Frequency Drift

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A Frequency Drift is an offset measure of an oscillator from its reference frequency.



References

2016

On a radio transmitter, frequency drift can cause a radio station to drift into an adjacent channel, causing illegal interference. Because of this, Frequency allocation regulations specify the allowed tolerance for such oscillators in a type-accepted device. A temperature-compensated, voltage-controlled crystal oscillator (TCVCXO) is normally used for frequency modulation.
On the receiver side, frequency drift was mainly a problem in early tuners, particularly for analog dial tuning, and especially on FM, which exhibits a capture effect. However, the use of a phase-locked loop (PLL) essentially eliminates the drift issue. For transmitters, a numerically controlled oscillator (NCO) also does not have problems with drift.
Drift differs from Doppler shift, which is a perceived difference in frequency due to motion of the source or receiver, even though the source is still producing the same wavelength. It also differs from frequency deviation, which is the inherent and necessary result of modulation in both FM and phase modulation.