Main Board Functional Test (continued):
Step 104: Depress and hold the CALIBRATE pushbutton switch while
turning
on the power switch. Hold the CALIBRATE switch down for about 2 seconds after
power is applied. You should see all of the RED LEDs flash twice, followed by a
clockwise circle of the LEDs then a counter clockwise circle. The display should
continue to flash all LEDs at the end of this sequence. Closing the CALIBRATE
switch during power on causes default data to be written to the EEPROM. This
should only be necessary the first time the unit is powered up. All stored
calibration data will be erased. Note: the default values may give readings that are
far from correct. This is not an issue, you will correct the readings during the
following steps.
Step 105: If any LEDs fail to light or light out of sequence verify that they
are connected with the red lead to the round pad and white lead to the square pad.
If they circle counter clockwise first, followed by a clockwise circle then the LED's
were wired to the board in the reverse sequence.
Step 106: Carefully connect a jumper from test point TP1 to test point TP0.
One LED should light And you should hear an 800 Hz tone in from the speaker,
Don't worry about which light lights, you will adjust that in the next step.
Step 107: With the jumper still connected, depress the CALIBRATE
pushbutton and hold it for about 3 seconds. The LED's will all flash twice and then
go out.
Step 108: Release the CALIBRATE push button. The 0 degree LED should
now be on. If a different LED is on instead then repeat steps 99 through 102 . If the
wrong LED is still on then check your LED connections on the board for wiring
errors.
Step 109: Remove the jumper from TP-0, the 0 degree LED should flash
indicating a loss of signal and that 0 degrees was the last relative bearing.
Step 110: Carefully move the jumper to TP-90. The 90 degree LED should
light.
41
Main Board Functional Test (continued):
Step 111: Remove the jumper, the 90 degree LED should begin flashing.
Step 112: Carefully move the jumper to TP-180. The 180 degree LED should
light.
Step 113: Remove the jumper, the 180 degree LED should begin flashing.
Step 114: Finally move the jumper to TP-270 The 270 degree LED should
light.
Step 115: Remove the jumper, the 270 degree LED should begin flashing.
700Hz Antenna Speed Testing:
Step 116: Turn off the power switch.
Step 117: Depress and hold S104, (the SPEED pushbutton) while turning on
the power switch. Release S104 and connect the test jumper to TP-0 You should
now hear a 700Hz tone form the speaker. If in doubt, leave the jumper on J103
and cycle the power switch. You should hear the tone change to a higher pitch,
(800 Hz).
Step 118: Turn off the power and remove the jumper. The Main Board
Assembly and Testing is complete.
Step 119: Mount the circuit board in its enclosure using four #4-40 machine
screws and brass #4 x ¼" spacers between the solder side of the board and the
enclosure.
42
RS-232 Interface Test:
The RS-232 interface accepts NMEA GPS "$GPRMC" data from the GPS, uses it
to calculate magnetic bearings from the DSP Doppler's Relative bearings and then
provides the computer with both GPS and Doppler bearing data to the computer.
Other NMEA data sentences are ignored by the DSP Doppler and are simply
passed on to the computer
The Doppler divides 360 degrees into one hundred 3.6 degree buckets.
Bearings are truncated to integer values with a suffix of ".0" added . For example a
bearing of 136.8 is reported as 136.0 degrees.and 36 degrees is reported as 36.0
degrees. NMEA GPS data always starts with the characters $GP or "$PR" followed
by the type of data and ends with an asterisk and two hexadecimal digits.
Typical $GPRMC NMEA data sentence would look like:
$GPRMC,005400.722,A,3348.2416,N,11756.5894,W,0.00,218.29,290604,,*17
This particular NMEA sentence contains all the information the Doppler needs to
provide magnetic bearings as well as the position and speed information needed by
software packages. Other NMEA sentences contain other types of data which
generally is of no use to us in this application.
Doppler output data is provided to the RS-232 computer port in one of two
formats, the format used depends upon the presence of valid GPS data.
The first Doppler format consists of a percent sign followed by a 3 digit heading, a
decimal point, and "0/" and a single digit representing the signal quality from 0,
(poor) to 9, (excellent )
The second Doppler format is identical to the first except that it adds another "/"
followed by a 3 digit integer magnetic bearing value ranging from 000 to 359
degrees, a decimal point and a 0.
43
RS-232 Interface Test (continued):
An example of the first format, we'll arbitrarily call it Doppler output format 1, is:
%136.0/9
This represents a relative bearing of 136 degrees with a quality of 9 (excellent).
An example of Doppler format 2 is:
%136.0/8/158.0
in this example the relative bearing is 136.0 degrees, the signal quality is 8 and the
magnetic bearing is 158.0 degrees. To generate this magnetic bearing the Doppler
would have received a valid GPS heading of 22 degrees, ( 136 degrees + 22
degrees).
