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Old 29th May 2019, 11:33 pm   #4
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 2,106
Default Re: Need a very low power 500Khz working transmitter to send morse code.

There's lots of ways to generate the signals, including a 74HC4060 and crystal(s).

However, as you will be running the transmitter right next to the receiver I would recommend running the signal source at twice the frequency (continuously) but key a flipflop divide by two (74HC74?) as the morse sender ahead of the final stage and LPF. That way, there will be 'nothing' heard in the receiver in the gaps between morse characters, i.e. no constant low level leakage tone if the transmitter is right next to the receiver. Otherwise, you would have to screen the low level stages of the transmitter very well in order to avoid a constant leakage tone appearing in the background in the receiver.
The alternative is to key the oscillator on and off but that will probably sound a bit chirpy and unpleasant.
Regards, Jeremy G0HZU

Last edited by G0HZU_JMR; 29th May 2019 at 11:38 pm.
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