SHORTWAVE CONVERTER
Parts List
C1 Optional capacitor. Try 150pF with 5 Mhz crystal, or 47pF with 8 Mhz
If using crystal � 10 Mhz omit this capacitor.
Omit this capacitor if reception is stronger without it.
C2 33 pF
C3,C5 220 pF
C4 .047 �F
D1 Zener diode, either 5.1v or 6.2v (2N4691 or equivalent)
R1 1K�, � watt resistor
U1 NE602AN Frequency Converter IC
T1 10.7 Mhz miniature IF transformer (green plastic screw)
XTAL 5 Mhz or 8 Mhz crystal, or other values (see text file XTAL.TXT)
One for each band you like to listen to
8-pin DIP socket (for U1)
J1,J2 RCA jacks [J2 is optional, see note 3 below]
Motorola plug (optional). If installing converter externally, use for
connecting cable to car radio's antenna jack). Radio Shack part #274-711
14-pin wire-wrap socket and 14-pin DIP headers for mounting crystals
Optional (see file XTAL.TXT)
Hookup wire
Schematic
=========
����������������������������/\/\/\� +12v
� ����� � � R1
���C3 ���Ŀ xtal � �
��� ����� � �
� ����� � �
J2 (to car radio antenna jack) � � � �
��Ŀ C5 ������������������������� �
� o�������Ķ�������������������Ĵ 7 6 8� �
���� �5 � �
�gnd � U1 � �
� � �
J1 (ant.) ���������Ŀ � NE602 � � � D1
��Ŀ � 3����������Ĵ1 � ����Ĵ�������Ŀ
� o�������Ĵ1 � � � Frequency � � � �
���� � T1 4��nc ���C1*� Converter � � �
� � � ��� � � � �
��������Ĵ2 � � � � ��� �
� � 5����������Ĵ2 � ��� C4 �
� ����������� � 3 � � �
� ������������������������� � �
� � � �
��������������������������������������������������������������������������
�gnd
*see text
�����������������������������������������������������������������������������
Notes:
1) Virtually any construction method (point-to-point wiring, wire wrapping,
etc.) should work, but a printed circuit board is recommended for both
ease and neatness of construction. PC board construction would probably
also help minimize undesirable RF interference from strong local broadcast
stations. See file READ.ME for source of etched PC board. "Universal"
type PC boards, such as the ones available at Radio Shack [part # 276-
170], also work fine. Parts layout is not critical, but keep lead length
short.
2) Connect external antenna to J1 (it works with anything over 2', but better
results are obtained with longer lengths, especially on the lower short
wave frequencies. A 15' "random wire" antenna gives excellent results,
as does an old TV "rabbit ear" antenna.
3) J2 connects to car radio's antenna jack. If mounting the converter inside
the car radio, omit J2 and run a wire directly from where the center
connector of J2 is indicated to the car radio's antenna jack, otherwise
use coax cable to connect from J2 to car radio antenna jack (see note 3).
4) It is suggested that you install the converter inside the chassis of the
car radio (it simplifies the wiring and reduces noise). If you do not have
room to do so, use a metal case for the converter and a short length of
shielded coax cable for the connection from the converter to the car
radio's antenna jack [if you do not wish to use coax, even hookup wire
seems to work o.k., without much noise or interference pick up].
5) Connect +12 volt power input to car radio's on/off switch. That way you
can turn both radio and converter on with that switch.
6) When everything is working, tune in a shortwave station near the middle of
the dial and adjust the slug of T1 for the strongest signal.
7) You may use a signal generator or crystal oscillator to calibrate the
dial, if desired.
8) If using the radio inside a car, hooked to car's 12-volt circuit, you must
use an external antenna going outside the car or you will get no signals.
9) Short wave reception is much better at night on most bands, especially the
lower frequency ones.