Ericsson LBI-31511B, Maintenance Manual, Page: 11 / 18

TRANSMITTER ALIGNMENT
SYNTHESIZER & TRANSMITTER ALIGNMENT
EXCITER TRANSMITTER POWER AMPLIFIER
Preset all four tuning screws in the exciter (C8-C11) so that the tops of the tuning screws are approximately 7 mm above
the top of the casting.
Preset L103 so that the core is flush with the top of the coil form.
NOTE
The exciter can be isolated from the rest of the radio for tuning purposes, if desired. To isolate and set up, remove P102
and P103. Connect a (0-1 watt) wattmeter to J103-2, 4. Apply a +7 dBm at 1/3 carrier frequency signal to J102-2, 4.
If less than 6.0 MHz (5.0 MHz on 403-430 MHz split) channel spacing is required, select the highest transmit RF frequency.
If 6.0 to 12.0 MHz bandwidth (5.0 to 10.0 MHz on 403-430 MHz split) is required, select center frequency. (Refer to "Accessing
Center Tune Frequency" and complete steps.
STEP
METERING POSITION
TUNING
CONTROL
METER
READING
PROCEDURE
GE TEST
SET
MULTIMETER
(- TO A-)
1. LED D713 L209 Light out Select the highest frequency transmit channel. Key the transmitter and
tune L209 so that the lock detect indicator D713 goes out.
2. J202 L209 Below 7.5
Vdc Monitor J202 with a digital voltmeter. Tune L209 for 7.5 Vdc max.
3. LED D713 C220 Light out Unkey the transmitter. Select the highest frequency receive channel and
tune C220 so that the lock detect indicator D713 goes out.
4. J202 C220 Below 7.5
Vdc Monitor J202 with a digital voltmeter. Tune C220 for 7.5 Vdc max.
5. J202 Above 3.0
Vdc Select the lowest frequency transmit and receive channel. Key the
transmitter and check the TX VCO voltage. Unkey the transmitter and
check the RX VCO voltage. Both readings should be above 3.0 Vdc.
Test aid for TX and RX Injection Monitor TX injection at J102 and RX injection at J451. (Note:
Terminate TX VCO output with 50 ohms to maintain lock with plug
removed).
TX inj5 to +15 dBm
RX inj5 to +15 dBm
STEP
METERING POSITION
TUNING
CONTROL
METER
READING
PROCEDURE
GE TEST
SET
MULTIMETER
(- TO A-)
6. A
(AMPL-1)
J101-10 0.25 V Key the transmitter. No tuning required in this step.
7. B
(TRIPLER)
J101-9 L103 -0.45 V Tune L103 for maximum negative meter reading (switch voltmeter for
negative reading.)
8. B
(TRIPLER)
J101-9 C8 -0.5 V Tune C8 for maximum meter reading.
9. C
(AMPL-3)
J101-8 C9 2.0 V Tune C9 for maximum meter reading. Stop when maximum is reached.
EXCITER/TRANSMITTER POWER AMPLIFIER (Cont.)
*
Fo is the transmit output frequency at the antenna. The injection frequency is Fo/3 at J102.
REFERENCE OSCILLATOR FREQUENCY
STEP
METERING POSITION
TUNING
CONTROL
METER
READING
PROCEDURE
GE TEST
SET
MULTIMETER
(- TO A-)
10. C
(AMPL-3)
J101-8 C10 0.01 Tune C10 for a dip, 0.01 volts typical. Note, after C11 is tuned, this voltage
typically will be 0.5 volts.
11. C11 500 mw Tune C11 for maximum exciter power output as indicated on the wattmeter,
connected to J103-2, 4. Exciter output is typically 600 mw.
12. A
(PA
INPUT)
J1-10 C11 Rated
Output
Power Check exciter power output at both ends of the frequency spread. It should
be equal to or greater than 500 mw. If wattmeter to measure exciter power
is unavailable and the exciter is already connected to the PA, connect the
meter to PA board J1. Connect a 150 watt wattmeter to antenna connector
J2. Set the RF Power Adjust control for maximum power (fully clockwise).
Tune C11 for maximum meter reading on J1, position A. Check the meter
reading at both ends of the frequency spread. They should be approximately
equal. If not adjust C11 accordingly. Set RF power Adjust for rated output
power.
NOTE
If more than 6.0 MHz (5.0 MHz on 403-430 MHz split) channel spacing is
required. Perform steps 13 and 14.
13. A
(PA
INPUT)
J1-10 C11 Select the highest frequency channel. Key transmitter and adjust C11 so that
output power is slightly above rated power.
14. C10 Select lowest frequency channel. Key transmitter and adjust C10 so that
output power is slightly above rated power. Switch to highest frequency
channel and verify rated output power. If necessary repeat this step.
STEP
METERING POSITION
TUNING
CONTROL
METER
READING
PROCEDURE
GE TEST
SET
MULTIMETER
(- TO A-)
NOTE
This step assumes the frequency is measured when the transmitter is first
keyed. If delayed the rapidly rising ambient temperature must be taken into
consideration. Figures 4 and 5 below show the temperature versus
frequency correction curve for the 5 PPM and optional 2 PPM reference
osc.
15. J2 L352 C h a n n e l
O p e ra t in g
Frequency Key the transmitter while monitoring the frequency at the antenna
connector J2.
Adjust L352 for the assigned channel freq.
±
225 Hz for a 5 PPM radio (standard) or
±
90 Hz for a 2 PPM radio (optional).
Note: The receiver injection frequency will automatically be correct.
LBI-31511 LBI-31511
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