ASK (Amplitude Shift Keying)
ASK is the family of modulation in which binary information is transferred by changing the amplitude level of the carrier. The transmitter and receiver circuits are simple and consumption is low; on the other hand, since noise also arrives via amplitude, the error rate rises quickly when the ambient noise floor goes up. It is common in cheap short-range remote controls.
An ASK receiver follows the envelope of the carrier and counts anything above a certain threshold as one and below it as zero. This threshold may be fixed or floating; in either case the decision mechanism depends directly on amplitude.
- Advantage: an envelope detector can be built with a few passive components, the transmitter merely switches the carrier, and average current falls.
- Weak point: arcing, contactor sparking and switch-mode supply noise are broadband and amplitude in character; the receiver may mistake them for data.
- Result: at the same output power, a lower effective range is obtained than with an FSK link.
The field symptom is typical: the remote works fine in an empty workshop, and commands start dropping when a welding machine or a frequency inverter comes on. The solution is usually to manage the noise floor rather than the range; shielding the motor cable, moving the antenna position away from the noise source and adding a filter on the supply line all give measurable gains on ASK-based links.
Context in which this term is used: Wireless remote control installation: pairing, relay, safety