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Simple TV receiver

Simple TV receiver

When I made FM radio, I could hear the voice signal of first channel of TV. On the frequency slightly lower than that, I could hear the noisy signal of picture of TV. My oscilloscope has Z input. It can display black and white. I made the simple TV receiver. It displays the picture on my oscilloscope.
The signal (comming from the antenna) is amplified and detected. It has the same circuit as a FM radio. But detector of it is amplitude modulation detector. This radio do not have tune control. This machine is able to receiv only the first channel. Receiving frequency is tuned by core of T3. On the (A) point of fig2, I can watch the TV signal indicated on the textbook. See fig 3! I show you the (A) point signal. (A) point signal includes picture signal and horizontal synchronous signal and vertical synchronous signal. Each signals are separated by the signal separator. The famous oscillator IC (555) products the vertical sweep signal. And it is synchronized by the separated synchronous trigger signal. Z input of oscilloscope indicates only black or white. It can not display the gray. It is TTL level input. Therefore the picture on the oscilloscope is only yes or no. It can indicates only the outline of the picture. The Brown tube of oscilloscope is not so bright as that of sold TV set. So I must look it on the dark room.


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