Wednesday, February 13, 2019

TRF radio from a 50's magazine

This is from a 50's magazine. It has a tuner and detector feeding an AF amp. I made a test circuit and tried a couple of my in stock transistors to see how they match the sim. It appears the AC128 is a good match. I only changed the transistors and bias resistors in the series of test.

1 mV will drive my earbud to a good level so it look good. You can use a high Z headphone connected where L5 is.

Adjusting the capacitor values could improve the low response but it is good enough for my ears.

I reversed the transistors and adjusted the bias. The shots are forward and reversed transistors. 

The circuit works both ways but the "proper" hookup has about twice the output. When I rotated the transistors I did need to change the bias. This will be my AF amp for the 50's receiver. I need to put a tuner ahead of it.

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