Receive Vco And Related Circuitry (Uhf Radios) - Tait TM9100 Service Manual

9.5

Receive VCO and Related Circuitry (UHF Radios)

If there is no fault with the power supplies, the PLL inputs and output, and
Introduction
the loop filter, check the VCO and related circuitry. The procedures in this
section apply only to UHF radios with a lock error or receive fault, and
therefore with suspect receive VCO and related circuitry. (The minimum
and maximum receive frequencies for the different UHF frequency bands
are defined in
The measurement points for diagnosing faults in the VCO and related
circuitry are summarized in
Table 9.2 Minimum and maximum receive frequencies for the different UHF frequency bands
Frequency band
H5
H6
192 Frequency Synthesizer Fault Finding
Table 9.2.) There are six aspects:
Task 17: check receive VCO
Task 18: repair PLL feedback
Task 19: repair receive VCO
Task 20: check switching to receive mode
Task 21: repair switching network
Task 22: check receive buffer amplifier
Receive frequency in MHz
Minimum
337 ± 5
378 ± 5
Figure 9.8.
Maximum
441 ± 5
498 ± 5
© Tait Electronics Limited August 2005
TM9100 Service Manual