Download - Wave probigation
WAVE PROBIGATION
Overview
Waves and ionisation Atmosphere Ionosphere Troposphere Other methods
Radio Waves
Electromagnetic energy Models
Waves Particles
Electrical part Magnetic part
Polarisation Vertical Horizontal
Ionisation
Ion Protons != electrons
Ionisation Removal or addition of an electron Energy
Atmosphere
Atmosphere
Troposphere Ground to 7-17 km out - Temp dec. with
height 80% of the mass
Stratosphere About 51 km out – Temp inc. with height
Mesosphere 80-85 km out – temp at – 85 deg C
Thermo sphere 350 – 800 km out – temp +1 500 Deg C
Exosphere
Atmosphere
Troposphere Thermo sphere Exosphere
ionosphere
Ionosphere
Ionosphere
100 – 300 km Ionisation of particles
Sun Thin atmosphere Shell of electrons Layers
Radio propagation “acts like a mirror” At certain frequencies
Ionosphere
Ionosphere
D layer Ionising NO (some N2 and O2)
Electron collision high Results in blocking of HF radio waves
< 10 MHz Almost disappears after sunset
HF can pass through if broadcasted directly up
Ionosphere
E (Heavyside) layer Ionisation of O2
Refracts radio waves < 10 MHz Nordic area
At night, increasing height inc. range Es layer
Sporadic – best during the summer Refracts up to 50 Mhz
Distance of 1000 km
Ionosphere
F (Appleton) layer Ionising of O – dense Refracts most HF radio waves (3-30 MHz)
Skywaves
F1 and F2 layers Exist during the day
Ionosphere
Fading Changes in the ionosphere Changes the polarisation
Angle Critical angle
Depends on ionosphere and frequency used Hi angle and Hi F pass through.
Using the Ionosphere
Using the Ionosphere
Nordic region 3.5 – 7 MHz Dipole
Straight out Using D layer
14 – 30 MHz Uses E and F layers (low elevation angle) 2 000 – 4 000 Km
Using the Ionosphere
DX traffic DX – distance Dipole or yagi array For Europe
30 Deg 0.5 Wave length
Out side Europe 1 -2 X wave length 10 Deg 1.5 X wave length
Troposphere
Its damp! 99% of the water vapour! Effects radio transmissions
Hi F = more absorption Used for VHF, UHF and SHF transmissions
Line of sight 20- 30 km (depends on power)
Can scatter (refraction) Up to 2 000 km
Other Methods
Earth-Moon-Earth (EME) 144 MHz, 434 MHz and 1 296 MHz As far away as Australia!
Meteors Same as EME Short burst
Auroras > 25 MHz NW -> NE aerial
Questions?