Instruction manual
DDF1 34
Operation
Checking performance of the RDF unit is best done in a large, empty area
away from tall buildings: a parking lot will do. Use caution at all times during
open road operation of the RDF unit. Use a minimum of two people for all
testing and operation of the RDF unit: one to operate the vehicle and the
other to operate the RDF unit. The magnets securing your antennas to the
roof of the car were designed for use at reduced speeds. If you intend to use
the DDF1 at highway speeds, you may want to get some stronger magnets.
The powerful magnets contained in computer hard drives are excellent for
this application and can often be found at flea markets or surplus store for as
little as $1.00 or less. The typical magnet found in an audio speaker would
also work well. As a safety measure, secure each mag-mount antenna with
20 pound fishing line when operating the vehicle at highway speeds.
Attach all four whip antennas to the mag-mount antenna bases placed about
the center of the car top. Connect the RF output of the antenna switcher to a
FM receiver transceiver tuned to the desired frequency.
CAUTION:
Make sure you disable transmit mode if you are using a transceiver!
It is best to use a smaller, handheld walkie talkie with your DDF1. The unit
connects easily to the antenna on your handheld and because they have
less output power, there is less chance of doing damage by accidentally
transmitting into your DDF1.
Adjust the receiver's audio to a comfortable level in the external speaker.
Apply 12 V to the RDF unit and “spin” the antenna by closing switch S2. As
soon as S2 is closed, you should hear a 500 Hz tone imposed on the re-
ceiver audio. Rotate audio level adjust control R50 so that low signal level
LED D4 and audio overload LED D3 are extinguished. Never trust direc-
tional indications if D3 and/or D4 are illuminated. The direction indicating
display should be relatively constant with a single LED lit, or one or two adja-
cent LEDs alternately illuminating. Adjust calibrate control R36 so that the
direction indicating LED is consistent with the general direction of the trans-
mitter with respect to your location and the position of the car. Have the
driver slowly circle while you observe the display. You should see the direc-
tion indicating LEDS illuminate in the opposite direction as the car is turning
in a circle. The position changes relative to the changing direction of the car,
however, the direction indicated from the center of the circle the car is driving
should remain fixed. If the display turns in the same direction as the car, flip
phase invert switch S3 to the opposite position to correct the 180 degrees
phasing offset. This completes the rough calibration procedure.