Step 120: Connect a DB9 Male to DB9 Female extension cable between the
computer and the DSP-Doppler Main unit.
Step 121: Start a terminal emulator program, such as hyperterminal or
TeraTerm, ( http://hp.vector.co.jp/authors/VA002416/teraterm.html )
on the computer. TeraTerm is a very useful free emulator because it is very user
friendly, and allows logging and replay of both binary and ASCII data.
Step 122: Set the terminal emulator to 4800 baud, 8 bits, no parity and no
flow control.
Step 123: (Optional but Recommended) If you can also specify a log file, it
might make it easier to confirm the proper operation of the RS-232 interface.
Step 124: Connect a jumper between TP1 and TP0 on the main board.
Step 125: Turn on the power to the DSP DOPPLER . You should see a string
of data that looks like
%000/9.
The reading may be +/- about 4 degrees. If it is far outside this reading then press
and hold the CALIBRATE button for 3 seconds until the display flashes twice then
release the button.
44
RS-232 Interface Test (continued):
Step 126: Connect the GPS to P101 on the main unit and turn on the GPS
power. Make sure the GPS has fresh batteries and is in a location where it has
a good view of the sky.
Step 127: You should see GPS data streaming across the screen interspersed
with %000/9 this represents "True Bearing" / "Quality " Watch the GPS data, one
line will look something like :
$GPRMC,005400.722,A,3348.2416,N,11756.5894,W,0.00,218.29,290604,,*17
Each field is separated by a comma, the third field will contain either "V" or "A",
"V" means that the data is not valid while "A" indicates valid data, this is the GPS
Data Quality Flag. Most GPS units will start out displaying a "V" for a few
minutes until the GPS acquires enough satellites to navigate.
After the GPS data quality flag changes to "A" the DOPPLER data output line
should change to format 2, looking like %000.0/9/nnn.0 the "nnn.0" portion is the
magnetic Bearing represent by the relative bearing corrected for the GPS heading.
This can be any value from "000.0" to "359.0" depending on the GPS heading and
the relative bearing.
It is important to note that if the GPS data validity flag fails to change to "A" this is
not a function of the Doppler but rather an indication that the GPS needs to be
relocated to a location where it has a better view of the sky. Low batteries in a GPS
could also cause this problem.
If you wish to actually see the corrected bearing you will have to take the unit for a
ride in your car while repeating the GPS tests.
You can use live DF data for this test instead of the jumper between TP1 and TP0,
simply leave the jumper off and connect the main unit to the antenna switch and
antennas and tune in a signal while driving.
45
Assembling the Antenna Control Board
FIGURE 5 ASSEMBLING THE ANTENNA CONTROL BOARD
Inductor Selection
Two values of inductors are supplied with your kit. You must choose the proper
one here. All inductors on the Antenna Control board and all four of the Antenna
Interface boards must be of the same value.
.22 uH used for the 70 cm, (440 MHz ) band.
.47 uH used for the 2 Meter ( 144 MHz) band.
Reference figure 6. Mount the DB9 male connector on the component side
of the Antenna Control board.
Step 128: Mount pin diode D4, (MPN3700). Align with the flat side as
shown in figure 6. The diode should be 1/16" to 1/8" above the circuit board for
ease of flux removal.
Step 129: Mount resistor R3, (220 Ohm).
46
Assembling the Antenna Control Board (Continued)
Step 130: Mount capacitor C14, ( 1nF) .
Step 131: Mount capacitor C5, ( 1nF).
Step 132: Mount inductor L3. Reference the note under figure 5 for
determination of the proper value. All inductors on this board must be the same
value.
Step 133: Mount capacitor C4, (470 pF).
FIGURE 6 ASSEMBLING THE ANTENNA CONTROL BOARD
47
Assembling the Antenna Control Board (continued)
Reference figure 6.
Step 134: Mount pin diode D6, (MPN3700). Align with the flat side as
shown in figure 6. The diode should be 1/16" to 1/8" above the circuit board for
ease of flux removal.
Step 135: Mount resistor R5, (220 Ohm).
Step 136: Mount capacitor C15, ( 1nF) .
Step 137: Mount capacitor C8, ( 1nF).
Step 138: Mount inductor L5. Reference the note under figure 5 for
determination of the proper value. All inductors on this board must be the same
value.
Step 139: Mount capacitor C7, (470 pF).
FIGURE 7 ASSEMBLING THE ANTENNA CONTROL BOARD
48
Assembling the Antenna Control Board (continued)
Reference figure 7 above.
