This is less of a hardware mod and more of a programming exploit using the front panel.

Steps to enable "Screwdriver" VFO mode:

Result: The tuning dial now behaves like a true VFO. You can tune from 1.600.00 to 29.999.99 MHz in continuous 10 Hz steps. This is essential for chasing SSB nets or tuning in digital modes like FT8.

The TKM-707 is a marine radio. Marine HF uses Upper Sideband exclusively (except for some inter-ship on 2 MHz, which sometimes uses J3E - similar). Amateur radio uses LSB on 160, 80, and 40 meters. Without LSB, you can only listen to half the conversations.

The radio has a sharp Collins mechanical filter (often 2.4 kHz for SSB). For AM broadcast listening or DRM, this is too narrow.

The radio generates its carrier frequency based on a 9 MHz IF (Intermediate Frequency). To switch from USB (+1.5 kHz offset) to LSB (-1.5 kHz offset), you need to alter the BFO (Beat Frequency Oscillator) injection.

Hardware Method (Adding a switch):

Software/Service Menu Method (Some firmware versions):

Result: A flip of a switch gives you full LSB capability on 75m and 40m rag-chews.

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.

Modifications and Performance Evaluation of the Kenwood TKM-707 Handheld Transceiver