555 telegraph

[andrewfarfasha]

is it possible to design a wireless transmitter that transmit morse code using a 555 pin or the frequency generated by the 555 wont be enough to transmit the signal? thanks in advance

Andrew

 

[ke5frf]

There are two types of "legal" Morse Code transmission, A1A continuous wave(unmodulated carrier) and A2A (modulated carrier).

A1A continuous wave requires a beat frequency oscillator at the reciever. The transmitting station is "technically" modulating the carrier by on/off keying it...but the only frequency applicable is the frequency of the carrier and the frequency of the keying (speed and duration). The receiver detects the carrier and the BFO generates an audible tone. This is the most efficient, narrow-band mode. It is the prefered mode for Morse Code.

A2A is an amplitude modulation mode where the audible frequency is modulated onto the carrier by the transmitter, and then demodulated by the superhet reciever with IF and AF stages. Same principle as voice tranmission, except that the transmitter is still "on/off keyed". This is a broadband mode and very inefficient use of spectrum. A2A is very uncommon.

And then of course Morse Code can be transmitted over FM, as is done with ham radio repeaters for station identification, as an injected/modulated audible tone. This is also an inefficient way to transmit Morse Code. Technically it falls under F3E (FM telephony) and isn't considered a mode in itself. FM is never used for dedicated Morse code because it is a broadband modulation scheme.

If you want to transmit Morse Code, you need to investigate building a BFO type reciever and a carrier keying transmitter with a sidetone circuit. You need to also learn about key-click rise and fall times and the consequences of fourier harmonics.

In other words, do not try to reinvent the wheel here, investigate known methods of Morse Code transmission. I suggest a copy of the ARRL handbook as a guide.

 

[Miles Prower]

is it possible to design a wireless transmitter that transmit morse code using a 555 pin or the frequency generated by the 555 wont be enough to transmit the signal? thanks in advance

Andrew

Been there; done that. The triple fiver is a longwave CW/FM QRP rig on a chip. It includes provisions for FM, and also has a "strobe" line that serves nicely for keying. The one bug-a-boo is that there is no provision for shaping the keying waveform, so the CW note will be a bit "clicky", but it's still not too bad. The 555 includes a fairly stiff Class D output stage that's rated to source/sink 200mA.

I use this to test longwave receivers, and for that, you neither need nor is it desirable to have a highly efficient antenna. Still, I can hear the test signal from distances up to a half mile.

Longwave Test Beacon Schemo.

Tuned Loop Antenna

Mod for "Foxhunts"