Definition
In a crystal-controlled radio transmitter or receiver, the controlling crystal constant is the fixed multiplier that relates the natural resonant frequency of the quartz crystal to the final operating frequency of the equipment. The crystal vibrates at one frequency, and that frequency is then multiplied through a chain of stages to produce the higher transmitted or received frequency. The constant is the multiplication factor used in that process.
Plain English
A fixed number used to figure out what radio frequency a piece of equipment will operate on, based on the frequency of the small quartz crystal inside it. The crystal vibrates at one frequency; the equipment multiplies it by this number to get the working frequency.
Context Anchor
Seen in older aircraft radio maintenance, especially when selecting, checking, or replacing channel crystals in crystal-controlled communication or navigation radios.
Derivation
Crystal here refers to a small piece of quartz that vibrates at a very precise frequency when electricity is applied. Constant means a fixed value that does not change. Together: the fixed multiplier tied to a specific controlling crystal.
Why Pilots Care
It keeps aircraft communication and navigation radios locked on the correct frequencies for reliable signal transmission and reception.
Intuition Check
Do not read “constant” as one universal number for every radio. Here it means a fixed value for a specific radio design or crystal calculation.
Example Sentence 1
The technician calculated the transmitter's output frequency by multiplying the crystal's resonant frequency by the controlling crystal constant.
Example Sentence 2
Frequency drift was traced to an incorrect controlling crystal constant in the oscillator circuit.