Step 140: Mount pin diode D8, (MPN3700). Align with the flat side as
shown in figure 7. The diode should be 1/16" to 1/8" above the circuit board for
ease of flux removal.
Step 141: Mount capacitor C11, ( 1nF) .
Step 142: Mount resistor R7, (220 Ohm).
Step 143: Mount capacitor C16, ( 1nF).
Step 144: Mount inductor L7. Reference the note under figure 5 for
determination of the proper value. All inductors on this board must be the same
value.
Step 145: Mount capacitor C10, (470 pF).
49
Assembling the Antenna Control Board (continued)
FIGURE 8 ASSEMBLING THE ANTENNA CONTROL BOARD
50
Assembling the Antenna Control Board (continued)
Reference figure 8.
Step 146: Mount pin diode D2, (MPN3700). Align with the flat side as
shown in figure 8. The diode should be 1/16" to 1/8" above the circuit board for
ease of flux removal.
Step 147: Mount resistor R1, (220 Ohm).
Step 148: Mount capacitor C2, ( 1nF) .
Step 149: Mount capacitor C13, ( 1nF).
Step 150: Mount inductor L1. Reference the note under figure 5 for
determination of the proper value. All inductors on this board must be the same
value.
Step 151: Mount capacitor C1, (470 pF).
51
Assembling the Antenna Interface Boards :
FIGURE 9 ASSEMBLING THE ANTENNA INTERFACE BOARDS
Assembling the Antenna Interface Boards (continued)
NOTE: THE NYLON NUT IS NO LONGER NEEDED ON CURRENT BOARDS
Since all 4 Antenna Interface boards are identical you may wish to install the Same
component on each board before moving on to another component.
You must use the same value for the inductors, on each of the four antenna
interface boards as you used on the Antenna Control Board.
To change the configuration from 2 meters to 440MHz or vice versa it is necessary
to change all the inductors to the appropriate value.
Inductor value .22 uH used for the 70 cm, (440 MHz ) band.
Inductor value .47 uH used for the 2 Meter ( 144 MHz) band.
52
RS-232 Interface Test ( Continued):
Step
Board 1 Board 2 Board 3 Board 4 Operation
152
Position the board, component side
up as shown in figure 9.
153
Install Resistor R-ANT, 220 Ohm,
1/8 watt carbon film. Carefully
bend the leads to conform to the
hole pattern.
154
Install L-ANT. This component
value must match the value used
on the Antenna Control Board. For
2 Meter operation use the 4.7 uH
inductor. For 440 MHz operation
use the 2.2 uH inductor. In other
words you will use either all the
4.7 uH inductors or all the 2.2 uH
inductors but not some of each.
Install D-ANT pin, make certain
that it is Oriented as shown by the
silk screen on the board.
When soldering the pin diode,
solder as rapidly as possible and
make certain that it is positioned
about 1/16 inch off the board so
that you can see the solder fillet.
Excessive heat can damage this
component.
155
Install C-ANT 1 nF Capacitor,
carefully bend the leads to conform
to the hole pattern.
156
TABLE 2 ANTENNA INTERFACE BOARD ASSEMBLY
53
Assembling the Antenna Interface Boards (continued):
USE ONLY COTTON FOR THE
RAG IN THIS STEP,
SYNTHETIC FABRICS AND
WOOL MAY PRODUCE A
STATIC CHARGE AND
DAMAGE COMPONENTS.
This step should be performed in
a well ventilated area, away from
flames or cigarettes.
157
Wet A small stiff brush with clean
Isopropyl Alcohol, (Rubbing
Alcohol), remember it is
flammable! Briskly scrub each
solder joint on both sides of the
board to remove any flux. Blot off
the Alcohol from the board with a
cotton rag and then rinse the board
with a small amount of clean
alcohol. Blot dry on a cotton rag.
Install J-ANT, SO-239 connector.
This connector installs on the
solder side of the board using #440 machine screws and ¼ inch
spacers.
158
Use a metal spacer, nut and washer
fhrough each hole. Solder the
center pin to the board pad after all
screws are firmly tightened.
Table 2 (continued)
54
Assembling the Antenna Interface Boards (continued):
Repeat step 152, cleaning all flux
residue from the SO-239
connections
159
Table 2 (continued)
This completes the assembly of the Antenna Interface board set.
Antenna Orientation:
Regardless of the construction method the antennas should be arranged on a metal
ground plane in a square pattern on a circle of 20 inch to 29 inch diameter . (For 2
Meters). (26.87 inches diameter would give a ¼ wavelength spacing of 19 inches
between elements )
(All directions are relative to the vehicle, front left being the U.S. drivers side
front).
Antenna #1 must be the front left antenna,.
Antenna #2 must be the front right antenna.
