Receive Path; Input Low-Pass Filters; Broadcast Filter And Rf Amplifier; First Mixer - Codan NGT 2010 RF Technical & Service Manual

NGT—Technical description (2011/2012)

Receive path

Input low-pass filters

Drawing 04-03369, or
Drawing
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

Drawing
NOTE
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

Drawing
NOTE
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

Drawing
NOTE
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.
116
04-03542
04-03378 (sheet 1)
If the PCB issue status is -06 or earlier, see drawing
04-03378 (sheet 1)
If the PCB issue status is -06 or earlier, see drawing
04-03378 (sheet 1)
If the PCB issue status is -06 or earlier, see drawing
04-03378 (sheet
04-03378 (sheet
04-03378 (sheet
NGT Transceiver System Technical Service Manual
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