Kenwood FM-1

The Kenwood FM-1 is an AM/FM terminal unit for amateur radio RTTY work. It was meant to pair with the TS-520 and TS-820 transceivers, and it sold new for $190. Little else is formally documented about it. What record exists comes from owner reviews and forum discussion, and all of it is positive. Period audio publications covered Kenwood's expanding line of AM/FM equipment, which shows the company's growing presence in the market Audio (September 1962, p.81).

The FM-1 is fully solid state, built entirely from discrete components, and offers both AM and FM modes for RTTY. It was marketed as a replacement for the older tube-based TU units common in RTTY shacks of the era. Known specs are modest: 600 ohm input impedance, 2 W power output, and a frequency response of 250 to 5000 Hz. Tuning is done by crystal, with a trimmer for setting the exact frequency. An internal pot adjusts the percentage of modulation.

One owner review on eHam.net (September 27, 2009) rated the FM-1 5 out of 5. The reviewer said it "works as designed," is easy to work on, and has good, complete documentation. The same reviewer found it works well as a standalone RTTY unit. Forum feedback from qrz.com agrees. It describes the FM-1 as highly flexible and well-built, with good audio quality and solid RTTY performance alongside the TS-520. No negative criticism appears anywhere in the surviving record.

Several things are not documented: production years, dimensions, weight, rear-panel connections, filter or crystal options, and any distortion or sensitivity figures.

Type: AM/FM terminal unit for RTTY
Original price: $190
Input impedance: 600 ohm
Power output: 2 W
Frequency response: 250–5000 Hz
Circuitry: all discrete components, fully solid state
Designed for use with Kenwood TS-520 and TS-820