TB7100 Service Manual Transmitter Fault Finding (25W) 259
© Tait Electronics Limited October 2005
Task 25 —
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 13.8 (B1 band) or Table 13.9 (H5, H6). (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 C300 (see Figure 13.15). Earth the probe to the
FCL TOP
can adjacent to the PA driver circuitry. The required voltage should
be as given in Table 13.8 (B1 band) or Table 13.9 (H5, H6).
5. Enter the CCTM command 32 to place the radio in receive mode.
6. If the voltage measured above is correct, go to Task 26
. If it is not, go
to Step 7.
7. Check C300 (see Figure 13.15). If C300 is not faulty, go to
“Frequency Synthesizer Fault Finding” on page 143. If C300 is
faulty, replace it and return to Step 2.
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