Motorola V186 - Cell Phone - GSM System Planner Manual page 126

Conventional and Analog Trunked Radio Modulation Types
The physical interface to the conventional or analog trunked radio is through a plug-in
radio modem board on the CPU module; the characteristics programmed into the plug-in
modem determine the emission characteristics of the radio. The data may directly
modulate the FM transceiver's oscillator to most effectively use the radio bandwidth.
Motorola refers to this modulation technique as DFM; in the U.S. this is also described
by the FCC as an F1 emission. The figure below shows the modulation sideband created
by DFM. FCC licenses specifically state when F1 emission may be used and only radios
having an F1 emission designator may be used in those licensed systems. No F1 emission
is suitable when intermediate amplifiers (voice/RT repeaters) are present and should not
be used with PL/DPL, but F1 emissions are fully compatible with the ACE3600 store-&-
forward operation.
The data may instead modulate a tone oscillator to produce a variable tone or variable
phase output; this signal output then modulates the FM transceiver's oscillator. Motorola
refers to this modulation technique as FSK (variable tone) or DPSK (variable phase). The
figures below show the modulation sidebands created by FSK and DPSK. The FCC has
revised the rules governing the use of these emissions, so please read carefully the
Refarming section below. FSK or DPSK must be used whenever any intermediate
amplifier (voice/RT repeater: conventional or trunked) is present; DPSK must be used
when any degraded bandwidth condition (notch filters, etc.) exists, and DPSK is the only
emission allowable in the U.S. VHF splinter channels. FSK and DPSK are also fully
compatible with store-&-forward operation.
Note: Intrac modulation is not supported in ACE3600.
PL & DPL
Private Line (PL) and Digital Private Line (DPL), also known as Continuous Tone-Coded
Squelch System (CTCSS), was created for voice users of two-way radio to suppress
activity from other co-channel users from being heard; it offered the illusion of a private
channel. PL/DPL adds a decoder to the receiver that keeps the receiver muted until a
signal having a specific low-frequency tone (PL) or slow data code (DPL) is received. All
transmitters must encode the proper tone/code to open the protected receiver. Some
repeaters, notably those in the UHF band, use PL or DPL to prevent unwanted access to
the repeater system by co-channel users.
Modulation Data Speeds in bps
(* = recommended)
Technique
COS 9600
DFM 4800(*), 3600, 2400
FSK 2400(*), 1800
DPSK 1200
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Communications