Definition
A small feedback coil used in early regenerative radio receivers and certain oscillator circuits, magnetically coupled to the input or grid coil to feed a portion of the amplified output signal back into the input, sustaining oscillation or boosting sensitivity.
Plain English
A small extra coil placed near the main coil in an old-style radio circuit. It sends a bit of the output signal back to the input, which strengthens the signal and keeps the circuit running.
Context Anchor
Seen in aircraft electrical-system maintenance, especially when studying or troubleshooting older generator voltage regulators.
Derivation
From the verb 'tickle,' meaning to lightly stimulate. The coil 'tickles' the input circuit by feeding a small amount of energy back into it, just enough to keep the circuit oscillating or amplifying.
Why Pilots Care
Proper adjustment of the tickler coil was essential for reliable reception on early aircraft radios and ADF receivers before solid-state equipment became standard.
Intuition Check
A tickler coil is not a separate spark coil or a power source. It is a small feedback coil that helps a regulator switch sharply and steadily.
Example Sentence 1
The vintage aircraft receiver used a tickler coil to feed energy back into the input stage and improve signal pickup.
Example Sentence 2
Too much feedback through the tickler coil caused the regenerative circuit to oscillate and produce a howl.