Service manual

ALIGNMENT AND TEST PROCEDURES
7-13
Month 2000
Part No. 001-2004-601
Receiver TCXO Frequency Adjustment
C R I T I C A L A D J U S T M E N T
The TCXO must be adjusted within 5 minutes of turn-
ing the AC power on to the repeater. Do not under
any circumstances try to set frequency later on in any
of the tests, as TCXO frequency stability cannot then
be guaranteed.
1. Check the receiver injection frequency by using a
"sniffer" pickup loop, or RF probe connected to a
suitable frequency counter placed near L139 in the
Receiver (see Section
7.1.4).
2. Adjust Y201 (TCXO) on the Receiver to within
±50 Hz of the channel frequency + 52.95 MHz.
Receiver Audio Distortion Measurement
1. Adjust the RF generator for 100 µV into the
Receiver with a modulation tone of 1 kHz at ±3 kHz
deviation (25 kHz channels) or ±1.5 kHz deviation
(12.5 kHz channels).
2. On the MAC, insert test cables into J100/J103 and
connect to an AC voltmeter.
3. Adjust R237 for 0 dBm (775 mV RMS).
4. On the MAC, connect a 16 ohm load and distortion
analyzer to J101 or J104.
5. Adjust R236 for 2.8V RMS and measure the distor-
tion. Distortion should be < 3%.
Receiver Hum and Noise Measurement
1. Adjust the RF generator for 100 µV into the
Receiver with a modulation tone of 1 kHz at ±3 kHz
deviation (25 kHz channels) or ±1.5 kHz deviation
(12.5 kHz channels).
2. On the MAC, connect a 16 ohm load and distortion
analyzer to J101 or J104.
3. Adjust R236 for 2.8V RMS.
4. Remove modulation from the RF generator. The
measured level must be ≤ -50 dB.
Receiver SINAD Measurement
1. Adjust the RF generator for 100 µV into the
receiver with a 1 kHz tone at ±3 kHz deviation
(25 kHz channels) or ±1.5 kHz (12.5 kHz channels).
2. On the MAC, connect a 16 ohm load and distortion
analyzer to J101 or J104.
3. Adjust R236 for 2.8V RMS.
4. Re-adjust RF level for 12 dB SINAD.
12 dB SINAD reading should be ≤ 0.35 µV.
Receiver Squelch Adjustment
1. Adjust the RF generator for 100 µV into the
receiver with a 1 kHz tone at ±3 kHz (25 kHz chan
-
nels) or ±1.5 kHz deviation (12.5 kHz channels).
2. On the MAC, connect a 16 ohm load and distortion
analyzer to J101 or J104.
3. Adjust R236 for 2.8V RMS.
4. Set the RF generator output for 5 dB SINAD.
5. On the MAC, adjust R234 so the Receiver just
squelches.
6. Increase the RF generator output until the Receiver
unsquelches. Reading should be
≤ 10 dB SINAD.
Receiver Data Level Adjustment
1. Adjust the RF generator for 100 µV into the
receiver with a 100 Hz tone at ±1 kHz (25 kHz
channels) or ±800 Hz deviation (12.5 kHz
channels).
2. On the MAC, insert test cables into J100/J103 and
connect to an AC voltmeter.
3. Adjust R235 to achieve 340 mV RMS.
Local Speaker/Microphone Check
1. Adjust the RF generator for 100 µV into the
receiver with a 1 kHz tone at ±3 kHz deviation
(25 kHz channels) or ±1.5 kHz (12.5 kHz channels).