DDF1 • 30
Scan/stop switch S2 stops the antenna from spinning. Close and open S2
until the voltage on terminal J2 pin 1 reads +5V. Pins 2, 3 and 4 should all
read 0V. Pin 1 is the antenna enable signal for antenna 1. Label the corre-
sponding mag mount antenna on the table as antenna 1. Close and open S2
until the voltage on terminal J2 pin 2 reads +5V. Pins 1,3, and 4 should all
read 0V. Pin 2 is the antenna enable signal for antenna 4 and should be po-
sitioned to the right of antenna 1 as viewed from the center of the antennas
for a clockwise spin. Close and open S2 until the voltage on terminal J2 pin
3 reads +5V. Pins 1,2, and 4 should all read 0V. Pin 3 is the antenna enable
signal for antenna 3 and should be positioned to the right of antenna 2 as
viewed from the center of the antennas. Close and open S2 until the voltage
on terminal J2 pin 4 reads +5V. Pins 1, 2, and 3 should all read 0V. Pin 4 is
the antenna enable signal for antenna 2 and should be positioned to the right
of antenna 3 as viewed from the center of the antennas.
Testing the RF operation of the antenna is quite simple. Place all four mag
mount antennas around the center of the car roof, placing each antenna at
the corner of an 18.25 inch square pattern for operation on 146 MHz. Do not
install any of the whip antennas yet. Connect the RF output of the antenna
switcher to an FM receiver or transceiver tuned to a strong NOAA weather
broadcast signal. Caution: Make sure you disable transmit mode if you
are using a transceiver!
Apply power to the RDF unit and open S2 to stop the spinning process.
Take one whip antenna and touch it to the mounting screw on each of the
mag mount antennas. Only one antenna should provide a signal strength
reading similar to it being connected directly to the FM receiver. Remove the
whip from the selected antenna and touch it to each of the other three anten-
nas. The NOAA signal should be weak or nonexistent. Close and open S2
until another antenna is selected and repeat the same test. Continue the
process until you have verified each antenna can be turned on while the
other three remain off.
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
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