4. WHIP ANTENNA ADJUSTMENT
The direction pattern of whip and ferrite antenna combined asks for exact ratio between voltages
from each antenna. While the voltage from ferrite antenna does not depend to the height above
ground, the voltage from whip antenna depends on it. Therefore you can get optimum direction
pattern only within about 50 cm tolerance of the given height above ground.
Of course, the maximum/minimum can be easily recognized in any height above ground. However, if
you trim your antenna according to your personal height, you will reach excellent front-to-rear ratio
(some 40 dB!).
Trimming procedure:
Install the ARDF transmitter, set it to continuous operation at the center of the 3,5 MHz band.
Stay some 70 m away from the transmitter, away from fences, electric wires, etc.
Tune the receiver, push and hold the antenna button and aim the receiver front panel towards
the transmitter (minimum of the "cardioid" antenna pattern).
Move the receiver up and down. You should see a minimum of the signal at certain height
above ground.
If the minimum is at the level you normally hold the receiver, everything is OK. If the minimum
appears lower than you want, you shall shorten the whip (this is probably your situation). If the
minimum appears higher than wanted, you shall lenghten the whip.
Trim the whip by short pieces (5 mm) until the minimum moves to the wanted height above
ground.
Note: in close vicinity of the transmitter (<10 m) the ratio mentioned above changes again
(magnetic and electric components of the RF field increase differently close to the antenna) -
very close of the transmitter the whip appears as it should be even shorter. Nevertheless, from
such short distance you usually can see a flag and it is better to have an optimum direction
pattern through the rest (>95%) of the competition.
5. INCREASING WATERPROOFNESS
The back cover of the receiver is sealed with a silicone glue inside. If you open the receiver (for
exchanging the battery or drying the receiver), please remember to seal it again (at least with Scotch
tape from outside) after closing the cover back.
6. ELECTRONIC COMPASS MODULE OPERATION (optional)
The FINDER09 allows the competitor to keep stored direction exactly even after the end of the
transmission period.
The FINDER09 is controlled by the blue button on the right side of the receiver. When you short click
the button, the current direction is stored into memory and this is indicated by a short trill in your
headphonest. When you push and hold the button, you activate tracing mode and according to the
current direction you will hear a tone in your headphones (in addition to the normal received signals
from the band).
If the receiver is aimed to the stored direction or up to 20° to the left, you will hear low pitch in your
headphones (833 Hz), if the receiver is aimed up to 20° to the right from the stored direction, you will
hear high pitch (1250 Hz). At the exact direction the pitch just changes. Out of the +-20° range no
tone can be heard in the headphones.
The direction remains stored in the memory until you store another one by clicking the button (even if
you release the button). If you turn off the receiver, the memory content is lost.
Using the compass: Let us assume that you are running towards the transmitter. Before the end of
transmitting period aim the receiver to the desired direction and click the compass button. After the
end of transmitting period, you simply continue to run in full speed and from time to time check the
SF35M_inf_en Rev. 17W04 | Page 2 of 4 (c) OK2BWN
