Getting Started in ARDF
Your First Practice Event
de Dale Hunt WB6BYU
Your first practice event may have many people looking for five
transmitters, or maybe your friend hid a transmitter down the street
from your house. We will go through the hunt with you so you know
what to do, and what to expect.
Let's begin with a simple hunt - only one transmitter. First, you need
to know the frequency the transmitter is on, so you can tune your receiver
to hear the signal. When you can hear it, take a bearing. Since there
is only one transmitter, we will just go in the direction of the bearing
until we reach it. We must always be aware of where we are, and where we
are going. It is not uncommon for someone to find a transmitter without
knowing where they actually are if they were not paying attention!
If we are in an open area, we can just start walking in the proper
direction. But often that is not possible. The next best choice is to
take the trail or road that runs closest to the desired direction. As
you walk along, the bearing to the transmitter will change. Also, as
you get closer to the transmitter, the signal will get stronger, and
you may have to turn down the gain control on the receiver. If you come
to another path that runs closer to the current transmitter direction,
you may want to take that path. Of course, it will depend on how many
paths there are and where they go relative to the where the transmitter
is hidden. But keep taking bearings on the transmitter and going as
near as possible to that direction.
There are two warning signs that you are close to a transmitter: the
signal will be very strong and the bearing to the transmitter will
change quickly as you walk along. If you are walking down a straight
road and the transmitter is hidden just to the side of it, the initial
bearing might point exactly along the direction of the road. If the
transmitter is 500 meters away, and 50 meters to one side, the initial
bearing will be only 6 degrees different from the direction of the
road - not enough to notice. After walking 400 meters, the bearing
will change by about 20 degrees. Another 50 meters down the road,
and the bearing to the transmitter will be 45 degrees from the road,
and it will change to 90 degrees in the next 50 meters. If the
transmitter is closer to the path, the change in bearing will be even
more sudden. (You can estimate how far the transmitter is off the road
by measuring the distance between the point where the bearing is 45
degrees from the direction of the road and where it is 90 degrees from
the road - this is the same distance that the transmitter is from the
If it is difficult to walk off the road, then the best approach is
usually to follow the road until the bearing is 90 degrees from it,
then follow the bearing to the transmitter. But maybe there is a large
lake in the way! Then you need to decide whether the transmitter is
on this side of it or on the other side. If the signal is very strong,
and the bearing moves quickly as you walk down the road, then the
transmitter may be on your side. But if the signal is not as strong,
and the bearing did not change as quickly, the transmitter is probably
on the other side. As you get more practice, you will learn how to
interpret what the receiver is telling you to make these decisions.
If the transmitter is on the other side of the lake, find a path that
takes you there and continue hunting.
Although you may have to make detours around objects you can not walk
through, this method of following the bearing to the transmitter is
simple, and will usually get you to thetransmitter. But sometimes
the hunts are more difficult, with more than one transmitter.
A standard ARDF course has five transmitters, and choosing the best
order in which to find them is an important part of the competition.
In this case, you will generally have a topographic map of the area
where the transmitters are hidden. Though the transmitter locations
will not be marked on the map, the map will indicate roads, trails,
elevations, and physical features such as forest, clearings, and lakes.
The map should also indicate magnetic north, and there will be
straight lines of magnetic north bearings at a regular interval across
the map. An ARDF competition map will mark the locations of the start
and the finish.
Now you are trying to keep track of all the transmitters as they transmit
in turn. Especially in your first practice event, it is best to focus
on actually finding the transmitters instead of trying to be fast. Once
you learn the basic skills, you will be able to do it faster without making
many mistakes. So, for this hunt, after you start, find a convenient
place that you can accurately locate on the map to stop and take bearings.
Some examples of locations that are easy to accurately locate on a map are
where two trails or roads meet, where a trail enters a large clearing, the
top of a well-defined hill, or where any distinctive feature such as a pit,
a lone tree, or cultural artifact (i.e. an abandoned car) are marked on
the map. Bearings taken while crossing large sections of terrain without
distinctive features are still helpful, but it is harder to know where
exactly you are on the map. Each transmitter is on for one minute at a
time, and for beginners it may be difficult to take an accurate bearing
and plot it on the map in that time. Don't worry about being very
accurate at first - just write down the bearings you get for each
transmitter, and then plot them on your map.
There are two common ways to plot a bearing. You can mount a compass
to your antenna or receiver. Make sure there are no steel parts that
deflect the compass needle. Mount the compass so that 0 degrees is in
the direction of maximum antenna sensitivity. If you reverse the
numbering around the compass dial (so that the numbers become
progressively larger in a counter-clockwise direction rather than in a
clockwise direction,) you can just read the number that the red end of
the compass needle points to, and that is the direction the antenna is
pointing. (A compass with this kind of marking is said to have a reverse
bezel.) Using a protractor, draw a line in this direction on the map,
starting from the point where you are standing. After you have plotted
several bearings for each transmitter from several different locations,
your map will be very messy, so it helps to use a different color marker
for the lines to each transmitter.
