Tait TP9100 - Page 240

240 Transmitter Fault Finding TP9100 Service Manual
© Tait Electronics Limited May 2005
Task 18 —
Output of
Frequency
Synthesizer
The first point to check in the initial RF signal path is the output SYN TX LO
from the frequency synthesizer. This signal is input to the exciter at C138
(B1 band) or C125 (H5, H6).
1. For test purposes select a representative power level and frequency
from Table 10.6 (B1), Table 10.7 (H5), or Table 10.8 (H6). Note
that the data for these tables was obtained using an RFP5401A RF
probe
2. To set the power level, enter the CCTM command 326 x, where x
defines the level.
3. To set the frequency, enter the CCTM command 101 x x 0, where x
is the frequency in hertz.
4. Enter the CCTM command 33 to place the radio in transmit mode.
5. Use an RFP5401A RF probe or the equivalent to measure the RF
voltage before C138 (B1 band) or C125 (H5, H6) at the
SYN TX LO
measuring via (see Figure 10.8). The required voltage should be as
given in Table 10.6 (B1), Table 10.7 (H5), or Table 10.8 (H6).
6. Enter the CCTM command 32 to place the radio in receive mode.
7. If the voltage measured above is correct, go to Tas k 19
. If it is not, go
to Step 8.
8. Check C138 (B1 band) or C125 (H5, H6) (see Figure 10.10).
If the capacitor is not faulty, go to “Frequency Synthesizer
Fault Finding” on page 159. If the capacitor is faulty, replace it and
return to Step 2.
Table 10.6 RF voltages along the initial RF signal path (B1 band)
Power level
(W)
Frequency
(MHz)
RF voltages (V)
Synthesizer
output
Exciter
output
Driver
output
1 136
155
174
0.47 ± 0.1
0.45 ± 0.1
0.36 ± 0.1
1.8 ±0.3
1.8 ±0.3
1.6 ±0.3
0.43 ±0.3
0.43 ±0.3
0.46 ±0.3
2 136
155
174
0.47 ± 0.1
0.45 ± 0.1
0.36 ± 0.1
1.8 ±0.3
1.8 ±0.3
1.6 ±0.3
0.70 ±0.3
0.66 ±0.3
0.71 ±0.3
3 136
155
174
0.47 ± 0.1
0.45 ± 0.1
0.36 ± 0.1
1.8 ±0.3
1.8 ±0.3
1.6 ±0.3
0.92 ±0.3
1.0 ±0.3
0.96 ±0.3
5 136
155
174
0.47 ± 0.1
0.45 ± 0.1
0.36 ± 0.1
1.8 ±0.3
1.8 ±0.3
1.6 ±0.3
1.4 ±0.3
1.3 ±0.3
1.6 ±0.3