Specifications

13
Figure 3.2. Data signal flow diagram
Ext. Mod. signal flow in Transmitter
Level
Detector
Analog S/W
MC14053B
Data BPF
Sub-Audio LPF
MF6
Z1
Z
Y1
Y
Adj. Level
MCU
Check Audio In
Tone En
Audio In
Mod Out
Sub-Audio
Encoder
Y0
Z0
X1
X
X0
High : Audio In
Low : No Audio
Data Enable
Data In
Analog S/W
MC14053B
Sub-Audio LPF
MF6
Z1
Z
Y1
Y
MCU
Y0
Z0
X1
X
X0
Pre-Selector
RF Board
Sub-Audio LPF
4th Order
AF
IF IC
TA31136FN
RSSI
Comparator
MF6
Tone Detector
RSSI
Audio Out
Busy
Ext. Mod. signal flow in Receiver
BPF
30Hz ~
5KHz
Figure 3.3. External modulated signal flow diagram
b. FFSK & GMSK
Maxon provides two optional modem boards, ACC-513, GMSK and ACC-514, FFSK for
SD-160 to improve the efficiency for data transmission and offer maximum flexibility for
user application. Selection of the required modulation option is made installing wanted
modem to radio and programming several modem parameters through PC-programmer,
ACC-916. Modem board provides the facility to connect a computerized controller via an
RS-232 level serial data interface (i.e. Communication port COM1, COM2, etc. for PCs) to
its Slave MCU. Received data from controller(DTE) will then drive the FFSK or GMSK
modulator and allow transmission of serial data. It also provides FFSK or GMSK
demodulator for the reception of FFSK or GMSK modulated data signals. These are
converted to RS-232 level serial data stream for supply to a computerized controller.
In application of Sub-audio squelch, it can’t apply to GMSK modulated signal because of
their frequency confliction. But, FFSK modulated signal can be mixed with sub-audio
because it consists of two different continuous tones which frequency spectra are on the
audio frequency region.
Brief block signal flow diagrams for each optional modem board are the following (See
Figure 2.4. and Figure 2.5.).