Midland SD-225V2 User manual

User’s Guide
SD-225 Series
16 Channel UHF/VHF Data Radio
www.midlandradio.com

SD-225 User’s Guide
2©2006, Midland Radio Corporation
FCC RF EXPOSURE COMPLIANCE REQUIREMENTS FOR
OCCUPATIONAL USE ONLY
The Federal Communications Commission (FCC), within
its action in General Docket 93-62, November 7, 1997,
has adopted a safety standard for human exposure to
Radio Frequency (RF) electromagnetic energy emitted
by FCC regulated equipment. Midland Radio Corporation
subscribes to the same safety standard for the use of its
products. Proper operation of this radio will result in user
exposure far below the Occupational Safety and Health
Act (OSHA) and FCC limits.
This radio is NOT approved for use by the
general population in an uncontrolled
environment. This radio is restricted to
occupational use, work related operations only,
where the radio operator must have the
knowledge to control the user’s exposure
conditions for satisfying the higher exposure
limit allowed for occupational use.
DO NOT transmit for more than 50% of total use
time (50% duty cycle). Transmitting more than
50% of the time can cause FCC RF exposure
compliance requirements to be exceeded.
The antenna used with this radio should not have
gain of more than 6 dBi. Make sure no one is
closer than 20 inches to the antenna when
transmitting. The radio is transmitting when the
red LED on the cover of the radio is illuminated.
You can cause the radio to transmit by grounding
pin 3 on the radio connector.
!These are required operating conditions for
meeting FCC RF exposure compliance. Failure to
observe these restrictions means violation.

SD-225 User’s Guide
©2006, Midland Radio Corporation 3
Contents
Conventions and Symbols in this Book ................................... 4
Disclaimer ................................................................................ 4
Safety....................................................................................... 4
Introduction .............................................................................. 6
Radio Models ....................................................................... 6
Radio Features..................................................................... 6
Recommended Accessories and Options ............................ 7
Radio Connections................................................................... 8
Connection Overview ........................................................... 8
External Interface ............................................................... 10
DB9 Radio Interface Connector Details ............................. 10
Setup and Operation.............................................................. 12
Mounting............................................................................. 12
Channel Selection .............................................................. 12
Status LED ......................................................................... 13
Specifications......................................................................... 14
Warranty Statement ............................................................... 15

SD-225 User’s Guide
4©2006, Midland Radio Corporation
Conventions and Symbols in this Book
This symbol marks a “caution”. Cautions are special notices
which you should read and follow carefully to avoid possible
damage to your equipment and to avoid potential danger to
yourself or other people.
!This symbol marks an “important point”. Important points are
specific instructions which should be followed closely for proper
operation.
This symbol marks a “note”. Notes are hints or tips which offer
additional information to help you.
Disclaimer
Midland Radio Corporation is committed to continuous quality
improvements, for this reason specifications may change without
prior notice.
Every effort has been made to ensure that the information in this
document is complete, accurate, and up-to-date. Midland
assumes no responsibility for the results of errors beyond its
control. The manufacturer of this equipment also cannot
guarantee that changes in the equipment made by unauthorized
people will not affect the transceiver’s performance or functions.
Safety
Your SD-225 data radio has been carefully designed to give you
years of safe, reliable performance. As with all electrical
equipment, however, there are a few basic precautions you
should take to avoid injury to yourself or damage to the radio:
Read the instructions in this book carefully. Be sure to save it for
future reference.
Read and follow all warning and instruction labels on the radio
itself.
Do not operate the radio near unshielded electrical blasting caps
or in an explosive atmosphere.

SD-225 User’s Guide
©2006, Midland Radio Corporation 5
Do not operate the transmitter of any radio unless all RF
connectors are secure.
All equipment must be properly grounded for safe operation.
Do not allow children to operate or play with or near the radio
equipment.
Never attempt to service the radio yourself. All equipment should be
serviced by a qualified technician. Contact you local dealer or
communications coordinator for assistance.
Do not allow the antenna to touch or come in very close proximity
with the eyes, face, or any exposed body parts while the radio is
transmitting.
The above warning list is not intended to include all hazards that may
be encountered when using this radio.

