TB7100 Service Manual Transmitter Fault Finding (50W/40W) 321
© Tait Electronics Limited October 2005
Task 26 —
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 C300.
1. For test purposes select a representative power level and frequency
from Table 14.8 (B1 band), Table 14.9 (H5) or Table 14.10 (H7).
(Note that the data for these tables were obtained using an
RFP5401A RF probe.)
2. To set the power level, enter the CCTM command 326 x, where x
defines the level. To set the frequency, enter the CCTM command
101 x x 0, where x is the frequency in hertz.
3. Enter the CCTM command 33 to place the radio in transmit mode.
4. Use an RFP5401A RF probe or the equivalent to measure the RF
voltage after C3500 (see Figure 14.21 and Figure 14.22). Earth the
probe to the
FCL TOP can adjacent to the PA driver circuitry.
The required voltage should be as given in Table 14.8 (B1 band),
Table 14.9 (H5) or Table 14.10 (H7).
5. Enter the CCTM command 32 to place the radio in receive mode.
6. If the voltage measured above is correct, go to Task 27
. If it is not, go
to Step 7.
7. Check C3500 (see Figure 14.21 and Figure 14.22). If C3500 is not
faulty, go to “Frequency Synthesizer Fault Finding” on page 143.
If C3500 is faulty, replace it and return to Step 2.
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