RF Chat

The Best One Transistor MW Radio Ever

Its a bold statement! Can you do better!

It's the 636 One Transistor Reflex:

And a video from the Internet:

Another example:

Here is my simulation of the 636:

A number of changes were made:

• Modified for 9v and crystal ear-piece output.
• Added a 1k base resistor to stop "Colpitts oscillation".

The schematic consists of:

• On the far left, a the signal generator (before the the signal probe).
• Then the short wire antenna model.
• Then the tuning coil and tap at 10%.
• Then the 636 circuit.

Analysis:

• The left analysis is of a 1 mv 1 Mhz signal modulated by a 1 Khz audio signal.
• The audio shows a square law distorted audio output of 6 mv (a gain of x3).
• The right analysis is of a 10 mv 1 Mhz signal modulated by a 1 Khz audio signal.
• The audio shows a square law distorted audio output of 900 mv (a gain of 45).

Replacing the 1 mH inductor with a 1k resistor, reduced the gain by a factor of 3:

Increasing the tuning coil tap to 20% (from 10%) kills the tuning coil Q.

Over to you!