FCC ID : AK8NTM30
Model : NTM-30
CIRCUIT DESCRIPTION of ICB-U655
ICB-U655 is a FRS(Family Radio Service) Tranceiver with 14 radio channels.
1ch 462.5625MHz 8ch 467.5625MHz
2ch 462.5875MHz 9ch 467.5875MHz
3ch 462.6125MHz 10ch 467.6125MHz
4ch 462.6375MHz 11ch 467.6375MHz
5ch 462.6625MHz 12ch 467.6625MHz
6ch 462.6875MHz 13ch 467.6875MHz
7ch 462.7125MHz 14ch 467.7125MHz
Part RX
Circuit system of ICB-U655(Part RX) is double conversion superheterodyne (lower
heterodyne). An incoming RF signal received through the Antenna goes through the
antenna switch (D1, D2, and D3) and is amplified at the RF Amplifier (Q1). The signal
is converted to a first Intermediate Frequency (IF:21.7MHz) at a first mixer (IC1). The
first Local Oscillator is a Phase Locked Loop (PLL) synthesized oscillator being varactor
tuned, which is variable between 440.8625MHz to 446.0125MHz in RX mode. The first
mixer is a Double Balanced Mixer (DBM). The first IF signal is amplified at a IF
amplifier (Q2) and is converted to the second IF of 450kHz at a second Mixer in the IF
IC (IC2). The second IF signal is demodulated at a FM demodulator in the IF IC (IC2).
The demodulated signal input to the Tone generator/detector IC (IC109) by which the
tone squelch circuit, de-emphasis, and HPF combine, and the tone squelch signal and
AF (Audio Frequency) signal are separated in IC109. The AF signal is amplified at an
AF Amplifier (IC102) and a Speaker connected to the AF Amplifier. Finally, the audible
signal is heard through a internal speaker.
