PAMS
Technical Documentation
NSC/W–1/3
Disassembly & Troubleshooting Instructions
Page 36
Original 11/99
VHF VCO
The VHF VCO signal is used to generate the transmitter intermediate fre-
quencies. The VHF VCO has two fixed frequencies. The operating frequen-
cy is locked in phase locked loop which is controlled by the baseband
Because the oscillator employs two frequencies it also has two diferent
switching modes. These modes are controlled by the BAND signal. In
AMPS and TDMA800 modes the frequency is 322.38 MHz and the logical
level of the BAND signal is ”HIGH”. In TDMA1900 mode a higher if is needed
and the operating frequency is increased to 392.46 MHz. The BAND signal
is also set to logical level ”zero”
The VHF VCOoutput signal is fed to the PLUSSA LO pin no.8. In the PLUS-
SA the signal is divided for the phase detector and TX elements. Before be-
ing fed to the I/Q–modulator the frequency is divided by 2.
