The AF signal re-modulated in the IC201 goes through the de-emphasis circuit consisting
of R204 and C209 and will be amplified in the Q201. A 2-stage HPF consisting of Q202,
C210, R212, C220 and R211 is used to reject AF signal below 300Hz. The AF signal from
the HPF goes through variable resistor RV202 and is input to the speaker amplifier circuit
IC104 and amplified to the set output level.
6) Audio Muting Circuit
The Q105 to mute the audio is controlled by input of squelch’s BUSY signal and the mute
output of the CPU IC101.
7) WX Alert Detection
The tone selector IC105 detects the 1050Hz alert tone if it is contained in the re-modulated
AF and the WX alert tone will be output from the speaker.
4.4 SPECIFICATIONS
4.4.1 Transmitter
Channels All available US,INT, Canada VHF Marine band
Frequency Stability 10 PPM (0.001%) from -20
o
C to +50
o
C
Frequency Range 156.025 to 157.425 MHz
Channel Spacing 25 KHz increments
Power Output Switchable 5W, 3W, 1W into 50 Ohms at 6.0 VDC
Modulation Frequency. Modulated 16F3 (4.5 KHz at 1000Hz)
Modulation Audio Shall not vary1/3 dB from true 6 dB pre-emphasis
response from 300 to 2500 Hz, reference 1000 Hz.
Audio frequencies 3-20 KHz shall be attenuated
(at 1 KHz by 60 log f/3 dB. Above 20 KHz by 50
dB)
FM Hum & Noise Level greater than-40 dB below audio
Audio Distortion Less than 10% at 1 KHz for3 KHz deviation
Spurious & Harmonic Attenuated at least 4310 log Po (below rated
radiated carrier power) per FCC Rules Parts 2 &
80
Antenna Impedance 50 Ohms
Transmitter Protection Shall survive open or short circuit of antenna
system without damage (10 min. test)
4.4.2 Receiver
Channels All available US,INT, Canada VHF Marine band
Frequency Range 156.025 to 163.275 MHz in 25 KHz increments
Frequency Stability 10 PPM (0.001%) from -20
o
C to +50
o
C
