Quote:
Originally Posted by WM6
Which filter do you mean?
This is multi-band receiver with selective tuned band, which is some sort of filtering.
You do not need filter here, or you need multi-filter (not worth all efforts). But you need good sine transmitter.
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It appears that the readers of this circuit do not understand it is simply a toy to experiment with and learn the directional properties of ferrite antennas.
But they want a narrow band tuner. Why? Who knows?
I think if they want a narrow band tuner, then they should select the narrow band that they want to investigate, and then build a new design narrow band tuner to listen for the frequency they want to hear. This circuit is a waste of time to modify to become a narrow band receiver.
Maybe we need a new circuit that uses a crystal clock with digital divider and PLL to select desired frequency, then a narrow band adjustable notch filter to find the exact frequency that the receiver will tune to. Then we should also have a bank of capacitors and matched ferrites for each band, which can be adjusted 20-30% within the band by the digital logic and notch filters in combination with adjustable capacitors.
Maybe 20 frequency bands would be good to start with.
Then we can add more ferrite-capacitor antennas to get more frequency bands when we find that none of the 20 initial bands find treasure.
What do you think?
Are we ready for a new circuit design?
Best Wishes,
J_P