N4YG DDS Code Practice Oscillator Construction The N4YG Code

N4YG DDS Code Practice Oscillator Construction
The N4YG Code Practice Oscillator is a good construction project for a beginner. While
it is not a project which can be completed in a couple of hours, it is not technically
difficult. The most difficult task is preparation of the enclosure. In addition to the N4YG
DDS Code Practice Oscillator Kit, you will need the following:
- Suitable Enclosure (4”x4”x2” LWH or larger)
- 8 to 16 Ohm Loud Speaker (2” Diameter or larger)
- Suitable Key Jack or Jacks
- Suitable Power Jack
- 2 Knobs
- 5 VDC Power Source (Cell Phone Charger works well)
CPO Construction
To construct the N4YG DDS Code Practice Oscillator, follow the following steps.
1.
2.
3.
4.
5.
6.
Construct the board.
Prepare the enclosure.
Mount the jacks, pots and speaker in the enclosure.
Mount the PC board in the enclosure.
Connect the I/O cable (7 wires) and complete chassis wiring.
Connect the wires coming from pins 3 and 4 to convenient sources of ground and
+12 or +13.6 volts.
PC Board Assembly
1. Install 8 1% Digital-to-Analog precision ladder resistors, checking the resistance of
each before forming the leads and placing them on the board. Be careful to match the
resistance value with each position.
R4 – 40K
R7 – 320K
R2 – 10K
R6 – 160K
R1 – 5K
R5 – 80K
R3 – 20K
R8 – 640K
2. Install 4 5% resistors, 1 axial lead capacitor and 1 wire jumper (in the R15 position)
as shown.
Wire Jumper
C3 – 0.1uF
R9 – 47K
R17 – 47K
R12 – 4.7K
R13 – 1K
3. Install the 7-pin header at position JP2, 18-pin DIP socket at position U1 and 8-pin
DIP socket at position U2.
JP2
U1 Socket
U2 Socket
4. Install 3 0.01 uF ceramic capacitors and 2 4.7 uF electrolytic capacitors as shown.
C8 – 0.01uF
C4– 4.7 uF
C1 – 0.01uF
C4– 4.7 uF
C4– 0.01uF
This completes board assembly. The finished board should appear as shown below
except that the 16F88 chip should not be installed until connections have been made to
the transceiver, power applied and the presence of 5 Volts between pins 14 and 5.
When this is verified power should be removed before inserting the 16F88.
Enclosure Preparation
1. Cut all holes required for mounting jacks, pots, the speaker and the PC board.
2. If you wish to have POWER and KEYING indicator leds, these holes should also
be cut, however both of these are optional. These may be mounted on the PC
board from the bottom as shown below, if this option is selected, they should not
be soldered in place until the board is mounted.
3. Mount all the jacks and pots and attach the knobs.
4. Mount the speaker.
Final Connections
1. Rotate both pots fully counter-clockwise. Identify the lugs which have near zero
resistance between then and the center pot lugs. These two lugs will be
grounded. Place wires between these two lugs and also between the ground
connections of all jacks. Do not solder at this time.
2. Connect a wire from the unconnected outside lug of the TONE pot to the +5 volt
terminal of the POWER jack. Solder the end connected to the TONE pot.
3. If you are going to use the LEDs and have them connected to the board, place
their leads through the designated holes from the bottom of the board. The
anodes should go through the holes with the square pads. Do not solder yet.
4. If you are going to use the LEDs, but mount them separate from the PC board,
attach wires to the 4 pads designated for the LEDs.
5. Mount the board in the enclosure and, if the LEDs are present, place them in
their holes in the enclosure and, from the top of the board, solder them in place.
6. Connect the wire coming from pin 6 of J2 to the most convenient of the ground
points. Solder all the ground connections.
7. Connect the wire coming from pin 5 of J2 to the +5 volt terminal of the POWER
jack.
8. Connect the wire coming from pin 3 and 4 of J2 to the two speaker terminals.
9. Connect the wire coming from pin 2 of J2 to the center lug of the VOLUME pot.
10. Connect the wire coming from pin 1 of J2 to the unconnected lug of the VOLUME
pot.
11. Connect the wire coming from pin 7 of J2 to the unconnected lug of the TONE
pot.
12. If the LEDs are panel mounted separate from the board, attach the 4 wires
appropriately.
This completes the construction. You may want to apply power before placing U1 and
U2 in their sockets and check to see that +5 volts is present in the places that it should
be. After applying power, check to see that the CPO gives a tone when keyed and that
the VOLUME and TONE controls operate properly. Then with then with the enclosure
cover on, check the maximum volume. If the volume is less than desired, you may
increase the gain of the audio amplifier by reducing the value of R12 by a several
hundred ohms.
Below is one implementation of the N4YG Code Practice Oscillator. This is just one
example.
JP1
C8
.01
U3
LM78L05
+5V
1
C1
.01
+5V
3
VIN
GND
2
640K
R7
R11
14
80K
R4
40K
R3
R10
5K
47K
C3
.1
5
R14
5K
D2
POWER
KEYED
R19
100
IN
O+
VOL
O-
NC
+5V
R12
4.7K
+5V
R18
100
JP2
R13
1K
5
8
VOL+
VOL-W
SP+
SP+5
GND
TONE-W
1
2
3
4
5
6
7
CPO INTERFACE
6
VSS
+5V
4
C7 +
4.7uF
3
10K
R1
2
7
5K
D1
C5
4.7uF
20K
R2
RA7/OSC1/CLKI
+5V
U2
TDA7052
GND
6
7
8
9
10
11
12
13
C4
.01
VOLUME
GND1
RB0/INT/CCP1
RB1/SDI/SDA
RB2/SDO/RX/DT
RB3/PGM/CCP1
RB4/SCK/SCL
RA5/MCLR/VPP
RB5/SS/TX/CK
RB6/AN5/PGC/T1OSO/T1CKI
RA6/OSC2/CLKO
RB7/AN6/PGD/T1OSI
R9
V+
16
RA0/AN0
RA1/AN1
RA2/AN2/CVREF/VREFRA3/AN3/VREF+/C1OUT
RA4/T0CKI/C2OUT
+5V
.01
1
15
160K
R5
VDD
17
18
1
2
3
4
TONE
C6
320K
R6
U1
16F88
1
2
3
4
SIDETONE INTERFACE
47K
R17
47K
R16
47K
C2
.01
R8
+
R15
47K
VOUT
KEY
STOUT
GND
+12/+5
+12V