Radio Module - Terminology

A collection of definitions so that everyone has the same interpretation.

Link (or datalink): the means of transmitting data from one place to another. In the case of the radio module a RF transmitter/receiver pair is a link (a simplex one).

Simplex:  data can only be sent in one direction.

Duplex: data can be sent in both directions.

Half-duplex: data can be sent in both directions but not at the same time.

Full-duplex: data can be sent in both directions at the same time.

Downlink: a simplex link, where the data is sent from the rocket to ground (hence "down" physically).

Uplink: a simplex link, where the data is sent from the ground to the rocket (hence "up" physically).

Telemetry: any data collected remotely. Data received from a ground receiver that was sent by the rocket is telemetry. Data sent from one module to another is also telemetry since it was collected on another module.

FSK: frequency-shift keying, a digital modulation scheme.

MSK: minimum-shift keying, a type of FSK.

ASK: amplitude-shift keying, a digital modulation scheme.

FM: frequency modulation, an analog modulation scheme.

AFSK: audio FSK, FSK modulation that generates an audio signal which is transmitted over FM (or some voice modulation). It's a popular amateur radio technique to do FSK using inexpensive hardware.

AX.25: a layer 2 protocol used for packet transmission with amateur radio.

APRS: automatic packet reporting system, a packet protocol for routing packets across multiple repeaters. Generally stacked on top of 1200 baud AFSK and AX.25. For rockets it is usually used to transmit GPS location.

RF: radio frequency, mostly used so you don't have to say radio.