[Pahom]

Originally Posted by omar

Hello...

I have been conducting experiments on a signal processor, and here I thank engineer John for this wonderful circuit that he made available to the public for general use. The initial results were very important as follows....

$ - First paragraph It has now become possible to detect very low frequencies with high accuracy and reliability. The triangle wave was tried. Things were excellent and there were no problems with detection....

$ - The second paragraph.... The problems started with the sine and square waves. We found that knowing the main frequency is not enough to detect it...

There is something called the pulse width, spacing, or pulse time, which is A type of primary frequency coding...

(For example)
to detect a 37 Hz sine wave that cannot be detected by relying only on this fundamental frequency, the pulse width must be known to calculate the coding frequency to detect that signal. In normal mode (the main frequency divided by two is the encoding frequency) to detect the main frequency (37/2 = 18.5 Hz)...


As an example, this means when dealing with a sine or square signal, the detector must be set to the encoding frequency, which is 18.5 Hz, to detect the fundamental frequency. 37 Hz outdoors....

In nature, the matter is similar. If the electrical signal is sinusoidal, the frequency and pulse width or spacing must be known to calculate the coding frequency of the signal to be detected. Note that the type of circuit filters controls the frequency pulse width. To overcome this dilemma, an appropriate detection range must be chosen. It contains the fundamental frequency and the coding frequency.

Good afternoon Omar! Following your theory, you propose to take the fundamental transmission frequency and look for a response at the second harmonic. At a low frequency in Hz with lm567 this is a very unstable filter. Maybe then take the Tx frequency at a higher frequency, for example 250 kHz, and receive the receiver at 125 kHz at these frequencies LM567 behaves more stably, although it will also not clearly pass 125 kHz but 125 kHz and 200 Hz above and below 124 kHz and 800 Hz. By the way, how do you expect to extract a useful signal from the desired target? The reflection of Tx will be from all that metal.