Another approach is to orient the map to north using your compass, then
lay the receiver on it while taking a bearing. Draw a line in the
direction the receiver is pointing, starting from your current location
on the map. With practice, you will find the method that works best
Now we have initial bearings on all of the transmitters. This does not
tell us where they are, but it gives us good information. The other
thing we want to check is the signal strengths: a weak signal usually
means the transmitter is further away. A strong signal means the
transmitter is closer: if one signal is much stronger than the others,
we may want to go to that one first because it is the closest.
Unless one transmitter is obviously closest, a good strategy is to start
with the one that appears to be the furthest from the finish. (If the
start and finish are at the same place, then start with the transmitter
furthest at one end of the group.) As you go along, you will get more
information about the exact transmitter locations, but you have enough
information to get started.
Once you have chosen the first transmitter, hunt it as discussed above.
Follow convenient paths such as roads or trails to get as close as
possible to it before walking through the forest to find it. Because the
transmitter is on for one minute and off for four minutes, it is possible
to walk past it when it is not transmitting. When the signal is very
strong in your receiver, watch carefully for the orange and white
transmitter control flag. But do not spend too much time looking; if
you do walk past it, you will find out the next time the transmitter
comes on, and you can go back and find it. Each time the transmitter
comes on, check the bearing to the transmitter. Correct your direction
of travel if necessary. Towards the end of the one minute transmission,
make a mental note of the current compass bearing. Then you can continue
following the compass in the same direction until it comes on again.
With practice, you will also be able to judge how close you are to
the transmitter by the signal strength: this is very useful, because
if the distance is further than you can run or walk in four minutes,
you do not have to worry about looking for the transmitter this time while
it is off.
Meanwhile, take bearings on the other transmitters while you are walking
towards your first one. Once you have gone 500 meters or more, you can
plot another set of bearings on your map and see where the bearing lines
cross for each transmitter. Of course, no bearing is perfect, but when
you have three bearing lines for a transmitter that go to the same
general area, you can go there and you will probably be fairly close when
the transmitter comes on.
Each transmitter should have an orange and white control flag located
75 to 100 centimeters off the ground and in a location where you can see
it when you get within about ten meters of the transmitter. In competition,
it will have some type of marker so you can show you actually found the
transmitter. This might be an electronic device into which you push a small
memory stick you carry with you (usually attached to a finger with elastic,)
a punch that makes a special pattern of holes in a paper card you carry
with you (perhaps stapled to your map or pinned to your shirt,) or a
particular color of pencil that you use to mark a paper card you carry
with you. In your excitement that you found the transmitter, make sure
you remember to "punch in!"
By the time you find the first transmitter, you should have a general
idea about where the other transmitters are located. You should probably
also have decided the order in which you should find them. Plan
the fastest route to the next one you want to find, using paths and
roads where available, and trying to avoid steep hills or heavy brush
that is difficult to walk through. As you hunt for the other transmitters,
you will not need to plot bearings as often - just check that each bearing
from your current location is consistent with where you think the
transmitter is located each time it comes on.
Make sure you remember which transmitter you are looking for at all times!
Otherwise you may find the same transmitter more than once, which may be
good practice, but it is not the purpose of the competition. Also, try
to keep track of where you are on the map as you travel. It does not
help to plot a bearing on the map if you do not know where you are when you
take the bearing.
Most competitions will have a time limit. Especially on your first
practice, you may not have enough time to find all the transmitters.
You may want to skip the ones that are the furthest away, or are the
hardest to get to. Even if you only find one or two transmitters,
that is a good start, and you will learn a lot that will help you do
better next time.
After you find the last transmitter (or the last transmitter that you
have time to find,) go to the finish area. In competition, there will
be a beacon transmitter at the finish, transmitting on a different frequency
than the hidden transmitters. You can tune your receiver to the finish
beacon frequency and follow the bearings back. Alternatively, you can
rely on your map skills to get you from where you are to the finish
(which, unlike the hidden transmitters, is marked on the map.)
When you finish, think back over the hunt to see what lessons you can
learn. Look at your bearings and see how close they were to the actual
locations where you found the transmitter - if the errors tend to be
mostly in one direction, maybe your compass is not properly aligned or
is being affected by the receiver, or maybe you are not plotting the
bearings properly. Perhaps you can discuss the hunt with a more experienced
competitor who has just run the same course and find out what decisions
they made. The best competitors always learn from their mistakes.
One problem you will find, especially when on hunting on two meters, is
signal reflections and blockages. With a VHF signal, if there is a hill
between you and the transmitter, it will block the signal path. The
transmitter behind the hill may have a very weak signal, or you may
instead pick up a stronger signal from the transmitter that is being
reflected from another hill. If you have this problem, the best solution
is to move and take a bearing somewhere else. Look for a hill or other
high place with a clear view in the transmitter direction. Also, if you
have conflicting bearings, usually those taken on the strongest signals
will be the most reliable.
Reflections are rarely a problem when hunting on eighty meters. Bearings
are usually clear and accurate, although if you are standing near
telephone or power wires, a long fence, railroad tracks, or inside a
building, the bearings may not be as accurate.