A Spectrum Analyser display shows all the frequencies between 5 and 28 MHz. In order to avoid possible interference to other services, those frequencies which are known to be permanently allocated to fixed broadcasting and telecommunication stations are locked out, as well as frequencies which happen to be used at any instant so that they can also be avoided by the OTHR transmitter. GLOSSARY for non-technical readers. A.M. A mode of modulation (amplitude). A.R.R.L. Amateur Radio Relay League (U.S.A.). Beacon Transmitter radiating identification signal. C.Q. General call, to any station. C.R.T. Cathode ray tube (like TV screen). C.W. Continuous wave (mode of sending telegraphy). Callsign Station identification (letters & numbers). Coherer A device for making radio frequencies audible. DE Morse abbreviation for 'from' (French). DX Communication over a long distance. Detector Any device for making radio frequencies audible. Doppler shift Change in pitch (of sound) or frequency of a (radio) wave E.D.E.S. Initials of a war-time Greek guerrilla organisation. E.E.R. Equivalent Greek initials for R.A.A.G. (q.v.) E.L.A.S. Initials of a war-time Greek guerrilla organisation. E.L.F. Extremely Low Frequency. E.M.E. Earth-moon-earth. Also Moonbounce q.v. H.H.M.S. His Hellenic Majesty's Ship. Gasfet A type of transistor. KHz Kilohertz--international unit for kilocycle. M.U.F. Maximum usable frequency. MHz Megahertz--international unit for megacycle. Moonbounce Communication by reflection from the moon. OTHR Over-the-horizon radar. Q code Abbreviations used when communicating by telegraphy. Q1 Unreadable. Q2 Barely readable--only some words. Q3 Readable with considerable difficulty. Q4 Readable with practically no difficulty. Q5 Perfectly readable. QRO High power. QRP Low power. QRT "Stop sending". Frequently used for "shut up". QSO Two-way communication. QST Call to all stations. Also title of journal of the A.R.R.L. QTH Location or address of a station. R.A.A.G. Radio Amateur Association of Greece. R.F. Radio frequency. R.S.G.B. Radio Society of Great Britain. RST System of reporting readability, strength & tone of a signal. RX Receiver. S unit Unit for reporting strength of received signal. S.I. unit International system of definitions. SSB Single side-band--a mode of modulation. SWL Room where radio equipment is set up. Shack Room where radio equipment is set up.