This
project arises from a twofold need connected with CW learning, first of
all to enance the performance of the traditional oscillator providing
it with a display on wich you can verify the correctness of your keying,
and then the need to have an instrument you can couple to the receiver
so as to help those who, being still novices, are in a great trouble trying
to deal with their early CW QSOs.
The decoding capabilities are essentially connected to the received signal
quality, it must by clear and strong enough, so don't think you can decode
a weak and vanishing signal in the QRM, if this is your goal, you should
much better make use of your ears. If however the signal is good and stable
enough, then this equipment can succeed in doing its job well, adapting
also itself to the CW rate, provided that it is sufficiently regular.
The device is equipped with a 2x16 LCD display , the text shifts from
left to the right starting from the end of the second raw. An inter-words
automatic spacing function is provided, based on a regular timing of the
pauses in the sent code. This function may be inhibited grounding the
J pin if the device is used for training purpose or while receiving an
improperly sent code. The audio input must be at
least 100 mV pp, a clipper is provided to cut large signals. The band
width is about 100 Hz and the center frequency may be adjusted between
700 and 1000 Hz by a trimmer. A service push button displays the keying
rate in chars/min, this measure is refreshed every N received characters.
An input is provided for a straight Key, and both inputs (audio and key)
activate the code display and the audio monitor function, a LED is operative
while receiving code and shows the correct lock to the audio input, these
two monitoring functions are very helpful to adjust the receiver tune
because of the narrow bandwith of the decoder. The BF monitor can drive
a 32 Ohm earphone with the two sides series connected. The Vcc can be
supplied by a 9V transistor battery and requires about 15 mA. An external
supply (min 9V) is however recommended for long time use.
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