Elenco Electronics EP-130 - AM Code Transmitter

-131
-
This circuit is a simplified but effective code transmitte
r
s
imilar the kind used by military and amateur radio
operators aroun
d
t
h
e wor
ld
.
A
s t
h
e
k
ey
i
s presse
d
an
d
released, the transmitter turns on and off in sequence.
The code send out b
y
the transmitter can be receive
d
u
sin
g
an AM radio. The radio should be tuned to a
wea
k
stat
i
on.
Wh
en t
h
e transm
i
tter s
ig
na
l
m
i
xes w
i
t
h
the station’s signal it produce an audio tone, called a
beat note. The code si
g
nal transmitted is the beat not
e
you hear on the radio. Use the tuning capacitor t
o
tune this transmitter until you can hear the beat not
e
i
n t
h
e ra
di
o w
h
en you press t
h
e
k
ey
.
I
f
your communications receiver has a beat
f
requenc
y
oscillator (BFO), you can receive the carrier wave
(C
W) signal of this transmitter on a communications
receiver, without tuning to another station,. The BFO
beats with your transmitter’s CW si
g
nal and produce
s
t
h
e tone.
The frequency of this oscillator sends out an RF signa
l
because is very high
(
500,000Hz to 1,600,000Hz
).
Tunin
g
to a weak AM station
f
irst, then sendin
g
a
s
ignal slightly o
ff
f
rom the station
f
requency, you ca
n
hear the beat note that
y
ou produced.
This type of transmission and reception of
C
W signal
s
is very efficient and most reliable type of transmissio
n
for some emer
g
encies. You mi
g
ht find that you do no
t
need an antenna or only 1- 3 feet
(
about 60-90 cm
)
o
f
w
i
re.
No
t
es
:
EXPERIMENT #11
0
: AM
CO
DE TRAN
S
MITTE
R
Schematic
W
iring Sequence:

4
1-6-11-ANT

7-89-110-137

8
-12-100

40
-
90
-
99

4
2-79

80
-
109
-
119

121
-
122

1
24-138