
1. As shown in figure 4-10, connect the Analyzer's RF In/Out port to the transmitter's RF output and the VertiSinad/
Dist input jack to the Mod Out jack through a BNC tee fitting connected to the transmitter's microphone audio input.
Disable PL and DPL.
2. Select DVM/Dist DISPLAY and set it to mode 1, AC DVM. Set FUNCTION to Monitor FM, attenuator to -40 dB,
MODULATION to Cont and Tone A. Use the keypad to enter the transmitter frequency. Turn off the 1 KHz and Ext
Mod controls.
3. Set DISPLAY to Signaling Sequence. Use the keypad to enter mode 1, AlB encode, Tone A and enter the frequency
to be tested.
4. Set DISPLAY to Gen/Mon Mtr, key the transmitter, and adjust Code Synth Level control to provide 300/0 of rated
transmitter deviation.
5. Change DISPLAY to DVM/Dist. Note both the transmitter MIC Audio input level in dBm and the test frequency, for
later use.
6. Repeat the above procedure, adjusting Code Synth Level to maintain 30% of rated deviation, for each frequency to
be tested.
7. Plot the data points obtained above in db relative to the 1 KHz Level and compare with the transmitter's specifica-
tions. EIA RS-152B specifies that a transmitter's frequency response be within
+
1 or -3 dB of a
+
6 dB per octave
pre-emphasis from 300 to 3000 Hz (6 dB per octave roll-off allowed between 2500 and 3000 Hz). Refer to figure 4-11
below, Frequency Response diagram.
o
db-';"+¥~-----------.,..r;;.'-
-3 db
10.5 db
.5db
300
Hz
1000
Hz
2500 3000
Hz Hz
FIGURE 4-11. AUDIO FREQUENCY RESPONSE; EIA STANDARD RS-152B
4-21