Kenwood Tkm707 Mods

On many TKM-707 units, you can’t type “14.250” directly. Instead, you must scroll. However, some firmware versions allow:

The Kenwood TKM-707 is a rugged, 150-watt PEP marine SSB transceiver, widely used on commercial and recreational vessels. Its popularity among amateur radio operators (hams) stems from its robust build, high output power, and relative affordability on the used market. However, the unit is factory-locked to marine frequencies (1.6–30 MHz, primarily in 2 kHz steps for ITU channels). This report details the most requested modifications to expand frequency coverage, improve performance, and adapt the unit for general coverage and amateur bands.

The TKM-707 is rated for 150W PEP. However, many units drift with age, and the final transistors (2SC2879) can be pushed further – but do so at your own risk. The most useful mod here is reducing power for digital modes and setting a stable 100W carrier. kenwood tkm707 mods

The S-meter on the TK-M707 can sometimes be less accurate. Calibration mods can improve the precision of signal strength readings.

If you operate mobile or in a high-RF noise environment, you can add a pre-amp bypass or tap the IF output to connect a Timewave DSP-599zx or similar. On many TKM-707 units, you can’t type “14

| Aspect | Stock TKM-707 | Modified Unit | |--------|---------------|----------------| | TX Frequency | Marine channels (2 kHz steps) | 1.6–30 MHz continuous (10 Hz steps) | | TX Power (PEP) | ~100W | Adjustable 20–150W | | Clarifier Range | ±10 Hz (RX only) | ±1.5 kHz (RX+TX) | | Legal Use | Marine (Part 80) | Requires amateur license (Part 97) |

Harmonic suppression: After expansion, ensure operation within amateur bands where the TKM-707’s low-pass filters are still effective (designed for marine bands). Spurious emissions may rise outside 4–26 MHz. Verdict: Stick to 120-150W PEP max

Some guides suggest cranking VR5 until you see 200W PEP. The 2SC2879 pair can theoretically handle this, but the TKM-707’s power supply and heat sink are not designed for sustained 200W. Doing so will lead to:

Verdict: Stick to 120-150W PEP max. Clean power is better than dirty watts.