The Kenwood TKM-707 is a high-performance SSB Marine Radiotelephone known for its rugged 150-watt output and expansive memory capabilities. While primarily designed for the marine market, its reliability has made it a popular candidate for various technical adjustments and modifications to suit amateur radio or specialized communication needs. Technical Profile & Core Features
Before diving into modifications, it is essential to understand the platform's robust baseline:
Power Output: Delivers a full 150 watts PEP for long-distance marine and HF communication.
Frequency Range: Covers marine bands from 2 MHz to 27.8 MHz with a general coverage receiver spanning 500 kHz to 300 MHz.
Memory: 198 total channels, including 150 preprogrammed ITU channels and 62 user-programmable spots.
Chassis: Utilizes a heavy-duty, rustproof aluminum chassis with a massive cooling system for continuous transmission. Common Maintenance & Performance "Mods"
Most documented "modifications" for the TKM-707 focus on performance optimization and internal levels rather than extensive hardware overhauls. These are often found in the TKM-707 Service Manual . Internal Level Adjustments:
Beep Tone Level: VR7 can be adjusted to change the volume of the internal confirmation beeps.
Alarm Tone Level: VR6 controls the level of the 2182 kHz alarm tone used in emergency tests. Kenwood Tkm-707 Mods
Signal Reliability Mods: Intermittent reception issues are frequently tied to grounding rather than internal circuit failure. Users often "modify" their installation by securing the 17 ft whip antenna to a dedicated copper ground plane strip and ensuring solid connections to thru-hull fittings to minimize RF interference. Advanced & Community Modifications
For those looking to push the device beyond factory specs, enthusiasts often look toward the Mods.dk archive for specialized community-submitted guides.
Expanded Coverage: While the TKM-707 is already broad, some regional versions have restrictions that can be bypassed via specific diode or resistor removals on the control board, similar to the logic used for the TM-G707 amateur model (though the specific component numbers differ).
Digital Mode Integration: Connecting the TKM-707 to modern digital interfaces for modes like FT8 or Winlink often requires custom cabling for the 6-pin MIC connector or external tuner ports.
DG-1 Digital Display Fixes: Owners of older Kenwood HF units (sharing similar technology) often perform a "cold solder" mod. If the digital display becomes erratic, resoldering the 18 points on the digital PCB often restores full function. Important Precautions
Modifying marine equipment requires caution, as these devices are life-safety tools.
The Kenwood TKM-707 is a legendary marine HF/SSB transceiver often sought after by amateur radio enthusiasts for its rugged build and 150-watt output. Modifying this "boat anchor" to work on ham bands is a common "story" of transformation in the radio community. The Ham Radio Conversion Story
was originally factory-locked to marine frequencies (2 MHz to 30 MHz for RX, but restricted TX). Operators wanting to use it for amateur radio typically focus on several key modifications: The Kenwood TKM-707 is a high-performance SSB Marine
Extended Transmit (MARS/CAP): Standard units often will not transmit on amateur bands out of the box. While specific "diode-cutting" steps vary, the goal is to unlock the PLL (Phase Locked Loop) to allow the transmitter to follow the general coverage receiver across the 500 kHz to 30 MHz range.
VFO and Sideband Mods: Marine radios are often channelized or limited to Upper Sideband (USB) for distress frequencies like 2182 kHz. Modders look for ways to enable Lower Sideband (LSB) for the 40m and 80m ham bands and full VFO (Variable Frequency Oscillator) tuning.
Antenna Coupler Integration: Many users pair the 707 with the Kenwood MAT-100 or MAT-300 external automatic antenna tuners. Custom interface cables are often a "mini-mod" project to ensure the radio can trigger the tuner with a single button press. Known Technical Maintenance
Reliability often requires addressing classic aging issues found in Trio-Kenwood gear:
Cold Solder Joints: A frequent "mod" is actually a repair—resoldering the digital PCBs to fix intermittent display or logic issues, a problem noted in similar Kenwood service bulletins.
Audio Tweaks: Some users perform "low audio fixes" or mic gain adjustments to improve voice punch on SSB. Where to Find Specific Guides
Detailed schematics and step-by-step modification logs are archived on enthusiast sites: Mods.dk hosts a repository of specific articles, including VFO mods and transmit expansions.
Scribd provides the full service manual, which is essential for identifying the correct test points for alignment after any modification. Articles for Kenwood 'TKM-707' - mods.dk Find the microphone pre-amp IC (IC8
Disclaimer: Modifying this radio may violate terms of service for marine band use, void legal certification, and require an amateur radio license. Incorrect modifications can damage the final amplifier. Proceed at your own risk.
Out of the box, the TKM-707 is often locked to specific commercial frequencies. For the amateur radio operator, the most critical modification is opening up the transmit and receive range to cover the entire 2-meter band (144–148 MHz).
This is almost exclusively a software modification. Unlike older radios that required cutting traces or soldering diodes, the TKM-707 is programmed via a cable connected to a PC.
Modifications and Performance Evaluation of the Kenwood TKM-707 Handheld Transceiver
Absolutely. You can buy a used TKM-707 for $200–$300. After the frequency expansion mod, you have a 150W SSB radio with a receiver that rivals the Icom IC-7300 in terms of dynamic range (the TKM-707 uses a double-conversion superheterodyne with a RF MOSFET preamp).
Compared to modern Chinese 100W radios, the Kenwood is quieter, has no birdies, and produces a clean signal. The only missing features are a spectrum scope and built-in sound card.
To increase talk power (without overdriving):
The TKM-707 does not support Kenwood CI-V natively. Some operators have built an Arduino translator that reads BCD from the PLL and writes to an emulated CI-V bus – a complex mod requiring PLL injection point access.