Transcript Antennas & Propagation

Antennas & Propagation
A mixed bag from VLF to VHF
Brian Austin G0GSF
The First Antenna?
…and The First Radio Signals?
Marconi’s antenna 1896
Oliver Lodge’s Biconical 1897
Marconi’s monster 1901
Ground Waves
The EM Spectrum
ELF=30 to 300 Hz
Submarine propagation
Project ‘Sanguine’ USN 1970s
Carrier frequency
Submarine depth
Range
RX antenna length
TX antenna length
Resistance: TX antenna
Radiation resistance
Radiation efficiency
Antenna current (peak)
TX power
Data rate
45 Hz
250m
6200 miles
300m trailing wire
1000km (total wire in grid)
44 ohms
0.012 ohms
0.027%
1095 amps
26.4MW
1 bit/s
Transmitting to Submarines
Arboreal Aerials
The HEMAC
Trees as transmitters
• TX frequency: 450kHz
• TX power: 35W
• TX range: 35miles
CW; 15miles AM.
• And it was directional!
Tree-to-Tree
• TX frequency: 4.65MHz
• TX power: 15W CW/SSB
• Horizontal RX
antenna better than
vertical!
Coupling through Forests
Radio Underground
SSB Underground
NVIS propagation
NVIS & the Ionosphere
Spot the NVIS antenna
NVIS Loop Antenna
Sporadic E at HF
Louis Varney’s aerial
G5RV performance
www.karinya.net/g3txq/g5rv/
Band
Lowest SWR
Worst SWR
160
>100
>100
80
3.2
12.6
40
4.9
5.9
30
48
50
20
2.5
3.7
17
32.1
33.6
15
6.1
12.9
12
3.6
4.6
10
51
60
The ‘ZS6BKW’ multiband
Centre SWR BandHF
width
Band Freq. (min)
(MHz)
(kHz)
40
7.10
1.1:1
360
20
14.20 1.1:1
270
17
18.10 1.3:1
380
12
24.92 1.4:1
260
10
28.97 1.4:1
400
Yagi Uda Array
V-shaped Yagi
… and in conclusion