Manual

-131-
T
his circuit is a simplified but effective code
transmitter similar the kind used by military and
amateur radio operators around the world. As the key
i
s pressed and released, the transmitter turns on and
off in sequence.
The code send out by the transmitter can be received
using an AM radio. The radio should be tuned to a
weak station. When the transmitter signal mixes with
the station’s signal it produce an audio tone, called a
beat note. The code signal transmitted is the beat
note you hear on the radio. Use the tuning capacitor
to tune this transmitter until you can hear the beat
note in the radio when you press the key.
If your communications receiver has a beat
frequency oscillator (BFO), you can receive the
carrier wave (CW) signal of this transmitter on a
communications receiver, without tuning to another
station,. The BFO beats with your transmitter’s CW
signal and produces the tone.
The frequency of this oscillator sends out an RF
signal because is very high (500,000Hz to
1,600,000Hz). Tuning to a weak AM station first, then
sending a signal slightly off from the station
frequency, you can hear the beat note that you
produced.
This type of transmission and reception of CW
signals is very efficient and most reliable type of
transmission for some emergencies. You might find
that you do not need an antenna or only 1- 3 feet
(about 60-90 cm) of wire.
N
otes:
EXPERIMENT #110: AM CODE TRANSMITTER
Schematic
Wiring Sequence:
o 41-6-11-ANT
o 7-89-110-137
o 8-12-100
o 40-90-99
o 42-79
o 80-109-119
o 121-122
o 124-138
Note: The ANT is the 3-meter long
green wire. Connect the one end
of the wire to the spring and
hang the wire up vertically.
EP-130_62315RevC.qxp_EP-130_062812 6/23/15 11:18 AM Page 131