ECC86 radio, antenna feeding

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neazoi

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Hello,
I consider this little radio attached. I would like to know why the antenna is fed at the center of the coil instead of the top?

What are the pros and cons of this?
 

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Yes, LC is the only part that select which station that is received. It would not be stable or selective if antenna, with frequency depending undefined and unstable impedance load would be a dominant part of the tuning circuit.
Triode load is low and almost constant.
It is possible that antenna is better matched but it depends on how antenna is designed.
 

An old fashioned "dummy aerial" is basically 400 ohms in series with the signal generator output, so long wire aerials are roughly this impedance. Once you have this set completed, I would be tempted to wind 5 or 10 turns of wire on the earthy end of your coil, earth one end of this and connect the aerial to the other. This will raise the Q of the tuned circuit and it might work better.
Frank
 

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