Definition
The grid in a pentode vacuum tube, located between the screen grid and the plate, that is held at a low (usually zero or slightly negative) voltage to repel secondary electrons knocked loose from the plate back toward the plate, preventing them from reaching the screen grid and degrading tube performance.
Plain English
An extra wire mesh inside an older-style vacuum tube that pushes stray electrons back where they belong, so the tube works cleanly.
Context Anchor
Seen in descriptions of older aircraft radios, transmitters, receivers, and other vacuum-tube electronic equipment.
Derivation
From Latin 'supprimere,' meaning to press down or hold back. The grid 'suppresses' unwanted secondary electrons by pushing them back toward the plate.
Why Pilots Care
Pilots flying aircraft with legacy radio or instrument equipment may encounter vacuum tube terminology in maintenance manuals or troubleshooting discussions; understanding what each grid does helps when reading technical descriptions of how the gear works.
Intuition Check
Do not think of grid here as an electrical power grid. In this term, a grid is a small wire electrode inside a vacuum tube.
Example Sentence 1
The suppressor grid in the pentode prevents secondary electrons from the plate from interfering with the screen grid.
Example Sentence 2
Proper suppressor grid bias keeps the tube operating without signal distortion.