Kenwood TM-281A 144MHz FM Transceiver User Manual

Introduction

This manual provides essential instructions for the safe and efficient operation of your Kenwood TM-281A 144MHz FM Transceiver. Please read this manual thoroughly before using the transceiver to ensure proper setup and functionality. Retain this manual for future reference.

Safety Information

• Antenna Safety: Do not operate the transceiver without a properly connected antenna. Avoid touching the antenna during transmission.
• Power Supply: Use only the specified power supply voltage (DC 13.8V ±15%). Ensure correct polarity when connecting the power cable.
• Heat Dissipation: Ensure adequate ventilation around the transceiver, especially during high-power operation, to prevent overheating.
• Mobile Operation: When operating in a vehicle, ensure the transceiver is securely mounted and does not obstruct airbags or driver visibility.
• Water Resistance: The TM-281A is water-resistant, but it is not waterproof. Avoid submerging the unit or exposing it to heavy rain for extended periods.

Package Contents

Figure 1: Kenwood TM-281A Transceiver and included accessories. This image displays the main transceiver unit, a hand microphone, a mounting bracket, a DC power cable with an inline fuse, the instruction manual, and various small hardware components for installation.

Verify that all items listed below are included in your package:

• Kenwood TM-281A 144MHz FM Transceiver Unit
• Hand Microphone with DTMF Keypad
• Mobile Mounting Bracket
• DC Power Cable with Fuse Holder
• Hardware Pack (screws, washers, nuts)
• Instruction Manual

Setup

1. Mounting the Transceiver

Select a secure location in your vehicle or at your base station that allows for good ventilation and easy access to controls. Use the provided mobile mounting bracket and hardware to firmly attach the transceiver. Ensure the mounting location does not interfere with vehicle safety features or operation.

2. Power Connection

1. Connect the red lead of the DC power cable to the positive (+) terminal of your 13.8V DC power source.
2. Connect the black lead to the negative (-) terminal.
3. Ensure the inline fuse is correctly installed. For high-power operation (65W), a direct connection to the vehicle battery or a robust power supply is recommended.
4. Plug the power connector into the rear of the transceiver.

3. Antenna Connection

Connect a 144MHz VHF antenna (not supplied) to the antenna connector on the rear of the transceiver. Use a high-quality coaxial cable with appropriate connectors. Ensure the antenna is properly tuned for the 144MHz band to prevent damage to the transceiver.

4. Microphone Connection

Plug the hand microphone connector into the microphone jack on the front panel of the transceiver. Ensure it clicks securely into place.

Operating Instructions

1. Power On/Off and Volume

• Power On: Press the POWER button. The LCD will illuminate.
• Power Off: Press and hold the POWER button until the display turns off.
• Volume Adjustment: Rotate the VOL knob clockwise to increase volume, counter-clockwise to decrease.

2. Squelch Adjustment

The squelch circuit mutes receiver noise when no signal is present. Rotate the SQL knob clockwise to increase the squelch level (mutes weaker signals), and counter-clockwise to decrease it (allows weaker signals). Adjust until background noise is just muted.

3. Frequency Selection (VFO Mode)

1. Press the VFO button to enter VFO (Variable Frequency Oscillator) mode.
2. Rotate the MAIN DIAL to change the operating frequency.
3. Use the microphone's keypad to directly enter frequencies.

4. Memory Channel Programming

The TM-281A features 200 memory channels. Each channel can store frequency, offset, tone settings, and an alphanumeric name.

1. Select the desired frequency and settings (offset, CTCSS/DCS) in VFO mode.
2. Press and hold the M button until “CH STORE” appears on the display.
3. Rotate the MAIN DIAL to select the desired memory channel number (e.g., C001).
4. Press the M button again to save the settings to the selected channel.
5. To assign an alphanumeric name (up to 6 characters):
   • Press and hold FUNC to enter the Function Menu.
   • Navigate to “CHAN MENU” and then “NAME SET”.
   • Use the MAIN DIAL to select characters and the FUNC button to move to the next character position.
   • Press M to save the name.

5. CTCSS/DCS Operation

CTCSS (Continuous Tone-Coded Squelch System) and DCS (Digital Code Squelch) are used to filter out unwanted signals. Your transceiver supports both encoding and decoding.

1. In VFO mode, press FUNC, then navigate to the “CDT” (CTCSS/DCS Tone) setting.
2. Rotate the MAIN DIAL to select the desired tone mode (e.g., CTCSS, DCS, or OFF).
3. Press the MAIN DIAL to confirm.
4. Rotate the MAIN DIAL again to select the specific tone frequency or DCS code.
5. Press FUNC to exit the menu.

6. Weather Alert/RX

The TM-281A includes a Weather Alert/RX feature to receive NOAA weather broadcasts and alerts. Refer to the full instruction manual for detailed activation and usage of this feature.

7. Key Lock Function

To prevent accidental operation, the transceiver features a key lock function. Press and hold the H/L LOCK button to activate or deactivate the key lock. When active, most buttons and knobs will be disabled.

Specifications

Maintenance

• Cleaning: Use a soft, dry cloth to clean the transceiver. For stubborn dirt, slightly dampen the cloth with water. Avoid using harsh chemicals or abrasive cleaners.
• Connections: Periodically check all cable connections (power, antenna, microphone) to ensure they are secure and free from corrosion.
• Ventilation: Ensure the cooling fins on the rear of the transceiver are free from dust and obstructions to maintain proper heat dissipation.

Troubleshooting

Warranty and Support

For warranty information and technical support, please refer to the official Kenwood website or contact your authorized Kenwood dealer. Keep your purchase receipt as proof of purchase for warranty claims.