Quote:
Originally Posted by Shark Bait
I have to say that I am still unimpressed with home spun AM radios. No matter what I do there is no way to avoid listening to three stations at the same time.
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This is a failing of all simple tuning circuits. To get station discrimination (high selectivity) with a single tuned circuit you need a very high "Q" (quality).
The "Q" is degraded by the loading on the circuit caused by needing to couple the output of a simple crystal set to headphones for example and still get enough signal to hear. That is why high impedance headphones are specified and crystal sets were never very selective.
In a simple radio circuit eg one transistor the selectivity and gain of the circuit can be made regenerative (feed the output back to the input to re-amplify it). This has the effect of raising the "Q" to a very high figure. However the control of the amount of feedback to avoid uncontrolled regeneration (oscillation) is quite fiddly.
Barry