Amplitude modulation using using BC107 transistor

[mkbh_10]

Homework Statement

In my electronics practical class, i assemble a ckt of amplitude modulation using BC107 transistor ,but the modulated wave always has the same phase up and above , there is no phase difference b/w the upper and lower part of the wave .

My teacher also couldn't understand the problem . I made the ckt 3-4 time but same result .

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[Redbelly98]

If you don't post a circuit schematic, there's not much people here can do to help.

 

[schroder]

Sounds to me like non-linearity. Do you have the bias point set for class-A operation?