Modifying the Kenwood TKM-707 —a dedicated HF marine SSB radiotelephone—is primarily done to enable operation on amateur radio (Ham) bands or to expand its transmit range beyond the standard marine frequencies. ⚠️ Important Caution
Before attempting any internal modifications, ensure the unit is powered off and disconnected from its DC source. Modifications to marine equipment may void regulatory certifications (like FCC or USCG compliance) and are generally intended for use by licensed amateur radio operators. Common Modifications
Detailed step-by-step guides for these modifications are typically hosted on specialized community sites:
Expanded Transmit/VFO Mods: These allow the radio to transmit outside of the pre-programmed marine ITU channels, often covering the full 500 kHz to 30 MHz range that the receiver already supports.
MARS/CAP Expansion: Similar to other Kenwood models, this often involves removing specific diodes or resistors on the control board to unlock frequencies required for Military Auxiliary Radio System (MARS) use.
LSB (Lower Sideband) Support: By default, marine SSB typically uses USB (Upper Sideband). Modifications are sought by Ham operators to enable LSB, which is the standard for amateur bands below 10 MHz. Where to Find Schematics and Guides
Because these modifications require precise soldering on specific PCBs (such as the digital or TX-RX units), you should refer to dedicated technical repositories:
Mods.dk - Kenwood TKM-707: This is the primary community resource for this model. It contains user-submitted articles regarding VFO modifications and frequency expansions.
Repeater Builder: Excellent for sourcing the official Service Manual, which provides the circuit diagrams and component locations (like the PLL and control boards) necessary for identifying modification points. Essential Service Notes
Cold Solder Joints: A frequent "mod" or repair for this era of Kenwood digital PCBs (like the DG-1) is resoldering connections to fix frequency stability or display issues.
Internal Adjustments: Beep tone levels (VR7) and alarm tone levels (VR6) can be adjusted internally after removing the top cover. ssb radiotelephone - tkm-707 - Manuals (Repeater Builder)
Kenwood TKM-707 is a marine SSB radiotelephone, often confused with the amateur TM-G707 FM dual-bander. While "mods" for the marine version are less common than for its amateur cousins, they typically focus on frequency expansion or performance optimization. Common Modifications & Adjustments Frequency Expansion:
Like many Kenwood rigs of its era, frequency expansion can sometimes be achieved by modifying specific internal components. While specific diode/resistor locations for the are less documented than for the , community resources like
often host user-submitted guides for these specific marine models. Tone Level Adjustments:
The internal chassis contains several variable resistors (VR) for fine-tuning audible alerts: Beep Tone: to adjust the volume of the keypress beeps. Alarm Tone: Switch to Alarm Test mode and use to set the desired level for the 2182 kHz alarm tone. Antenna System Tuning:
Optimal performance depends heavily on the antenna setup. A common "mod" to improve poor reception involves ensuring the 17 ft whip antenna has a solid connection to a copper ground plane strip, often connected through hull fittings to the engine block to minimize RF interference. Key Technical Specifications kenwood tkm707 mods
For context when performing modifications, keep these core specs in mind from the TKM-707 User Manual Specification Power Output 150 Watts PEP (High Power) Frequency Range (RX) 500 kHz to 29.9999 MHz Operating Voltage (Do not use 24V) J3E (SSB), H3E (AM), CW Memory Capacity 198 channels (136 preprogrammed ITU + 62 user-defined) Important Precautions
The unit can get very warm during long transmissions or extended "HI" power operation. Ensure at least 15 cm (6 inches) of clearance behind the unit for ventilation. SWR Protection:
The radio includes a protection circuit that activates if the SWR is greater than 3. For best performance, aim for an SWR below 1.5. hammadeparts.jivetones.com or specific component values for the PLL circuit? Articles for Kenwood 'TKM-707' - mods.dk
The Story Begins
John, a seasoned ham operator, had been using his Kenwood TK-M707 as his primary transceiver for years. He loved its reliability, ease of use, and great performance on both HF and 6 meters. However, as he delved deeper into the world of digital modes and satellite communications, he realized that his trusty TK-M707 needed some upgrades to keep up with his evolving interests.
The Modification Goals
John identified several areas where he'd like to see improvements:
The Modification Journey
John spent hours researching and gathering information on various mods for the TK-M707. He scoured the internet, talked to fellow hams, and studied the radio's schematics to understand the necessary changes.
Digital Mode Support
To enable easy digital mode operation, John decided to install a USB interface kit specifically designed for the TK-M707. This kit included a cable that connected to the radio's ACC jack and a USB plug that went to his computer. He followed the kit's instructions and installed the necessary drivers on his PC. With this mod complete, John could now use his TK-M707 with popular digital mode software like WSJT-X and fldigi.
Improved TX IMD
John discovered that a common mod to reduce TX IMD on the TK-M707 involved adjusting the bias of the final amplifier transistors. He obtained the required documentation and tools, then carefully made the necessary adjustments. After testing, he was pleased to see a noticeable reduction in IMD on his transmitted signals.
