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?