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AWA RT-85 The
AWA RT-85 is a robust mobile VHF/UHF FM transceiver originally
designed for commercial and public service applications in
Australia. Manufactured
by Hitachi Denshi Ltd. for AWA, the RT-85 gained popularity among
amateur radio enthusiasts due to its durability and adaptability for
modifications.
Below
are the detailed technical specifications and features for the AWA
RT-85
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General
Specification
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Details
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Radio
Type
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Commercial-grade
FM transceiver (mobile/base use)
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Frequency
Coverage
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Original:
~440–480 MHz (VHF band)
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Other
models: 70–85 MHz and 136–174 MHz
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Modulation
Type
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FM
(narrowband and wideband, depending on configuration)
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Channel
Capacity
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60
channels (EPROM-programmed)
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Channel
Spacing
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Typically
12.5 kHz or 25 kHz
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Operating
Voltage
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13.8
VDC nominal (negative ground)
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Current
Consumption
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TX:
~7–9 A at 25 W
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RX:
~0.5 A (standby)
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RF
Output Power
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10–25
Watts nominal (model dependent)
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Antenna
Connector
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BNC
(50 ohms)
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Dimensions
(Main Unit)
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~250
mm (W) × 200 mm (D) × 60 mm (H)
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Weight
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Approx.
3.5 – 4.0 kg
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Cooling
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Passive
(heavy-duty aluminum heatsink), no fan
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Case
Construction
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Heavy-duty
die-cast metal chassis
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Transmitter
Specification
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Details
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Output
Power
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10–25
Watts nominal (model dependent)
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Modulation
Type
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Frequency
Modulation (FM)
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Modulation
Deviation
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±5
kHz (wideband typical), adjustable in software
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Spurious
Emissions
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>60
dB below carrier (typical for commercial compliance)
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Microphone
Input
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Front-panel
8-pin mic connector
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PTT
Control
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Hand
mic or remote keying via control head
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Duty
Cycle
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100%
at rated power with proper ventilation
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Reciever
Specification
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Details
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Receiver
Type
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Double
conversion superheterodyne
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IF
Frequencies
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1st
IF: 21.4 MHz
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2nd
IF: 455 kHz
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Sensitivity
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≤0.3
µV for 12 dB SINAD (typical)
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Selectivity
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~12–15
kHz @ –6 dB
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~25–30
kHz @ –60 dB (FM filter)
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Audio
Output
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≥2.5
W into 8 ohms (internal speaker or ext. jack)
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Squelch
Sensitivity
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Adjustable
via front panel and internally
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Mute
Control
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Carrier
or tone-based (programmable)
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Modifications
and Amateur Use
The
RT-85 has been widely modified for amateur radio use, particularly
for the 6-meter (50–54 MHz) band. Modifications
often involve:
However,
users have reported issues such as image rejection problems due to
the receiver's 21.4 MHz intermediate frequency (IF) and high-side
injection, leading to potential interference from strong broadcast
signals.
Variants
and Internal Architecture
The
RT-85 series includes several variants, notably the RT-85A, which
differ mainly in their microprocessor and EPROM configurations:
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Original
RT-85:
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RT-85A
Variant 1:
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RT-85A
Variant 2:
These
architectural differences affect the radio's programmability and
compatibility with modification software.
Programming
and Configuration
Programming
the RT-85 involves editing the EPROM contents to set frequencies and
operational parameters. Key
considerations include:
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EPROM
Types:
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Programming
Tools: Specialized
EPROM programmers compatible with the specific EPROM type are
required.
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Configuration
Data: Includes
settings such as maximum channel number, transmit timeout
values, and display options.
Detailed
configuration notes and EPROM data formats are available in
technical resources provided by amateur radio communities.
Resources
For
more in-depth information, consider consulting the following
resources:
TOP
OF PAGE
Page initiated 30 June
2025
Page
last revised 04 July, 2025
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