Enhanced RX Sensitivity
To improve the receiver sensitivity, John decided to replace the TK-M707's original roofing filters with high-performance, narrow-band filters. These filters would help reduce the noise floor and improve selectivity. He sourced the filters from a reputable ham radio supplier and followed a detailed guide to replace the original filters. Modifying the Kenwood TKM-707 —a dedicated HF marine
AUX Port Modification
For the AUX port mod, John wanted to use it to control an external device, a satellite receiver. He studied the AUX port pinout and discovered that with a simple modification, he could repurpose one of the port's pins to provide a PTT (Push-To-Talk) output. This allowed him to control the satellite receiver's PTT function directly from the TK-M707.
The Results
After completing all the mods, John was thrilled with the results:
The Satisfaction
John was proud of himself for successfully completing these mods. He enjoyed the process of learning about his radio, understanding its inner workings, and making targeted improvements. His TK-M707, once a great radio, had now become an exceptional one, capable of handling a wide range of ham radio activities.
The mods not only breathed new life into his radio but also reignited John's passion for ham radio experimentation and exploration. He looked forward to making more contacts, trying new digital modes, and pushing the limits of his modified TK-M707.
I hope you enjoyed this story! Have you modified your Kenwood TK-M707 or have any questions about ham radio mods in general?
The Kenwood TKM707 is a legendary piece of 1990s audio engineering. While originally designed as a high-end marine VHF transceiver, its robust build quality and excellent receiver performance have made it a favorite for radio hobbyists looking to push the hardware beyond its factory limits.
If you’ve picked one up on the second-hand market, you’re likely looking for ways to modernize it or unlock its full potential. Here is a comprehensive guide to the most popular Kenwood TKM707 mods. 1. LED Backlight Conversion
The original TKM707 used small incandescent "grain of wheat" bulbs for the display and button backlighting. After decades of use, these bulbs often burn out or run excessively hot, which can eventually damage the plastic faceplate or LCD.
The Mod: Replacing these old bulbs with high-efficiency LEDs is a practical "quality of life" upgrade.
Implementation: Using diffused amber or warm white LEDs helps maintain the classic vintage look while significantly reducing the heat signature and power draw of the faceplate. This prevents the "baking" of the display components over time. 2. External Audio and Speaker Upgrades
While the TKM707 has a rugged internal speaker, it is optimized for high-volume marine environments rather than high-fidelity audio.
The Mod: Many users connect a high-quality external communications speaker to the rear jack for better clarity. Digital Mode Support : He wanted to use
Internal Filtering: Some hobbyists replace the internal electrolytic capacitors in the audio power amplifier circuit. Using modern, high-quality capacitors can sharpen the audio output and reduce background hiss that may have developed as the original components aged. 3. Improving Cooling for High-Duty Cycles
The TKM707 is built to be rugged, but continuous use can generate significant heat within the chassis.
The Mod: Adding a small, silent DC cooling fan to the rear heat sink is a common modification to ensure longevity.
Implementation: A fan can be mounted to the external heat sink and powered by the 13.8V rail. Utilizing a thermal switch allows the fan to activate only when the heat sink reaches a specific temperature, ensuring the final power transistors remain within safe operating limits during extended use. 4. Memory Battery Replacement and Maintenance
If the TKM707 fails to retain programmed channels after power-down, the CMOS backup battery has likely reached the end of its lifespan.
The Mod: Instead of soldering a new coin cell directly to the board, it is recommended to install a button cell battery holder.
The Benefit: This modification simplifies future maintenance, allowing for quick battery swaps without the need for additional soldering or extensive disassembly. Important Maintenance and Legal Note
Before performing any hardware modifications, it is important to remember that the TKM707 is a precision-tuned device. Improper handling can cause the radio to drift out of alignment. Always ensure that the device is operated within the legal parameters of its design and that all transmissions comply with local maritime and telecommunications regulations.
Is the goal for the TKM707 to maintain its original marine functionality, or is it being restored for stationary monitoring in a radio shack?
You're looking for modifications (mods) for the Kenwood TK-M707, a popular amateur radio transceiver. Here are some in-depth details on various mods that enthusiasts and users have explored:
By default, the TKM-707 is restricted to the standard 2-meter amateur band (144–148 MHz). However, many operators wish to transmit on MARS (Military Auxiliary Radio System) or CAP (Civil Air Patrol) frequencies, which lie just outside the ham bands.
The Procedure: Unlike modern software-defined radios, the TKM-707 often requires a hardware modification to unlock extended transmit capabilities. This usually involves locating a specific diode or jumper on the control board.
Note: While this opens the hardware capability, you must legally possess a license to transmit on these out-of-band frequencies.
The Kenwood TKM-707 is a legendary transceiver in the amateur radio community. Known affectionately as the "Commercial Grade" mobile rig, this 2-meter radio has developed a cult following due to its robust receiver front end, simple interface, and rock-solid transmit audio. Originally designed for the commercial land mobile market, many of these radios have found their way into the hands of amateur radio operators.
However, because the TKM-707 was built for specific commercial bands, "out of the box" performance for the average ham can be limited. Whether you are looking to expand the frequency range, improve the audio quality, or simply modernize the internals, modifying the TKM-707 is a rite of passage for owners.
Here is a comprehensive guide to the most popular and effective modifications for the Kenwood TKM-707.
The TKM-707 is robust, but age reveals weaknesses. These are worth addressing before they fail.
