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ADDITIONAL COIL WINDING INFORMATION
Your shortwave radio can be operated at frequencies
ranging from 4.5 to about 50MHZ depending on the number
of turns in the coil. A chart is given below which indicates
the number of turns required for a given frequency of
operation. Construct the coil as shown in the step by step
instructions but with the number of turns required for the
Frequency
4.5-7 MHz
6-10 MHz
9-14 MHz
13-20 MHz
19-28 MHz
26-50 MHz
POWER SUPPLY
For more permanent use you can completely eliminate the
need for batteries with the AC-DC power supply kit #28-104.
It supplies either 6 or 9 volts DC for most of the Science Fair
Kits as well as most transistor radios, tape recorders, and
phonographs. Complete connections are shown below.
SHORT WAVE RADIO
28-110
FIG. 2 – SCHEMATIC
Coil Turns
AC/DC POWER SUPPLY
28-104
A8
A12
A10
F16
I16
frequency desired. For the larger coils cellophane tape can
be used to hold the coil together. Different frequencies or
operations have better reception depending on the time of
day. Included below is additional information which shows
the best time to listen to the frequency that you are
interested in.
46
25
15
8
5
2
AMPLIFIER CONNECTIONS
If you wish to use a speaker with your radio it is necessary
to use additional amplification. Ideal for the purpose is the
Science Fair OTL Amplifier #28-106 and the Science Fair
Extension Speaker #28-123. It is necessary to couple the
radio to the amplifier with a dropping transformer #273-2378.
The unit will probably work better in this condition if resistor
R-11 is removed. Complete connections are shown below.
SHORT WAVE RADIO
28-110
RADIO
SHACK
9 Volts
EXTENSION SPEAKER
28-123
SHORT WAVE RADIO
Best Reception Time
Late night
Night often sunset
Late afternoon-night
Morning-afternoon
Morning-early afternoon
Morning
OTL AUDIO AMPLIFIER
28-106
G1
L1
10K
2K
6 Volts
AUDIO TRANSFORMER
C15
H15
L16
L13
RADIO SHACK
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