Electro-Lytic Detector

Etheric’s 1909 Electro-Lytic Detector was almost certainly a commercial version of this Fessenden-style bare-point design, sold alongside other early wireless parts.

Basic construction (bare-point type):

• A small cup (often platinum or carbon) containing dilute nitric or sulfuric acid (commonly ~20%).
• An extremely fine platinum wire (Wollaston wire—a platinum core inside a silver sheath, with only the tip exposed) whose end just dips into the electrolyte.
• A small battery and potentiometer to apply a carefully adjusted bias voltage so the cell is polarized (tiny gas bubbles form on the fine wire tip, raising its resistance).
• Headphones in series.

When a radio-frequency signal arrives, it depolarizes the tip, lowering resistance and allowing a pulse of current through the headphones. The bias current then re-polarizes the cell, making it self-restoring. It could detect extremely weak signals and was one of the first detectors capable of receiving amplitude-modulated (voice/music) signals—Fessenden used it for his famous 1906 Christmas broadcast.

Practical characteristics:

• Extremely sensitive when properly adjusted.
• Required frequent readjustment of the wire depth and potentiometer.
• Sensitive to vibration, temperature changes, and strong static (which could dissolve the fine wire tip quickly).
• Not ideal for shipboard use because of motion; better suited to fixed land stations.
• Largely superseded by crystal detectors (more stable, no liquid or battery bias) by the early-to-mid 1910s, and then by vacuum-tube detectors.

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