Collins KWS-1
$$$$·
| Frequency | TX: 80–10 m (amateur) |
| TX power | 1000 W |
| Modes | USB, LSB, CW, AM, FSK |
| Weight | 95.3 kg (210.1 lb) |
| Connector | SO-239 (52 Ω coax output) |
| Year | 1955 |
| antenna | SO-239 (52 Ω coax output) |
| mic | high-impedance microphone jack (dynamic or crystal), J101 |
| key | telegraph key jack |
| phone patch | 600 Ω phone-patch input |
The companion transmitter to the 75A-4 (the 'Gold Dust Twins'). A full kilowatt input of clean SSB, CW, and AM from a pair of 4X-250B tetrodes, with single sideband generated by a Collins mechanical filter. Collins quality throughout, and the 4CX250B tubes are still readily available.
About 210 pounds across two cabinets, the RF deck plus the separate 428A-1 power-supply pedestal. Runs on 230 V or 115 V single-phase. The power-supply capacitors usually need reforming or replacement, the 4CX250B tubes and parts are expensive, and it generates significant heat. Moving it takes two people and a plan.
The transmitter that proved SSB could be clean enough for serious communications. Paired with a 75A-4, the KWS-1 was the ultimate amateur station of the 1950s and the rig that won Field Day for any club that could afford one.
The Collins KWS-1 is a legendary HF transmitter from the mid-1950s, the powerhouse half of the famous "Gold Dust Twins," paired with the 75A-4 receiver. It is a kilowatt-class transmitter for the amateur HF bands operating SSB, CW, AM, and FSK, with a final amplifier built around a pair of 4X-250B (4CX250B) tetrodes run in Class AB1 at a power input of one kilowatt, the maximum the FCC allowed at the time.
Built to Collins' professional standards, it generates its single sideband with a Collins mechanical filter and tunes with a 70E-23 permeability-tuned oscillator for the same rock-solid stability as the matching 75A-4. The exciter and RF amplifier share one receiver-sized cabinet, while the heavy high-voltage supply lives in a separate pedestal, together the two units weigh about 210 pounds. The matched pair cost over $2,500 new, roughly the price of a new car, which is exactly why they were nicknamed the Gold Dust Twins: magnificent, and unaffordable for most hams.
Genuine single-sideband capability at full legal power made the KWS-1 the aspirational transmitter of its era, and surviving examples (especially as a matched pair with the 75A-4) are among the most coveted pieces in all of vintage amateur radio. It is a discontinued classic. See its matched 75A-4 receiver and the 30L-1 amplifier.