NC-80X NC-81X

The NC-80X is a ten tube superheterodyne covering frequencies from 540 to 30,000 kilocycles in four ranges. The NC-81X employs the same circuit but is fitted with a special tuning condenser and special coils to provide full band spread on the 10, 20, 40, 80 and 160 meter amateur bands; frequencies between these bands cannot be covered.

FEATURES:

  • Employs the same type of movable tuning unit used so successfully in the NC-100, and which combines high electrical efficiency with plug-in coil convenience.

  • Do to the use of a high IF frequency (1560 KC) image frequencies are so far apart that they can be effectively rejected without a preselector.

  • The linear scale is calibrated directly in megacycles for all coil ranges.

  • The tuning system employs an automatic dual-range control, depending on the speed you are tuning it automatically shifts between a eleven to one and a fifty five to one tuning ratio.

    TUBE COMPLIMENT:

    1st Detector 6J7
    High Frequency Oscillator 6K7
    1st I.F. 6K7
    2nd I.F. 6K7
    3rd I.F. 6K7
    2nd Detector 6C5
    AVC 6B8
    Beat Frequency Oscillator 6J7
    Power Output 25L6G
    Rectifier 25Z5

    The battery models have no rectifier tube and employ a Type 6V6G output tube instead of the 25L6G.

    CIRCUIT: The circuit consists of a first detector and oscillator employing separate tubes, three stages of I.F. amplification, a bias type power detector and a resistance coupled beam power output stage; maximum undistorted audio output is 2 1/2 watts. A separate tube is employed to provide amplified and delayed AVC and a separate beat frequency oscillator is coupled to the 2nd detector for c.w. reception.

    TUNING SYSTEM: The tuning system is of an entirely new design and employs a multiple-scale dial of the full-vision type, accurately calibrated in megacycles. Several unusual features are incorporated, such as the mirror, for overcoming parallax, the auxiliary linear scale, numbered from 0 to 100, and six adjustable frequency markers by means of which any particular stations or frequencies may be "logged" on the dial itself. A dual vernier reduction drive is used which provides a 55 to 1 reduction over any narrow band of frequencies with automatic shift to an 11 to 1 reduction for conveniently and rapidly moving the pointer to another section of the scale.

    CRYSTAL FILTER: Provides continuously variable selectivity over a range of from 300 cycles to 7 kilocycles.

    OUTPUT CIRCUIT: The output terminals of the receiver are connected in the plate circuit of the 25L6G power output tube. The speaker terminals are at the rear of the chassis. A headphone jack is mounted at the rear of the chassis and is wired in such a manner that the speaker is quiet when the headphones are in use.

    POWER SUPPLY: The power supply is of the 110-120 volt AC-DC type, except in models designed for 220-240 volt operation and certain other special services, such receivers being equipped with a suitable built-in power transformer.

    Battery models are designed for 135 volt operation with a 6-volt heater supply. The receiver is fitted with a suitable cable and plug for making the connections. The B-supply drain is approximately 35 milliamperes, while the heater current is 2.8 amperes.

    PRICE LIST:

    NC-80X Receiver, complete with tubes, crystal filter, 8" PM speaker chassis, etc. for 115v. AC or DC List Price, $146.65
    NC-81X Receiver, Amateur Model, complete with tubes, crystal filer, 8" PM speaker chassis, etc. for 115v. AC or DC List Price, $146.65
    Type DSC-8G Metal Cabinet for 8" speaker, same finish as receiver List Price $8.00

    Note: Either of the above receivers can be supplied modified for Battery Operation 6v. heater, 135v. B-supply.

    Source: The National NC-80X, NC-81X instruction manual, 1937 QST's

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