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management & assessment function and does not have to depend on
external sounding data。 It measures the ionosphere height continuously
and instantly selects the most appropriate frequency to use to scan the
target area； ideally in one hop。
This automatic function uses a quasi…vertical incidence sounder （QVI）
to measure the height of the ionosphere near the transmitting and receiving
sites； which as mentioned earlier can be miles apart； and a radar
backscatter sounder to measure the height of the ionosphere downrange
500 to 1；800 nautical miles away。 The incoming real…time data from these
soundings are compared with data stored in computer memory。 Once real…
time data are matched to a model of the ionosphere； the model can be used
to operate the system for the best results； based on the prevailing
propagation conditions。 The data for the ionospheric models take up more
than 200 megabytes of computer storage space。 Operators thus know when
and where to expect degraded performance。 Of course； strong solar
activity can virtually make over…the…horizon HF radar unusable。
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）。
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The dawn of amateur radio in the U。K。 and Greece ： a personal view
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。 Silent key Deceased radio amateur。
Sporadic E。 Propagation via the E layer of the ionosphere。 T。E。P。
Transequatorial propagation。 TX Transmitter。 Troposcatter Propagation via
the troposphere。 U。H。F。 Ultra high frequency。 V。H。F。 Very high frequency。
W。A。C。 Worked （contacted） all continents。 XYL Wife of a radio amateur。
YL Young lady operator。 73 Morse abbreviation for ‘‘best regards''。 Yagi A
type of antenna designed by a Japanese of that name。
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