Note
QST, Oct 1947, p. 121.
QST, Nov 1947, inside front cover.
Lafayette-Concord catalog "1948 Christmas Book," p. 34.
See National's Notes: QST, Jun 1949, p. 73.
Lafayette-Concord (1949 #949), p. 144.
Allied Radio catalog 1951 (copyright 1950), p. 140.
QST, Mar 1951, p. 97. ("last call")
Introduced by the National in November 1947, the NC-57 was designed as a streamlined, mid-sized, medium-priced superheterodyne receiver to counter competition from the Hallicrafters S-40. Originally priced at $89.50, it offered an extended tuning range in a dramatically downsized cabinet compared to National's bulky pre-war offerings.
The standard NC-57 is a 5-band, 9-tube receiver covering a continuous frequency range from 0.54 to 54 MHz, notable for including the 6-meter amateur band which was typically reserved for higher-end rigs. The model number "57" is widely attributed to its 5 tuning bands and 7 active signal tubes (excluding the rectifier and voltage regulator).
Tube Lineup
– RF Amplifier: 6SG7
– Frequency Converter: 6SB7Y
– IF Amplifiers: Two 6SG7s
– 1st Audio / BFO: 6SL7 (Note: Some early chassis variants have "6SN7" stamped and inked out)
– Detector / AVC / Noise Limiter: 6H6
– Audio Output: 6V6
– Voltage Regulator: 0D3
– Rectifier: 5Y3
Front Panel Controls: Includes RF gain, AF gain/power, tone, band switch, send/receive, a multi-position mode switch (CWO/MVC/AVC/ANL), pitch control, and a highly effective antenna trimmer. A front-panel headphone jack draws audio directly from the output transformer.
The main tuning dial is robustly gear-driven for high accuracy and positive action, while the bandspread dial relies on a dual-dial cord and counterbalance system (which is prone to minor backlash).
Rear Chassis: Includes antenna/ground terminals and two auxiliary octal sockets. One serves as an accessory/phono input, while the other features a jumpered plug for standard AC operation that can be rewired for remote switching or portable 6V battery/B+ emergency power.
Production Variants
NC-57B: Mechanically identical to the original but features revised accessory socket wiring to allow direct plug-in of matching vintage accessories like the SM-57 S-meter and the SOJ-3 Select-O-Ject audio filter.
NC-57C: A specialized long-wave variant tuning 0.19 to 0.41 MHz alongside a slightly altered shortwave coverage of 0.54 to 34 MHz.
NC-57M: A dedicated marine version redesigned with an AC/DC transformerless circuit. It replaces the audio output and rectifier with a 25L6 and 25Z6, and omits the rear accessory sockets entirely.
