Service manual

Pre-operational System Testing
70
DCB, DCFCB and DCFCTB Models
DTMF Transmit Level Adjustments (DTMF versions of DCFCTB only)
1. To Transmit and generate a DTMF test tone, apply a jumper across the JP15 on
the FCT controller board, (refer to Figure 3 Communications/Controller Board
Layout on page 24 for details).
2. Confirm the deviation level is at 3.0 kHz (or 1.5 kHz for a 12.5 kHz spaced
channel). This level has been pre-set at the factory, however if adjustment is
required, set R71 on the controller board for the required deviation.
3. Utilizing an in-line Watt meter, confirm that the forward radiated power output
matches the specified power output listed on the final test data sheet supplied
with unit within 20%. Also verify that the VSWR is less than 5%. Refer to the
Installation section if the VSWR is excessive.
FSK Transmit Level Adjustments (Digital FSK versions of DCFCTDB only)
1. To Transmit and generate an FSK modem tone, apply a jumper across the JP15
on the FCT controller board, (refer to Figure 3 Communications/Controller Board
Layout on page 24 for details).
2. Confirm the deviation level is at *3.0 kHz. This level has been pre-set at the
factory; however if adjustment is required, set R70 on the controller board for the
required deviation. If CTCSS is used, set the CTCSS level to 0.75 kHz.
3. Using an in-line Watt meter confirm that the forward radiated power output
matches the specified power output listed on the final test data sheet supplied
with unit within 20%. Also verify that the VSWR is less than 5%. Refer to the
Installation section if the VSWR is excessive.
*Note: Deviation levels are cut in half on 12.5 kHz spaced channels.
Receive Level Adjustments
1. Inject a 100uV carrier signal modulated with a 1 kHz tone at *3.0 kHz deviation
for DTMF systems. Use *3.0 kHz deviation for digital systems.
2. Connect an oscilloscope to TP8 on the controller board and confirm a clean,
undistorted sinewave of 1 V
p-p
. The level has been pre-set at the factory; however,
if adjustment is required, set R48 on the controller board to 1 V
p-p
for the external
transceiver. The level of the on-board receiver module is fixed and does not need
to be adjusted.
*Note: Deviation levels are cut in half on 12.5 kHz spaced channels.
Two-tone and DTMF Controller Decode-ability Testing
1. Unplug JP21 to disable the siren.
2. With the transmit modulation level set to *3 kHz from the communication
monitor inject a 0.5 uV carrier signal.