Specifications

11
Squelch Options
Compared to existing Maxon data radios, programmable sub-audio squelch system (CTCSS &
DCS) and two-tone squelch system are newly added. Each channel will have these squelch
option sets during dealer programming. More detail descriptions for all available squelch
systems of SD-160 are the following.
Sub-audio squelch system
The SD-160 can operate singly or with optional modem boards. Even if user wants to use sub-
audio SQ system, the radio will permit this SQ option according to some cases to avoid
confliction between sub-audio and data.
Contrary to general-purpose two-way radio, the input of the radio is data or audio. In case of
audio, its frequency spectra are limited to 300㎐ ∼ 3㎑ by internal BPF. So, the division of this
and sub-audio is possible on the frequency spectra because sub-audio has under 300㎐
frequency. But, Data has wide frequency spectra compared with audio. Normally, that has 30㎐
∼ 4.8㎑ frequency (except harmonic freq.) at 9600 baud rate. Accordingly, the conflict of sub-
audio and data are inevitable and so broken data or SQ error is unavoidable. To solve this
problem, the radios can use the FFSK modulation which converts data into two different
continuous audio tone according to their logic levels. Therefore, available cases of sub-audio
SQ system are Audio and FFSK signal. But, it’s not permitted to FSK(FM direct modulation of
data) and GMSK signal.
a.Single operation of SD-160
If the radio operates singly, only FM direct modulation/demodulation of audio and data are
available. In this case, audio and data are inputted and released through different DB
connector lines which pin 7, 9, 1 and 2 of DB-15 connector are used as audio input, audio
output, data input and data output, respectively. Normally, Sub-audio Squelch(SQ) System
can be applied to audio signal, but data doesn’t use it to avoid frequency confliction. So, if
user tries to transmit data in one channel which has sub-audio squelch option, radio will
flash green LED two times as warning and then transmit it without sub-audio.
Note : SD-160 provides the connection of external modems to receive and transmit
external modulated data which can be inputted and outputted through pin 1 and 2