User Manual

Table Of Contents
DE
DANIELS
ELECTRONICS
UT-4R400 UHF Project 25
Digital
Transmitter
Instruction
Manual
4-1
4 Repeater
System
Configuration
4.1 Interim Repeater
The MT-4 series Project 25
Interim
Digital
Receivers
will
typically
be used in a low current
repeater
configuration
with MT-4 series Project 25
Interim
Digital
Transmitters. In its
Interim
mode of operation, the
receiver
can
demodulate
both FM analog and Project 25
digital
signals to
baseband audio. This audio can be passed to the Transmitter, where it can be
remodulated
as
either
a FM analog or Project 25
digital
signal. The voice signal will be
repeated
in
either
mode,
but other Project 25
digital
information
such as Network Addressing Code, Talk Group ID, and
low speed data will be lost. The
simplest
way of
setting
up a
repeater
system is to
connect
the
receiver
to the tra
nsmitter
through a Radio
Interconnect
Cable plugged into the CNTL BUS
connectors on the front panels of each radio module. This
cable
routes
received
audio and the
ANALOG_COR*
and
DIGITAL_COR*
signals to the transmitter, which is able to key in
either
Analog
or Project 25
Digital
mode.
Most users will
normally
want to have the
digital
repeater
set up to
re-transmit
an
incoming
signal
in the same mode as it is
received
(i.e.
normally, you would want a
received
analog signal to be
repeated
as analog and a
received
digital
signal to be
repeated
as digital). In the
interim
digital
repeater, this is
accomplished
in two steps.
1) The
receiver
determines
whether an
incoming
signal is analog or
digital
and asserts
either
the
ANALOG_COR*
or
DIGITAL_COR*
signal line to the transmitter.
2) When the
transmitter
senses an
ANALOG_COR*,
it keys up using one of the 16 channels
from Bank A, and when it senses a
DIGITAL_COR*,
it keys up using one of the 16
channels from Bank B.
The
transmitter
has two banks of 16
channel
s each,
called
Banks A and B. In the
interim
transmitter, it is suggested that Bank A is used for analog channels and Bank B is used for
digital
channels. This makes it easy to set up a
repeater
which
re-transmits
signals in the same mode in
which they were received. It is possible to program any
channel
in
either
bank to
either
analog or
digital
mode should this be required for
special
applications. The
transmitter
has two LEDs
labeled
A and D,
indicating
that the
transmitter
is keyed in
either
analog or
digital
mode. In the
interim
transmitter, these LEDs
actually indicate
that the
transmitter
is keyed in Bank A or B. Thus, if
Bank A channels are used for
digital
channels, the
Analog
LED
will
light
when the
transmitter
is
keyed on a Bank A channel, even though the
modulation
is digital. This problem will be
corrected
in the firmware upgrade to fully
compliant
Project 25 operation.
When
setting
up the
repeater
you would
typically
program the
transmitter’s
Bank A channels with
analog settings. Then you would program the corresponding channels in Bank B with the same
frequencies
but set them up for
digital
mode. The RSS makes this easier through the "Paste
Special
to Bank A and Paste
Special
to Bank B" menu
items
which allow copying of the frequency,
channel
name, and
timeout
value from all the channels in one bank to the corresponding channels
in the other bank.
It is
important
to note that the
receiver
and
transmitter
have no
connection
between them apart from
the audio and analog and
digital
COR* signals. This can lead to confusion since the
transmitter
doesn’t get any
information
from the
receiver
about which frequency or
channel
number to key up
on. The
transmitter
channel
is
determined
by the state of the CSEL0-3
channel
select
lines, and the
receiver
can only
tell
it to key on bank A (analog) or bank B (digital).