ARDF

Amateur Radio Direction Finding(Fox Hunting)

“International Style”

Thomas KrahnKT5TK / DL4MDW

Fox Hunting Should this be stopped?

ARDF International Rules

● Find 5 hidden transmitters by using a portable receiver with a directional antenna

● The foxes must be found before a maximum time limit. Ranking: 1.) Number of foxes in time limit. 2.) Time at finish line

● The transmitters are under time control. Each TX sends for one minute its ID, then the next fox is switched on. (5 minute total cycle)

● Typically used: 80 m CW Morse code,2 m AM modulated Morse code

ARDF Fox IDs

● MOE – – – – – .● MOI – – – – – ..● MOS – – – – – ...● MOH – – – – – ….● MO5 – – – – – …..

● Long dashes good for direction finding● Count the dots to know which fox it is

ARDF Frequencies

● 80 m: 3.579 MHz (NTSC color carrier frequency) 5th fox sometimes on different frequency (homing fox)

● 2 m: 144.500 MHz (Europe), 146.565 MHz (official IARU region II)

ARDF Transmitters

● Control logic usually micro-controller● Time synchronization of all 5 foxes difficult● TX power 1 – 5 Watts● 2 m: Antenna cross dipole ● 80 m: Grounding wires,

Tent pegs, 50 ft wire● Close to the transmitter good

visible flag and punch station.

ARDF Transmitters

ARDF Receivers 2m

“Water Level” Housing

Long Version

Traditional German Version

Photos by DF1FO

ARDF Antennas 2 m2 Element HB9CV

4 Element Log Periodic

3 Element Yagi Russian Version

Moxon Rectangle

Photos by DF1FO

ARDF Receivers 80 m

ARDF Receivers 80 m

DF1FO 2010

1947

SM5IQ 1953

WB6BYU QST 9/2005

VK8YNG

OE6GC

PJ-80

ARDF Antennas 80 m

Frame Antenna:10 wire cable in circular aluminum tubeforming a coil. Circular tube must havean isolated gap! 6 dB more sensitive than ferrite rods

Photos by DF1FO

Ferrite Rods:longer = betterWatch out for surplus bars withfurrows!

Not all ferrite bars work at 3.5 MHzSelect by try & error only

ARDF Orientation Gear

● GPS usually not allowed● Compass● Map

● Appropriate sport clothing● Sturdy shoes● Carry some drink● Rope your glasses around neck

ARDF Strategy● Start with the fox with the loudest signal● Plan a round course (No zigzag)● Make sure to watch the clock and arrive at the

finish line before the max. time● Do not trust other fox hunters● If there are hills, always choose a

route on the top of a ridge. Careful with reflections in valleys

ARDF Competitions

● 28-30 May 2011 Shropshire ARDF FestivalLudlow, England, UK

● 5-10 September 2011 18th IARU Region I ARDF ChampionshipsOradea, Romania

● 16-18 September 2011 6th IARU Region II ARDF ChampionshipsAlbuquerque, New Mexico

● 23-28 September 2011 5th IARU Region III ARDF ChampionshipsVictoria, Australia

● September 2012 16th World ARDF ChampionshipsSerbia

● September 2014 17th World ARDF ChampionshipsAstana, Kazakhstan

ARDF Web Links

● http://en.wikipedia.org/wiki/Amateur_radio_direction_finding

● http://www.ardf-r2.org/

● http://www.homingin.com

● http://www.texasardf.org

● http://www.darc.de/referate/ardf/english.htm

● http://www.mydarc.de/df1fo/indexeng.html

● http://www.rac.ca/en/amateur-radio/operating-technical/ardf/

● http://www.pejla.se/ardf_games.htm

● http://www.kkn.net/mailman/listinfo/ardf