Strange TRF reflex AM MW radio circuit.

This is very interesting and funny reflex AM MW radio circuit. Circuit use common base RF preamplifier and emitter follower output audio amplifier.
With trim pot set AM demodulator "best sensitive point". Circuit use silicon diode.

[@radiofun232]

Very interesting circuit with good results, given only 3 transistors!

[@user-io3yy9vp9n]

Marvelous scheme! The RF input is also the AF output! And at the same time, both the input and output have low impedance! Only instead of a choke in the collector of the output transistor, I would install a high-quality LC circuit with a weak transformer connection to the base of the first transistor. This can greatly increase selectivity.

[@ingussilins6330]

Thanks, I think best results with BC547 transistors in KT315 place.
Input transistor works as a common base configuration for RF signal and emitter follower for audio freqencies.
Serries LC tank "love" low input impedance. I think this circuit input's impedance for RF less than 1 ohm.

[@user-io3yy9vp9n]

@@ingussilins6330 You are very mistaken! The resistance of the oscillating LC circuit at the resonant frequency is very high and the higher the higher the quality factor of the circuit. Therefore, such a circuit is perfectly consistent with the collector of a transistor connected according to a circuit with a common base. Therefore, the base of the next transistor should not be connected to the entire circuit, but only to a part of the turns, so as not to shunt the circuit with its input resistance and reduce the sharpness of the peak of its frequency response. Regarding the transistor, any modern high-beta transistor will be better than the obsolete KT315.

[@ingussilins6330]

@@user-io3yy9vp9n This radio use serries LC tank. For paralel LC tank need RF amplifier with hight input impedance, like JFET, FET... For serries LC tank need RF amplifier with low input impedance, like common base circuits or current transformer.
This radio circuit is a reflex radio ( input/output transistor amplify RF and AF )

[@user-io3yy9vp9n]

​@@ingussilins6330 You are in vain explaining to me the principle of operation of your circuit. I perfectly understand the purpose of each element in it. I recognize her uniqueness and genius. It is indeed unique for the same point to be both the input and output of a receiver. But you must also accept rational criticism. The input serial LC circuit may not have sufficient quality factor and will serve more as a bandpass filter. A parallel LC circuit connected to the collector of the input stage transistor will perform much better. In fact, there are many receiver circuits, the input stage of which is made precisely according to a common base circuit. The low input impedance of such a stage perfectly matches the antenna impedance of 50-75 Ohms. And in such circuits, as a rule, the collector resonant circuit of the input stage is tunable. And if this is a fairly common practice, then why not just try it out of curiosity? ;)

[@user-io3yy9vp9n]

@@ingussilins6330 I suspect that you simply did not understand what schema changes I mean. Unfortunately, RUclips comments do not allow sharing pictures.

[@user-io3yy9vp9n]

Це дійсно геніально!

[@Lechoslowianin]

Cool, but I'd give it a variable capacitor and an external grounded antenna

[@user-io3yy9vp9n]

And in the collector of the output transistor, instead of a choke, I would install a high-quality LC circuit with a weak transformer connection to the base of the first transistor. This would greatly improve selectivity.

[@SobatElektronik]

Nice good

[@MAKSMIT-ME]

Антенна нагруженна на катушку динамика , 🤔 , по моему это не лучшее решение , ну а в прочем главное что это успешно работает ☺

[@MAKSMIT-ME]

Ну такого решения я еще не видел

[@ingussilins6330]

Схему нарисовал сам, долго думал, нельзя ли совместить ВЧ усилитель с общей базой с усилителем звука - эмиттерным повторителем. Входное сопротивление усилителя с общей базой менее 1 Ом.

[@MAKSMIT-ME]

Очень не обычно

[@MAKSMIT-ME]

Я тоже записал видео 😀