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Lessons in Wireless Telegraphy

Chapter 24: LESSON TWENTY-ONE. ANCHOR GAPS.
By Alfred Powell Morgan
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About This Book

This work presents a compact, lesson-based introduction to the physical principles behind wireless telegraphy, aiming to give operators a clear theoretical grounding. Arranged in discrete lessons, it starts with magnetism, magnetic induction, and basic electrochemical cells, then develops circuit laws and the components and methods for producing, radiating, and detecting electromagnetic signals. Emphasis is on clear explanations, illustrative diagrams, and simple experiments to show how transmitters, receivers, antennas, and tuning interact, while detailed engineering and maintenance procedures are deferred to a companion volume.

LESSON TWENTY-ONE. ANCHOR GAPS.

Certain types of aerial switches require the use of what is known as an anchor gap.

An anchor gap consists of a small insulating ring, usually hard rubber, having two and sometimes three electrodes set in the periphery and almost touching each other at the sparking points.

Anchor gaps having two electrodes are used in the aerial circuit of most Break-in-Systems to prevent the receiving currents from flowing directly into the ground through the transmitter without passing through the detector.

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FIG. 44. Anchor Gaps.

A Break-in System enables the operator to hear the signals of any other station which may be transmitting at the same time when he is operating his own key.

The three-electrode anchor gap is commonly used on loop aerial systems. Two of the points are connected to the aerial, one to each half and the other to the lead from the helix. The high potential currents from the helix easily leap across the little gap and divide between the two halves of the aerial.