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 1970sCarrier frequency 45 Hz

Submarine depth 250m

Range 6200 miles

RX antenna length 300m trailing wire

TX antenna length 1000km (total wire in grid)

Resistance: TX antenna 44 ohms

Radiation resistance 0.012 ohms

Radiation efficiency 0.027%

Antenna current (peak) 1095 amps

TX power 26.4MW

Data rate 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 performancewww.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

HF

Band

Centre

Freq. (MHz)

SWR

(min)

Band-width

(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