Solid State Shortwave Receivers For Beginners - The Listeners Guide

Components List for Fig.35
R1 1.5k
R2 3.3k
VR1 50k lin. carbon
VR2 1k lin. carbon.
I.C. NE55SV.
C1 47nf plastic foil.
C2 100mfd. 10v.w.
Speaker (or headphones).
Morse key.
Hardware.
it is extremely useful for anyone interested in amateur band
communications to be able to read morse code as this mode of transmission
is quite widely used, and is very effective. Also, if one wishes
to obtain a transmitting licence for the S.W. amateur bands, it is necessary
to first pass a morse test (and the Radio Amateurs Examination).
The morse code is given below.
A a B b C c D d E e F f G g H h
I i J j K k L l M m N n O o P p
Q q R r S s T t U u V v W w X x
Y y Z z 1 1 2 2 3 3 4 4 5 5 6 6
7 7 8 8 9 9 0 0 Fullstop . Comma ,
? ? - - : :
If a dot is taken to equal one unit, a dash is three, the space
between individual characters of a letter is one, the spacing between
letters is three, and the spacing between words is seven. It is best not
to think of the code in terms of dots and dashes, but think of it in
terms of sounds. For instance, many people find it helpful to think
of dots as being the sound dit and dashes as the sound dah. Thus one
would not think of the letter C as being dash dot dash dot, but as
dah dit dah dit. The latter flows much better than the former, and its
rhythmic character tends to be much more easily remembered.
Calibration Oscillator
In Order to provide a calibrated tuning dial for a completed
receiver, some form of calibration oscillator is required. Crystal
calibration oscillators are frequently used, but these are expensive and
provide a degree of accuracy that isnot required even when calibrating
a quite sophisticated receiver, let alone a simple one. The calibration
oscillator described here is therefore of the L - C type. Its circuit
diagram is shown in Fig.36.
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