Equipment / Base transceiver · Collins Radio
discontinued

Collins KWM-2/2A

$$$$·

80m – 10m
Bands
100 W
Output
1959
Introduced
FrequencyTX/RX: 80–10 m (amateur)
Bands80m, 40m, 20m, 15m, 10m
TX power100 W (175W PEP input SSB, 160W input CW. ~100W nominal output. Tube finals.)
ModesUSB, LSB, CW
Weight10.4 kg (22.9 lb) - ~10.4 kg (transceiver only, external PSU adds ~14.5 kg). Compact for tube era.
ConnectorSO-239
Year1959
Connectors
antennaSO-239
micmicrophone connector
keykey jack
psuexternal power supply connector
ext spkrexternal speaker
accaccessory connectors
power reqExternal PSU: Collins 516F-2 (AC) or PM-2 (mobile). Also compatible with 312B-4 console.
THE classic, Collins' legendary SSB transceiver, first amateur mobile SSB, 24,000+ units built first commercially available amateur mobile SSB transceiver (KWM series pioneered this!) SSB and CW ONLY (no AM, no FM) filter-type SSB generation (unsurpassed for the era) double-conversion receiver: crystal-controlled HF conversion + VFO-controlled LF conversion HF IF: 200 kHz flat response (2.955-3.155 MHz) + LF IF: 455 kHz standard 200 kHz band segments selected by crystals (supplied for 80/40/20/15m + WWV calibration) KWM-2A: additional crystal board for 14 optional crystals including MARS/non-amateur frequencies automatic load control (ALC): keeps signal at rated PEP, increases average talk power 10 dB RF feedback around PA and driver (improved linearity) 10 dB ALC compression on IF and RF amp stages receiver sensitivity: 0.5 µV for 10 dB S/N selectivity: 2.1 kHz at -6 dB / 4.2 kHz at -60 dB AGC: fast attack, slow release, <20 dB output change from 5 µV to 1V input modified break-in CW with sidetone monitoring noise blanker 25 kHz calibrator dual-role circuits: many tubes and tuned circuits serve BOTH transmit and receive (compact design!) light gray enamel + simulated leather front panel (matches S-Line) external power supply required: 516F-2 (AC) or PM-2 (mobile, limited duty cycle) frequency stability: better than 100 c/s per hour (remarkable for the era!) dial accuracy: readable to 1 kHz KWM-2A widely used by MARS stations in Vietnam (phone patches home for US troops!) over 24,000 units manufactured, last Collins tube-equipped amateur transceiver KWM-2: 1959 / $1,150. KWM-2A: 1961 / $1,250 combined Collins 75S-1 receiver with 32S-1 transmitter in one box VINTAGE. DISCONTINUED. Replaced by KWM-380. 80-10m in 200 kHz crystal-selected segments 0.5 uV sensitivity, 2.1 kHz selectivity ALC + 10 dB RF feedback, ~100 Hz/hr stability 24,000+ built; KWM-2A adds MARS crystals
Strengths

Collins' classic SSB/CW transceiver and the first amateur mobile SSB transceiver. Filter-type SSB, ALC and RF feedback for clean transmit, 0.5 uV sensitivity, and good frequency stability (~100 Hz/hour). About 100W output (175W PEP input). Over 24,000 were built.

Weaknesses

SSB/CW only (no AM/FM). Tubes need maintenance. Requires an external power supply (516F-2 or PM-2). Bands are crystal-selected in 200 kHz segments, with no general coverage and no WARC bands without extra crystals. Heavy as a set (~25 kg with PSU).

Verdict

The transceiver that popularized SSB. The KWM-2 was the first amateur mobile SSB transceiver, combining a 75S-1-class receiver and 32S-1-class transmitter in one box. Filter SSB, ALC, RF feedback, and solid stability made it a benchmark; KWM-2As served MARS stations during the Vietnam era. Over 24,000 were built before the solid-state KWM-380 replaced it.

The Collins KWM-2 is one of the most revered transceivers in amateur radio history, a compact, beautifully engineered HF radio from Collins Radio that set the standard for build quality and performance when it appeared at the end of the 1950s. It covers the 80 through 10 meter bands in SSB and CW, with a power input of 175 watts PEP on sideband (160 watts on CW) for a nominal 100 watts of output, all in a package small enough for mobile use.

Collins built the KWM-2 to a standard the amateur market had never seen: mechanical filters for superb selectivity, rock-solid mechanical construction, and the legendary stability that made Collins gear the choice of militaries and broadcasters alike. The later KWM-2A added coverage of additional 10-meter segments. Used examples remain prized heirlooms, and the KWM-2 is widely regarded as a high-water mark of the vacuum-tube transceiver era.

It is a discontinued classic. See the matched 32S-3 transmitter and 75S-3 receiver of the Collins S-line.