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FINAL ASSEMBLY
Our last task is to mount the antenna switcher cable to the ANTINT circuit
board. Special care must be used to ensure that the antennas sequence in
the correct order for proper operation of the RDF unit. You can use any type
of 5 conductor wire; 4 pair telephone wire or computer LAN cable works well.
If you look closely at the male DB9 connector provided with your kit you will
see that each of the pins is numbered. Solder one end of each of your 5
wires to the pins numbered 1 through 5. It is then a simple matter to follow
the wire to its opposite end and solder them to the ANTINT PC board. Pin 1
is soldered to ANT1, pin 2 to ANT4, pin 3 to ANT3 and pin 4 to ANT2. The
last wire is ground and solders to the ground point on the PC board. Once
assembly and test have been completed on the antenna switcher circuit
board you may affix a "jar cap" over the assembly to weatherproof. You can
place your iron on the plastic cap to make clearance reliefs to allow for cable
routing. The cap can be permanently installed using a hot melt glue gun or
other sealer of your choice.
INITIAL TESTING
Basic Testing
It is wise to review your workmanship, looking for circuit shorts or opens prior
to applying power. Use an ohmmeter to measure the resistance between
power and ground; the value should be greater than 2k ohms. Apply 12
VDC to the RDF unit with the power supply current limited to 150mA to pre-
vent damage in the event of a problem (normal current drain is 100mA). Ver-
ify the presence of the following supply voltages: = 5V on the output of VR1,
pin 16 of U8, pin 8 of U4, pin 8 of U6, pin 16 of U7, pin 24 of U11, pin 16 of
U5. Verify +2.5 V on pin 14 of U3, verify +12 V on pin 4 of U1 and U2. This
completes the basic testing of the Doppler RDF circuit. The following tests
are recommended to identify and trou-
bleshoot problems, but don't worry if
you don't have all the necessary test
equipment. Satisfactory performance
can usually be achieved without per-
forming these tests.
Functional testing
Before connecting the antenna switcher,
verify the operation of clock oscillator U4
by connecting an oscilloscope to pin 3.
The output should be a square wave with
an amplitude of 5 V and a period of 125
DDF1 • 27
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