Benutzer-Werkzeuge

Webseiten-Werkzeuge


en:e-616

E-616: National NC - 100 XA

E-616, All Wave Receiver NC - 100 XA; developed and produced by National Company Inc., Malden, MA.

The NC-100A is a successor to the famous National HRO: the set somes no longer with plug in coils, they are installed in a „coil catacomb“ in the bottom part of the receiver and are moved mechanically to the correct position.

E-616: National NC-100XA

Technical Data

Power Supply

Dimensions

  • 438 x 272 x 298 mm

Accessories

The original speaker which matches the NC-100 has an impedance of 500 ohms, designation of the receiver together with the external speaker is NC-100 XSA .


Operation

The big tuning knob is located in the center of the front panel, above it the semicircular frequency dial. A mechanically driven dial pointer points to the dial corresponding to the frequency band; in contrast to the HRO, the frequency dial is calibrated so the frequencies can be read directly on the NC-100A. Similar to the HRO, there is also a logging dial with 0 - 1000 divisions to retune known stations using a frequency logging chart.

The coil sets are located in the bottom of the receiver in a kind of coil drawer (which is called „Coil Catacomb“), they are moved to position and switched with the lower large rotary band selector knob, after one revolution the knob locks in the next frequency range position.

Left to the frequency scale, the signal strength meter and the operation switch is located. It has three positions: OFF (receiver turned off), B + OFF (tubes heated, no plate voltage B+) and B + ON for operation.

Just below it is the RF Gain control for the RF amplification. In the left lower corner, the controls for the NOISE LIMITER (turned off in position 0) and the tone control are located.

To the right of the frequency dial, there switches for automatic volume control (AVC), for manual gain control MVC and a third position for CW reception with manual gain control and activated BFO. The BFO pitch can be adjusted with the CWOSC. control.

The AFGAIN CONTROL knob at the right of the frequency dial acts as volume control.

Technical Principle

Technically speaking, the NC-100A is a single conversion superhet with a RF preamplifier: the signal from the antenna is fed to the RF amplifier stage (V-101: 6K7). With the oscillator signal (V-103: 6J7) it is converted to the intermediate frequency of 456 kHz in the mixer stage (V-102: 6J7). Then, the IF signal is amplified in two IF stages (V-104: 6K7 / V-105: 6K7) and fed to the V-107 (6C8G) for demodulation, it's second system is used for the noise limiter. After a audio preamplifier (V-106A: 6F8G, the second system of the tube is used for the AVC), the signal is fed to the AF final stage 6V6G (V-109).
A speaker with an impedance of 600 ohms can be connected to the receiver directly, to drive a modern low-impedance speaker, an output transformer is necessary.

For A1 / CW reception the signal of the Beat Frequency Oscillator (V-108: 6J7) is fed to the IF before demodulation. In contrast to the HRO receiver, the set comes with a built-in power supply; a 5Z3 acts as rectifier tube (V-110).

Valve setup

V101 (6K7, RF preamplifier); V102 (6J7, mixer); V103 (6J7, oscillator); V104 (6K7 , 1st IF amplifier); V105 (6K7, 2nd IF amplifier); V106 (6F8G, AF preamp, AVC); V107 6C8G, demodulator, limiter); V109 (6V6G, AF final amplifier); V108 (6J7, BFO).
V110 (5Z3, mains rectifier).

Development

The NC-100 was developed as a successor to the legendary HRO, the coils in the NC-100 are moved in the „coil catacomb“ in a drawer-like arrangement. The NC-100A as the successor of the original NC-100 came with a direct readout frequency dial instead the dial of the NC-100 which like the HRO still relied on a micrometer logging dial and a frequency conversion chart.

Field use

Several receivers from National are found in a list of Swiss Army receiving equipment, most of them were acquired in very small numbers for special purposes.
Apparently different variants of the National NC-100A were used, the NC-100XA comes with a crystal filter, the NC-100 XSA the same with the matching external loudspeaker.

  • E-616 : National NC-100 XA (with quartz filter)
  • E-617 : National NC-100 XSA (with quartz filter and external speaker)
  • E-618 : National NC-100 A (basic model with directly readable frequency dial instead of HRO dial)

Manuals

Additional information

en/e-616.txt · Zuletzt geändert: 2019/03/31 09:38 von 127.0.0.1