SD-225 User’s Guide
6©2006, Midland Radio Corporation
Introduction
Congratulations! By choosing the Midland SD-225 data radio,
you have selected a flexible, easily configured communication
device. Its rugged design will provide years of reliable service
and exceptional performance.
Radio Models
The SD-225 data radio is available in three frequency ranges.
SD-225V2: 5 W, VHF high band, 148-174 MHz
SD-225U1: 5 W, UHF high band, 400-440 MHz
SD-225U2: 5 W, UHF high band, 440-480 MHz
Radio Features
The SD-225 series data radio is a programmable, synthesized
16 channel radio featuring:
5Compact, rugged die cast enclosure.
5Tri-color LED for operating, warning and programming status
indications.
59-18 Vdc supply voltage operating range.
55 Watts transmit power. A low power selection (1 Watt) may be chosen
if full power is not needed.
512.5 KHz and 25 KHz channel spacing, programmable per channel.
549 CTCSS tones / 104 DCS codes available, programmable per
channel.
5Software adjusted noise squelch level. The squelch opening and closing
levels may easily be set using the programming software and an RF
signal generator.
5External modem / direct FM modulation input.
5Bell 202 / V.23 internal 1200 baud modem option.
5Busy channel lockout feature may be programmed. An override function
for matched sub-audible is available to allow transmission during
repeater hangtime.

SD-225 User’s Guide
©2006, Midland Radio Corporation 7
5Transmit time-out timer may be programmed to limit continuous
transmission time.
5Transmit hang timer may be programmed to keep the transmitter active
for a short time after the PTT signal is removed..
5Basic radio controls (transmit mode, receive mode, channel change,
and modem test) are available via serial commands.
Recommended Accessories and Options
Software
ACC-917 PC programming and adjustment software
Cables
ACC-2025 USB PC programming cable
Options
ACC-512? Bell 202/V.23 internal 1200 baud modem

SD-225 User’s Guide
8©2006, Midland Radio Corporation
Radio Connections
Connection Overview
The SD-225 features two standard interfaces. The data interface
is used for connection to external modems and provides flat,
unfiltered input and output. The audio interface is used for voice
and some voiceband (300 – 3000 Hz) signaling applications.
If the internal modem option is installed, the data
interface may be configured for direct asynchronous
RS232 data input and output. PTT and Busy may also
be configured for RS232 levels. More information using
the internal modem is available in the modem manual.
Once the interface type is selected, the appropriate connections
may be chosen based on the information given below.
Power Connection
The SD-225 needs a stable 12V DC power source, capable of
supplying at least 2 amps of current. The power connections
should be made to DB9 pins 4 (-) and 5 (+).
The nominal input voltage for the SD-225 is 12 Vdc, but
it is capable of operating in a 9-18 Vdc range.
PTT Connection
A connection to the PTT input, DB9 pin 3, is required to put the
SD-225 into transmit mode. Switching the PTT input to 0V will
initiate transmit mode. With the internal modem option, the PTT
input may be changed to RS232 level.
Busy Connection
A connection may be made to the BUSY_DET output, DB9 pin 6,
which indicates the receive status of the SD-225. Pin 6 is
normally +5Vdc and switches to 0V when a signal exceeding the
programmed squelch threshold is received. If CTCSS/DCS is
programmed on the channel, the CTCSS/DCS must also be

SD-225 User’s Guide
©2006, Midland Radio Corporation 9
decoded, before pin 6 will switch low. With the internal modem
option, the BUSY output may be changed to RS232 level.
Modulation Input Connections
The two choices for modulation are DATA_IN, DB9 pin 1 or
MIC_IN, DB9 pin 7. When the SD-225 is used in low speed data
applications (with an external modem), the modem data to be
transmitted is usually connected to pin 1. The SD-225 connects
the pin 1 input to the transmitter by default.
For audio applications, the transmit audio is usually connected to
pin 7. The SD-225 must detect a load on pin 7, before it will
switch pin 7 into the transmit circuit. This load could be a
microphone element that is switched into the circuit by PTT.
Alternatively, a 10Kresistor may be connected from PTT (pin
3) to MIC_IN (pin 7). This will load pin 7 when transmitting.
Pin 7 has a second function in receive mode. If this pin is
switched low in receive mode the SD-225 will enter
monitor mode (open squelch). The MIC_IN load should
only be in the circuit during transmit mode. It may be
necessary to use an A/C coupling capacitor from the
external modulation source to prevent the SD-225 from
entering monitor mode.
Demodulated Output Connections
The demodulated output from the receiver is available on
DATA_OUT, DB9 pin 2 and SPK_OUT, DB9 pin 9. For low
speed data applications, the flat, discriminator output, pin 2, is
usually connected to the external modem. Pin 2 will provide 200-
300 mVrms into a 10Kload when receiving a 1 KHz audio
signal modulated at 60%.
For audio applications, the bandpass filtered (300 – 3000 Hz)
and de-emphasized audio available on pin 9 is typically used.
Pin 9 is adjusted for a nominal 1 Vrms into an 8load, when
receiving a 1 KHz audio signal modulated at 60%. RV403 may
be used to adjust the pin 9 output level.

SD-225 User’s Guide
10 ©2006, Midland Radio Corporation
External Interface
1. DB9 male: modulation input, demodulation output, control inputs and power
supply.
2. BNC female: antenna connection.
DB9 Radio Interface Connector Details
2.5 in
4.6 in
1.2 in