NGT—Technical description (2011/2012)
116 NGT Transceiver System Technical Service Manual
Receive path
Input low-pass filters
The receiver input signal goes through one of seven relay-selected LPFs K1 to K7. The
signal then goes via the transmit/receive relay K8 and signal-clamping diodes D3 to D9
to connector J1.
Broadcast filter and RF amplifier
The signal goes through a broadcast filter to reduce any very strong broadcast
frequencies below 1.6 MHz, and then goes to the RF amplifier V101. V101 has a
nominal gain of 9 dB.
When there are very strong signals present, V101 is not required and may be switched
off via the handset using the Cfg RF Pre-Amp entry in the Control List. When this
occurs, a 10 dB attenuator pad is switched by relay K101 to reduce the signal going to
mixer RxMIX1. The signal then passes through a 30 MHz LPF to remove signals above
30 MHz.
First mixer
The balanced mixer, formed by V103, V104, V105 and V106, mixes the received signal
with the local oscillator LO1+, LO1– (VCO). LO1 is buffered by V107 and V108 to
produce an IF of 45 MHz. The mixer has a conversion gain of 4 dB.
45 MHz band-pass filter and amplifier
The 45 MHz IF signal is filtered through a 15 kHz-wide BPF Z101 and then amplified
by V109. It is filtered again by Z102. This removes the unwanted signals produced by
the first mixer.
Drawing 04-03369, or
Drawing 04-03542
Drawing 04-03378 (sheet 1)
NOTE If the PCB issue status is -06 or earlier, see drawing 04-03378 (sheet 1).
Drawing 04-03378 (sheet 1)
NOTE If the PCB issue status is -06 or earlier, see drawing 04-03378 (sheet 1).
Drawing 04-03378 (sheet 1)
NOTE If the PCB issue status is -06 or earlier, see drawing 04-03378 (sheet 1).
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