SW-3

A highly efficient and popular receiver for amateur use, with telephone receiver output. The choice of leading amateurs the world over. This new three-tube Ham receiver bristles with original and ingenious features. Its efficiency and ease of handling will be a revelation to everyone who employs it.

FEATURES

  • Special Shielding in the SW-3 is the result of careful research and is one of the reasons for it's remarkable efficiency!

  • Single control with a set and forget antenna trimmer!

  • Calibrated attenuation control!

  • Full A.C. model!

  • High signal-to-noise ratio!

  • Band-spread coils standard equipment!

  • Real gain in RF stage!

  • Smooth sensitivity control!

  • Universal voltage model!

  • Compact-adaptable to portable, aircraft and boat use!

  • The price is right!

    POWER SUPPLY

    For complete a.c. power of the receiver, it is suggested that a power pack be used. The power unit employs a Type '80 tube as a rectifier, an r.f. filter and a 2 section hum filter. The power transformer, in addition, is equipped with an electron static shield between the secondaries and the 110-volt winding, thus not only preventing any r.f. disturbances originating in the power supply from getting into the receiver, but also preventing disturbances originating in the rectifier tube from causing trouble. A unique feature of the battery model is its design to use either battery or a.c. type tubes. When used purely as a battery operated receiver, then the new 6-volt 5-prong heater Type '36 and '37 tubes are recommended so as to permit operation form the standard 6-volt storage battery or "A" eliminator. When using the battery model with the combination a.c. - d.c. power supply, a common center-tap resistor should be connected across the heaters inside the base of the chassis.

    OUTPUT CIRCUITS

    In a receiver designed with the peculiar requirements of amateur operation in mind, there is little necessity for audio amplification of loudspeaker magnitude. The concentration desirable for communication reception, particularly of weak signal through interference and QRN is achieved with less effort when ear 'phones are used. The power amplifying stage has therefore been omitted in the design of the SW-3.The high amplification factor, high transconductance and the plated plate impedance characterizing the new tubes have enabled the engineer to achieve a degree of sensitivity and selectivity that has heretofore been little more than experimental ideals.

    CONTROLS

    The "set and forget" antenna trimmer control is at the left of the front panel and the regeneration control on the right, with the operating edge of the calibrated volume control disc immediately below the main tuning dial.

    COILS

    Following the policy of careful attention to all details of a simplified circuit, in order to secure maximum performance a special molding material was selected for the transformer forms. The use of this low-loss material permits the winding of the coil turns into grooves turned into the solid walls of the forms, thus resulting in a rigid transformer that will stand up under quite rough handling. The band-spreading is quite simple, the variable tuning condenser, now shunts only a portion of the total inductance while the grid lead and the condenser connect directly to the top of the coil. Finally, the trimmer condenser shunts this whole arrangement and is in parallel with the tube capacity, connecting directly from the grid to the filament.

    PRICES

    ACSW3 National complete 3-tube Short Wave Trill Box - less coils - less tubes - wired by the Jackson Research Laboratories List Price $29.50

    Coils for the ACSW-3
    Range List Price Per Pair
    9. to 15. meters $5.00
    13.5 to 25. meters 5.00
    23. to 41. meters 5.00
    40. to 70. meters 5.00
    65. to 115. meters 5.00
    115. to 200. meters 5.00
    200. to 360. meters 5.50
    350. to 550. meters 5.50
    500. to 850. meters 6.50

    Source: 1931 issues of QST

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