Filser Electronic GmbH
Gewerbestraße 2
ATR 720 C Communications Transceiver
86875 Waal
page 9
2.2.1 Electrical Bench Test
Test Equipment Recommended
1.
VHF Signal Generator: HP Model 608D or equivalent.
2.
RF Power Wattmeter: Bird Truline Model 43 or equivalent.
3.
Regulated DC Supply with 12 to 15 Vdx at 2 amperes capability.
4.
Frequency Counter: HP Model 5383 A or equivalent.
5.
Oscilloscope: National VP 5510 A or equivalent
6
Speaker Load Box: with 4 watt capability.
7.
watt pad, 20dB, 20W
8.
Audio-Detector: Texscan Model DC-50 or equivalent.
9.
Low Impedance microphone that will be used in the aircraft.
2.2.1.1 Test Procedure
1. Connect the Comm Unit into the test set-up, diagramed in Figure 2-1, and set the DC supply
for 13,75 VDC.
2. Connect the VHF signal generator to J 5001, set the generator output level to 1.5 µV with 30 %
- 1 kHz modulation.
3. Set the COMM VOLUME CONTROL for a 100 mw reading on the speaker load box meter.
4. Remove the modulation, look for a 6 dB change on the speaker load box meter.
5. Disconnect the signal generator. Connect the RF wattmeter and frequency counter as dia-
gramed in Figure 2-1.
6. Connect the wattmeter to J 5001. Key the transmitter and talk into the microphone. The watt-
meter indicator should react with a wiggle.
7. With the transmitter keyed, use the frequency counter to check the Unit’s frequency program-
ming. Check all kHz steps from 118.000 MHz to 118.975 MHz and all MHz steps form 118.000
MHz to 135.000 MHz.
8. Check by switching the memory preselector if the four memories are preselected. The Fre-
quency display shows 100.00 MHz when the memory battery is unserviceable or empty. In this
case all four preselected channels will be cleared by switching off the radio.
2.2.2 Microphone Adjustment
It is recommended that the microphone adjustment (see Figure 2-2 ) be performed while the Unit
is on the bench using the aircraft’s microphone(s). This adjustment can be made in the aircraft,
however, it would require removal and insertion of the unit since the MIKE SELECTOR is located
on the side of the chassis. Should the aircraft be equipped with more than one microphone, the
type of microphones should be identical.
Adjustment:
1.Dynamic Microphone
Using a low impedance dynamic microphone (200 ohms) turn the microphone gain trim-
potentiometer R 3104 full
- clockwise -
Note: This position is preset by the manufacturer
