You can tune the VCO center frequency to the intended detector frequency without input signal. Observe it at pin 5 with an oscilloscope. Or calculate R and C values according to the datasheet f0 formula at page 8.
Post #1 suggests that something is completely wrong in your setup.
Generally the Morse code CW pitch frequency is about 600Hz. The variable resistor between pins 5 and 6 is part of the RC network that gives the decoded frequency, and is almost impossible to be short (0 ohms) for this frequency.
By definition of its role, LM567 don't need any filter in front of it. The capacitor to the ground on pin 2 gives the bandwidth of the circuit.
Otherwise the best Morse code filter that I ever use, is my brain.
it just works in my case with the values described, and it is broadband, detecting any frequency...
I'm sorry to disappoint you, but if is detecting any frequency, means that doesn't work.
Neazoi;
You are a very experienced and helpful EDAboard member.
You know that to obtain meaningful help, the more information one provides, the better. A schematic diagram, photos of the circuit, waveforms, voltage readings, etc.
According to the LM567 datasheet application note, to get a detected frequency fo = 600Hz (CW pitch) R1 should be 15k and C1 = 100nF (which it is).
With C2 = 1uF the detector Bandwidth is 20%, which should be fine.
If you cannot set R1 to about 15k to decode 600Hz, means that LM567 is dead, or the passive components you use are not good.
Your narrow-band-pass filter may be sufficient, without needing the 567 IC.
Rectify the waveform to become DC pulses. Then attach a smoothing capacitor. Then an invert-gate buffer.
The filter passes a few cycles at a time(dot, dash, whichever). As a result the final output changes state briefly. I believe that substitutes for the function of the 567.
I concur. All it does is replace the incoming signal with a 'clean' one generated in the unit. It may sound nicer but it won't help much in a pile up.
The difference between the two methods is one is an envelope detector, the other is a frequency detector. The LM567 works on the frequency detecting principle, it 'free runs' an oscillator at the pitch you want to detect and attempts to phase lock it with the incoming signal. The bandwidth you choose decides how close the incoming frequency is before it can be 'grabbed' to achieve the lock and it is whether the lock was successful or not that gives you the recovered Morse code.
Brian.
You want it enabled or gated by the output of the PLL lock signal, not triggered by the transition. Use any audio oscillator you want, it is just creating the tone you hear so it can be anything from a 555 to a pure sine according to your preference.All that remains is an adjustable sine AF oscillator that can be triggered on 1 to zero transition out of the 567. Any ideas?
You want it enabled or gated by the output of the PLL lock signal, not triggered by the transition. Use any audio oscillator you want, it is just creating the tone you hear so it can be anything from a 555 to a pure sine according to your preference.
Note that the NE567 has an unusual characteristic that it's bandwidth varies with input level. It will lock over a wider bandwidth when the input signal is larger so for best results keep the input signal as small as practical. You will probably have to experiment to find the best level or maybe fit a pre-set pot at its input to make it adjustable.
Brian.
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