Feature Articles
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An introduction to Radio Direction Finding, particularly for MSARS members.
Below are the instructions for a typical MSARS RDF event (Please Note may well vary from Hunt to Hunt.)
As usual the start time from Cyprus Road car park will be at 7.30pm. First transmission from the Fox will be at 7.30pm. Thereafter each transmission will be every 15 minutes, i.e. 7.45, 8pm, 8.15pm, 8.30pm etc. Each transmission will be for a duration of 2 minutes.
Arrive at the car park in plenty of time to allow you to set up and be ready for the first transmission.
At the start you will have been given a sealed envelope which contains the name of the pub near to where the foxes lair is. On no account should the envelope be opened, unless you have been unable to find the fox and given up. In this case open the envelope, and you will find details of the name of the pub and where it is located.
For the hounds that have found the foxes lair, please hand in your sealed envelope to Mr Fox.
The transmissions will be on a frequency of 145.400MHz. If this frequency is in use, you will be given an alternative frequency.
Map, Compass, Ruler and pencil are useful when taking various bearings of Mr Fox’s transmissions. In most cases Ordnance Survey Map 198 will suffice.
Clues will be transmitted by the Fox at 8.45pm, 9pm, and 9.15pm.
You will of course, need a device that will receive the transmissions. This could be a portable VHF receiver or transceiver. The antenna could be a simple whip using your body to act as a reflector/shield. Alternatively, a more sophisticated directional antenna such as a HB9CV antenna could be employed.
Many different types of antenna have been used over the years, and some of the most primitive of antenna have helped in successfully finding the Fox.
As you get closer to the Fox the signal from him will generally get stronger, and direction finding might become a problem as his signal will be reflected off buildings and the like. This is where an Attenuator is very useful. A few of the club members have made these in the past. This would make a good club project for the new members.
Each car and its occupants will be treated as one hound. A friend is welcome to accompany a member providing they travel in the same vehicle.
Please note that the actual start time of an RDF event, the duration of transmissions and the chosen frequency from the Fox may vary.
Full details of any particular hunt should be shown on the events page of this website.
Enjoy - Its great fun!
Tony G3XQM
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HF Propagation Predictions - February 2016
Courtesy Chris G3YTU
Download as a .pdf file
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Reduction of RFI for the Mobile User
Courtesy Phil M5BTB
Download as a .pdf file
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Decibel to Power Conversion Chart for the Radio Amateur
| dBW | Watts | Watts | dBW | |
| 0 | 1.0 | |||
| 1 | 1.3 | 1 | 0.0 | |
| 2 | 1.6 | 2 | 3.0 | |
| 3 | 2.0 | 3 | 4.8 | |
| 4 | 2.5 | 4 | 6.0 | |
| 5 | 3.2 | 5 | 7.0 | |
| 6 | 4.0 | 10 | 10.0 | |
| 7 | 5.0 | 15 | 11.8 | |
| 8 | 6.3 | 20 | 13.0 | |
| 9 | 7.9 | 30 | 14.8 | |
| 10 | 10.0 | 40 | 16 | |
| 11 | 12.6 | 50 | 17.0 | |
| 12 | 15.8 | 60 | 17.8 | |
| 13 | 20 | 70 | 18.5 | |
| 14 | 25.1 | 80 | 19.0 | |
| 15 | 31.6 | 90 | 19.5 | |
| 16 | 39.8 | 100 | 20.0 | |
| 17 | 50.1 | 120 | 20.8 | |
| 18 | 63.1 | 140 | 21.5 | |
| 19 | 79.4 | 160 | 22.0 | |
| 20 | 100 | 180 | 22.6 | |
| 21 | 125.9 | 200 | 23.0 | |
| 22 | 158.5 | 240 | 23.8 | |
| 23 | 199.5 | 280 | 24.5 | |
| 24 | 251.2 | 320 | 25.1 | |
| 25 | 316.2 | 360 | 25.6 | |
| 26 | 398.1 | 400 | 26.0 |
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The Phonetic Alphabet
The NATO Phonetic Alphabet was developed in the 1950s to avoid the misunderstanding caused by poor radio acoustics where an S and an F for example are easily confused.
A - Alpha
B - Bravo
C - Charlie
D - Delta
E - Echo
F - Foxtrot
G - Golf
H - Hotel
I - India
J - Juliett
K - Kilo
L - Lima
M - Mike
N - November
O - Oscar
P - Papa
Q - Quebec
R - Romeo
S - Sierra
T - Tango
U - Uniform
V - Victor
W - Whiskey
X - X-ray
Y - Yankee
Z - Zulu
