In the beginning
I started ARDF in 2009 so my experience is rather limited. It seemed a natural progression being a radio ham and also being interested in running. My original equipment was borrowed at the time of the event (as is usual for most folk starting off). Quite quickly I bought some kit based equipment.
My 80m receiver was bought from the father of UK ARDF, Bob Titterington G3ORY. This still forms the basis of what I use today.
Its great fun and keeps you fit and active at the same time, the competetive spirit is there for those who want it but most just enjoy the day out and the thrill of finding the hidden fox.
What is ARDF?
If you're reading this you probably know. Amateur Radio Direction Finding is the sport of using receiving equipment to locate hidden transmitters. There are a few variants but typically five hidden transmitters (foxes) are hunted by competitors in a rural / forested location. Orienteering style maps are used to navigate the area and total run distance maybe 5 to 12 km. Of course running isn't compulsary but it is usually faster. Each transmitter is active for 1 minute in every 5 minutes which hinders the location process. The competitor will swing the antenna full circle to estimate the beam heading of the hunted transmitter.
There are two separate frequency bands used, 144MHz (2m) and 3.5MHz (80m), each band has their own characteristics of
introducing errors and difficulties during hunting. Generally 3.5MHz gives a more accurate and consistent beam heading whereas 144MHz is more prone to reflections from landscape features.
My 2m equipment was sourced from David Deane G3ZOI. A superb ROX2T and tape measure yagi.
Improvement and experimentation
After several events the interest in ARDF was such that I wanted to explore new ideas to improve my performance.
My fitness is perhaps my strongest attribute but I felt severely let down by poor navigational skills. Many competitors have been introduced to ARDF from an interest in orienteering, map reading is therefore second nature. I often found myself getting lost and wasting time trying to work out my position. Also my ability to keep running along a fixed beam heading wasn't too good and indeed many other aspects such as distance estimation and route decisions needed impovement. Obviously more experience will help as well as specific training in orienteering events which I have subsequently taken part in. However from a technical point of view there must be significant improvements that can be made to the relatively simple equipment I was using.
I compiled a list in my own mind of the improvements that could be made to squeeze a few more minutes off my time. A summary of the points are given below and expanded upon later.
1. To assist in the determination of the position of the fox using electronic triangulation.
Theoretically it's not difficult to understand that if the competitor has generated a number of beam headings from various positions on the course then the meeting point of those beam headings will approximate to the postion of the fox. Indeed, that is what most competitors do in a real race, to draw beam headings on the map and see where they meet. For me, the errors in this process amounted to the position being far from reality. Can this be improved?
2. To improve upon the functionality of the radio.
Not ground breaking, but I wanted a radio that was sensitive, didn't drift and offered other functions such as a wide dynamic range audible signal strength indication.
3. To utilise the time we have more effectively, somehow derive a method of competing to be able to calculate fox position while still being able to maintain a high average speed.
i) Generally we are not running anywhere near optimum speed while taking bearings.
ii) The bearings we do take maybe subject to error depending upon the exact location the bearing was taken.
iii) In one minute of transmission there is a compromise to be made, do we run or stop to take readings.
iv) Due to the eagerness to run are the bearings we take too few and too inaccurate to make a good estimate of position?
The present technique of swinging an antenna around seems so wasteful, the idea of running whilst continually (and automatically) collating and processing information is very appealing to me. I'd like to analyse the effectiveness of Angle of Arrival estimation using multi-antenna phase difference techniques.
To see how I'm progressing click the icon.