The Kenwood TKM-707 is a legend. Built like a tank for the marine market, it has found a second life in the shacks of amateur radio operators who crave a rugged, high-performance HF transceiver. Why? Because it shares DNA with the famous Kenwood TS-450, but you can often pick one up for a fraction of the price.
However, the TKM-707 came out of the box with maritime restrictions. To make it sing on the ham bands, you need to perform a few key modifications.
Disclaimer: These modifications are intended for licensed amateur radio operators only. Transmitting out of band is illegal and can result in hefty fines. Proceed at your own risk.
Here are the top three mods every TKM-707 owner should know about.
Goal: Enable transmit on amateur HF bands (e.g., 80m, 40m, 20m). Kenwood Tkm-707 Mods
Common method (board-level):
Result: TX from 1.6–30 MHz continuous (subject to hardware limits).
Risk: Spurs, harmonics, reduced output filtering.
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 Kenwood TKM-707 is a legend
The Kenwood TKM-707 is a 150W HF SSB transceiver (RX: 0.5–30 MHz, TX: 1.6–27.5 MHz marine bands). Despite its commercial focus, amateur operators have developed several modifications to expand frequency coverage, improve performance, or enable external control.
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.
The TKM-707’s clarifier is great for fine-tuning marine nets, but it lacks the range for SSB phone rag-chewing where operators might drift. Result: TX from 1
The Fix: Locate the trimmer capacitor (TC1) on the PLL board. By tweaking this or replacing a fixed resistor in the clarifier circuit (R158), you can expand the adjustment range from ±50Hz to ±200Hz.
Why you need it: This turns the clarifier from a "fine tune" into a proper "voice finder." No more asking the other station to re-tune their Drake.
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.