u.1.2. Receive Audio Signal Levels
The purpose of these two measurements is to determine the gain of the receive audio
stages associated with V14. This is done by measuring the audio input levels needed to
produce 500 mw audio output into audio level meter or dummy load (500 mw = 2 VAC
across an 8 resistor). Input and output levels can be measured using an AC voltmeter.
a) Disconnect speaker and connect an Audio Level meter to the speaker jack
(alternatively, an 8 load resistor and AC voltmeter can be used to measure the
levels)
v) Using an audio signal generator at 1 KHz, connect the generator to the top of the
AF Gain control and adjust the AF Gain control to provide 500 mw audio output.
Note: In lieu of an audio generator, you can use the built-in calibrator by tuning for a 1
KHz audio beat note (tone) and adjusting the AF Gain control to provide 500 mw audio
output.
Audio Stages: Expected Signal Levels for 500 mw Audio Output
TP Input Signal Injection Point Frequency Expected Level Actual Input
AF Power
Amp
Top of AF Gain Control
Adjust for AF Gain Control to provide
500 mw audio output
1 KHz 3.2 - 3.6 VAC
@ V14 pin 8
Audio Amp Top of AF Gain Control
Adjust for AF Gain Control to provide
500 mw audio output
1 KHz 0.1 VAC
@ V14 pin 1
Table 1. Receive Audio Levels
v.1.1. Receive RF and IF Signal Levels
This procedure measures the nominal signal levels required to produce 2 VAC (audio)
at the top end of the AF Gain control. It requires an AC voltmeter, a signal source with a
calibrated output and a probe with a blocking capacitor. The following figure shows one
possible setup using a calibrated RF source feeding a step attenuator that is used to set
the injection signal level.
By using a 50 test setup, the effects of the circuit related to the signal injection point
are largely swamped out by the test setup.
During this procedure, it is necessary to disable the AVC circuitry to prevent the AVC
circuitry from affecting the gain of the stages being measured.
Initial Test Setup:
RF Gain control fully clockwise
Signal Level Measurements Page 45
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