Quote:
Originally Posted by Geo
Maybe nothing special... but it is n't a tape recorder.
Preamplifiers of tape recorders have filters so to work according to the NAB curve.
We need a flat curve.
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The mineoro LRL receivers, like the two box detectors, are super regenerative receivers, and the frequency response is not flat. If the input oscillating LC circuit is tuned to 40khz for example, it will have its maximum sensitivity for frequency between 35 to 45khz. Pre-amps for tape deck, they are well-designed circuits with high gain and low noise, but they have a wide passband, reproducing from a few hz to about 20khz, and this is not good because there would be a lot of interference from the electrical network and its harmonics . The phenomenon apparently occupies a large spectrum of frequencies, and the secret is to choose an interference-free frequency, and design a sensitive receiver for that band with a narrow passband. If the receiver has a flat response, it will be immune to a lot of interference, being forced to reduce the circuit gain to not give false signals.