Technicals terms  R ... T

Relay station

Voice repeater station, receives on one frequency and retransmits on other frequency

RTTY

Radio Teletype

PSK31

Digital operating mode, narrowband text transmission, Radio Frequency range between 3-30 MHz

Shift

Difference of frequency between two signals Single Side Band Modulation, operating mode for voice

SSB

communication where the carrier and the other sideband is suppressed (much more efficient than AM)

TNC-Modem

(Terminal Node Controller), Electronic equipment used for Packet Radio. Performs modulation and demodulation and control functions