Baby Superhet

Designed by prominent receiver authority W. T. Cocking and published in Wireless World in August 1932, the "Baby Superhet" was a milestone in British home-constructor receiver design. It brought high-selectivity superheterodyne performance to constructors at a time when European broadcast band congestion overwhelmed standard tuned radio frequency (TRF) sets.

Following the initial success of the A.C. mains-powered model, a companion Battery-operated version followed in October 1932, expanding the accessibility of the design for rural or off-grid constructors without access to mains electricity.

Key Technical Features & Architecture:

• Single-Valve Frequency Changer: Utilised an AC/Pen pentode in a novel self-neutralising circuit that combined oscillator and mixer functions without causing radiation or interaction with the pre-selector.
• Pre-Selector & I.F. Bandpass Filtering: Incorporated an inductively-coupled two-stage input bandpass filter before the frequency changer, followed by two variable-coupling 110 kHz I.F. bandpass transformers (Wearite Type W.W.I.F.).
• Automatic Tone Correction: Engineered inherent high-frequency compensation into the pentode output stage to restore treble frequencies attenuated by the narrow-passband I.F. stages, eliminating the need for complex tone-control networks.
• Power & Smoothing: Used a Westinghouse HT9 metal rectifier in a voltage-doubling circuit providing ~360 V D.C., with H.T. smoothing accomplished directly by passing total H.T. current through the 2,500 Ω field coil of the internal moving-coil speaker.
• Gramophone Integration: Included dedicated pick-up terminals and a Radio-Gramo switch that reconfigured the 2nd detector (354V) as an audio amplifier

Vous pourrez trouver sous ce lien 9 modèles d'appareils, 5 avec des images et 6 avec des schémas.
Tous les appareils de Wireless World; London