Collins 75A-1
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| Frequency | RX: 80–10 m amateur (80/40/20/15/11/10 m segments, 3.2–30 MHz) |
| Power | Receiver only |
| Modes | AM, CW |
| Weight | 25.9 kg (57.1 lb) |
| Connector | 300 Ω balanced antenna terminals |
| Year | 1947 |
| antenna | 300 Ω balanced antenna terminals (accepts balanced or unbalanced wire) |
| speaker | 4 Ω and 500 Ω speaker terminals |
| headphones | low-impedance headphone output |
The first Collins receiver designed specifically for amateur radio (1947, $375). It was the first fully permeability-tuned amateur receiver, introducing the Collins PTO for backlash-free, linear, rock-stable tuning. Fourteen-tube dual conversion with a variable-bandwidth crystal filter in the 500 kHz second IF. Built to Collins commercial standards.
It uses a step-variable crystal filter rather than the sharper mechanical filters of the later 75A-2/A-3/A-4. Very heavy and large at about 57 pounds. Its 300-ohm balanced antenna input suits the wire antennas of its day more than modern 50-ohm coax. As the first of the line, it was soon superseded by its more refined successors.
Where the Collins amateur legacy began. Not as refined as the later 75A-4 or the 75S series, but historically important as the foundation of the 75A line. A clean 75A-1 is often cheaper than its successors because fewer collectors chase it.
The Collins 75A-1, introduced in 1947, was the receiver that launched Collins' celebrated 75A series and helped define the modern amateur communications receiver. It is a receive-only set covering the amateur bands from 80 through 10 meters (including 40, 20, 15, and 11 meters) built as a fourteen-tube dual-conversion superheterodyne with a crystal-controlled first oscillator and a multi-position crystal filter that narrows selectivity in five steps from about 4 kilohertz down to a remarkably sharp 200 hertz, receiving AM and CW.
For the late 1940s it was a sophisticated and beautifully built receiver. It was the first completely permeability-tuned amateur receiver, using Collins' precision PTO for backlash-free, linear tuning and rock-solid stability, Collins marketed it as "the first really new amateur receiver since the advent of the superheterodyne." The design language and reputation it established would carry forward through the 75A-2, 75A-3, and the legendary 75A-4.
A few details mark it as a product of its era: it is a big, heavy boat-anchor of about 57 pounds in a steel cabinet, it feeds from a 300-ohm balanced antenna line rather than modern 50-ohm coax, and its band switch even included a 15-meter position before that band became available to U.S. amateurs in 1952. As the first of the line, a clean 75A-1 holds a special place for collectors of early Collins equipment.
It is a discontinued classic, produced from 1947 to 1950. See the later 75A-4 and the 32V-3 transmitter.