Propagation
Why a frequency gives a different result at midday than at night.
- Bodenwelle
- follows the earth's surface, carries far on long wave and 160 m
- Raumwelle
- is refracted in the ionosphere and comes back down far away
- D-Schicht
- lowest layer at 60 to 90 km altitude, only present by day, mainly absorbs the low bands
- E-Schicht
- lower layer, present by day, attenuates low frequencies
- F2-Schicht
- the decisive layer for long-distance contacts on HF
- Sporadic E
- short-lived clouds in the E layer, open up 6 m and 2 m for long distances in summer
- MUF
- highest usable frequency for a path
- LUF
- lowest usable frequency, below it absorption eats the signal
- Skip-Zone
- dead zone between the end of the ground wave and the first hop
- Grayline
- twilight line, along which contacts work particularly well
- Sonnenfleckenzahl
- rough measure of solar activity, a high value helps the high bands
- Solarflux, A- und K-Index
- indices for solar radiation and disturbances of the earth's magnetic field
- Aurora
- reflection off the aurora, distorts the audio heavily
- Ionosonde
- transmitter that sends straight up and measures the height and critical frequency of the layers from the echoes
- foF2
- critical frequency of the F2 layer at vertical incidence, measured by the ionosonde
- MUF(3000)
- MUF for a 3000 km hop, roughly three times foF2
- hmF2
- height of the densest part of the F2 layer, usually 250 to 400 km; the higher it is, the longer the hop
- Sprungweite
- distance after which a ray reaches the ground again after one reflection; via the F2 layer at most about 4000 km
- Abstrahlwinkel
- angle above the horizon at which an antenna radiates; low angles hop far, steep ones short
- Sekantengesetz
- at oblique incidence a ray still turns back at a higher frequency than at vertical incidence: f = foF2 / cos of the angle of incidence
- foEs
- critical frequency of a sporadic E cloud at vertical incidence; from about 10 MHz 6 m opens over about 2000 km
- Kp-Index
- disturbance of the earth's magnetic field per three hours, averaged worldwide, 0 to 9; from 5 it counts as a storm
- Bz
- north-south component of the magnetic field in the solar wind; if it points south (negative) for a long time, it couples to the earth's magnetic field and things get unsettled
- Sonnenwind
- stream of charged particles from the sun, normally around 400 km/s; fast and dense it disturbs the earth's magnetic field
- Flare-Klasse
- strength of a solar X-ray flare: A, B, C, M, X, each letter ten times stronger; from M upwards HF drops out briefly on the daylight side
- D-RAP
- NOAA map showing up to which frequency the D layer currently absorbs 1 dB
- Tropo
- extended range on VHF/UHF due to temperature inversions
Related
More sections in the glossary
Q codes Abbreviations in telegraphy RST report Phonetic alphabet Callsigns in Germany Law and administration Regulation and radio policy DARC, DOK and awards Portable programmes Repeater operation Modes Propagation Shack technology