The TKM-707 ships with USB only. To get LSB for 40m/80m/160m:
Note: Some units need a 4.9152 MHz crystal swap for proper LSB filter alignment. Rare but possible.
The "proper story" behind the Kenwood TKM-707 modifications is a classic tale of 1990s radio engineering: a high-quality piece of consumer hardware that was secretly a professional-grade transmitter waiting to be unlocked. kenwood tkm707 mods
Here is the history, the technical reality, and the specific modifications for the Kenwood TKM-707.
| Modification | Purpose | User Type | |--------------|---------|------------| | MARS/CAP Mod | Expand TX frequency range (e.g., 1.6–30 MHz continuous) | Amateur radio, Military Affiliate Radio System (MARS) | | Clarifier Unlock | Allow fine tuning beyond ±10 Hz for USB/LSB | DX communications | | Power Adjustment | Reduce or increase RF output (e.g., 20–150W) | Digital modes, amplifier driving | | Display Lighting | Replace failing EL backlight with LED | General usability | | Audio Improvements | Modify receive audio filtering or add external speaker jack | Audio fidelity | The TKM-707 ships with USB only
If you own an older unit, you may notice the LCD display is dim or has "spiderweb" cracks in the black background. This is a common aging issue with LCDs from the 90s.
The LED Backlight Swap: The original design often used incandescent bulbs or early LED strips that have faded. Note: Some units need a 4
If you find a TKM-707 for under $300, do the MARS mod + power adjustment + backup battery. Skip the 200W temptation and the advanced IF tap unless you love tinkering. For under $400 total invested, you’ll have a rugged, high-power HF rig that will survive a lightning strike better than any modern SDR.
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.