Antenna #3 must be the right rear antenna.
Antenna #4 must be the left rear.
NEVER TRANSMIT THROUGH YOUR DOPPLER ANTENNA AS IT
WILL BE DAMAGED. I unplug the microphone from the radio I'm using
with the Doppler to help prevent this serious mistake.
Step 160: Mount the antenna unit on top of the vehicle. Make certain that no
other antennas are nearby. Nearby antennas can act as parasitic elements and cause
directional errors also they are more likely to be modulated by 800 Hz when
transmitting on another radio when the Doppler is running. If the Doppler
modulation causes an objectionable level of modulation in your transmissions then
it will be necessary to turn it off during your transmissions.
55
Calibration:
Calibration will be necessary any time you use your Doppler on a different vehicle.
In addition if you remove and replace the antennas on your vehicle and they do not
go back in precisely the same locations and geometry it will be necessary to
recalibrate.
Step 161: Connect the RF output from the Antenna Control unit to the FM
receiver’s antenna jack.
Step 162: Connect the Antenna Control cable between the Antenna Control
unit and the Doppler Main Circuit board.
Step 163: Connect the FM receiver's external speaker audio to the audio
input jack on the Doppler unit.
Step 164: Open the squelch on your receiver.
Step 165: Turn on the power to your Doppler unit.
Step 166: Turn on the receiver and tune it to the frequency desired. You
should hear a 700Hz or 800 Hz tone imposed on any audio present depending upon
the Antenna Speed selection at startup. (Pressing and holding the Ant Speed push
button at power up will select 700 Hz.)
The easiest way for most of us to calibrate is to drive to an open area and have a
friend position himself/herself at least 100 feet away and directly ahead of the
vehicle while transmitting an unmodulated carrier. If your buddy is using an HT
have him hold it vertical at approximately the height of the vehicle antennas. With
the Doppler already turned on, depress and hold the CALIBRATE pushbutton for
several seconds then release it. The 0° LED should indicate that the signal is
directly ahead of the vehicle. As a double check your buddy can then transmit
while circling the vehicle at approximately the same distance and the display
should follow him/her.
That is all that is needed. The Doppler will retain this calibration even after power
is turned off as long as the antennas aren't re-positioned.
56
An alternate method of calibrating the unit is to perform the calibration while
driving across an open area directly towards a known transmitter site. This will
give you the best calibration but may be difficult or impossible in urban areas. The
simpler method should be quite adequate.
Some Foxhunting Tips:
For safety, you should always have at least two persons in the vehicle while
Foxhunting/DF’ing. One person should concentrate on the driving and the other(s)
on display interpretation and map reading.
One effective search methodology is to drive in the general direction of the RF
source until display changes to 90° or 270° . At that time turn towards the source
on the nearest street and continue until the display again reads 90° or 270° . At that
time repeat the sequence.
Should you loose the signal, continue on the course until you re-acquire it. Do not
be too hasty to go some other direction.
You may develop other methodologies that work better in your situation and by all
means use them.
57
Addendum:
Circuit Board Layouts:
DSP-001 Version 2.0 Main Circuit Board Layout
FIGURE 10 DSP-001 VERSION 2.0 MAIN BOARD LAYOUT
The two empty sockets are for the Microprocessors, U101, (in the center) and
U103 near the bottom. Note: there is no crystal or associated capacitors installed
for U101 this the case only if the U101 Microprocessor is an Atmel AT90S1200.
The planned replacement for the AT90S1200 in the future will require a crystal.
58
DSP-002 Antenna Control Circuit Layout:
FIGURE 11 DSP-002 ANTENNA CONTROL CIRCUIT LAYOUT
Component locations are referenced in decimal fractions of an inch from the lower
left corner with "X" being across and "Y" being up.
59
DSP-002 Antenna Control Circuit Component Locations ( inches):
Item
Number
Name
Value
X Position
Y Position
1
C1
470pF
2.300
0.700
2
C2
1nF
1.850
0.750
3
C4
470pF
1.250
1.100
4
C5
1nF
1.300
1.500
5
C7
470pF
1.650
2.050
6
C8
1nF
2.050
2.050
7
C10
470pF
2.600
1.600
8
C11
1nF
2.600
1.300
9
C13
1nF
1.950
0.250
10
C14
1nF
0.800
1.500
11
C15
1nF
2.025
2.500
12
C16
1nF
3.150
1.325
13
D2
MPN3700
1.650
0.650
14
D4
MPN3700
1.200
1.750
15
D6
MPN3700
2.300
2.100
16
D8
MPN3700
2.750
1.050
TABLE 3 DSP-002 ANTENNA CONTROL COMPONENT LOCATIONS
60