Assignment 3

Color Television Picture Tube

Diagram of Color CRT© http://www.danalee.ca/ttt/monitors_and_television_sets.htm

How it Works

Colored picture tubes have two kinds of fluorescent screen structures, known as the dot phosphor, and the strip phosphor. In both cases, the chemical compounds that convert electron-beam energy into light of the additive primary colors (red, green, blue), are deposited on the inner face of the glass picture tube in precision arrangements in dots or stripes of alternating colors.

At the rear of the picture tube is the electron gun, which produces three separate beams of electrons. These three beams hit the colored dots, and the tube is so designed that each beam can hit dots of only one color; a mask prevents each beam from striking the others' color dots.

Because the colored dots are so small that they cannot be seen separately by the viewer, the effect is three superimposed images in the primary colors. By adjusting the strength of the respective beams of electrons, the relative brightness of the image produced by each can be changed. (Adapted from Monitors and Television Sets, Color Picture Tubes, ©danalee.ca/ttt/monitors_and_television_sets.htm)

ASSINGMENT 2

GENERAL TELEVISION FREQUENCIES

Sub CATV Band - T7 - T13 7 - 58 MHz

VHF Band - Ch. 2 – 13 54 - 216 MHz

Low Band - VHF Ch. 2 – 6 59 - 88 MHz

Mid Band - UHF Ch. 14 – 22 121 - 174 MHz - UHF Ch. 95 – 99 91 - 120 MHz

High Band – VHF Ch. 7 – 13 175 - 216 MHz

Super Band - CATV Ch. 23 – 36 216 - 300 MHz

Hyper Band - CATV Ch. 37 – 62 300 - 456 MHz

Ultra Band - CATV Ch. 63 – 158 457 - 1002 MHz

UHF Band Ch.14 - 83 - CATV Ch. 63 – 158 70 - 1002 MHz

VHF TELEVISION FREQUENCIES

BAND CH # FREQUENCY

VHF LOW 02 54-60 MHz

VHF LOW 03 60-66 MHz

VHF LOW 04 66-72 MHz

VHF LOW 05 76-82 MHz

VHF LOW 06 82-88 MHz

VHF HIGH 07 174-180 MHz

VHF HIGH 08 180-186 MHz

VHF HIGH 09 186-192 MHz

VHF HIGH 10 192-198 MHz

VHF HIGH 11 198-204 MHz

VHF HIGH 12 204-210 MHz

VHF HIGH 13 210-216 MHz

UHF TELEVISION FREQUENCIES

CH #FREQUENCY CH #FREQUENCY CH #FREQUENCY

14 470-476 MHz 38 614-620 MHz 62 758-764 MHz

15 476-482 MHz 39 620-626 MHz 63 764-770 MHz

16 482-488 MHz 40 626-632 MHz 64 770-776 MHz

17 488-494 MHz 41 632-638 MHz 65 776-782 MHz

18 494-500 MHz 42 638-644 MHz 66 782-788 MHz

19 500-506 MHz 43 644-650 MHz 67 788-794 MHz

20 506-512 MHz 44 650-656 MHz 68 794-800 MHz

21 512-518 MHz 45 656-662 MHz 69 800-806 MHz

22 518-524 MHz 46 662-668 MHz 70 806-812 MHz

23 524-530 MHz 47 668-674 MHz 71 812-818 MHz

24 530-536 MHz 48 674-680 MHz 72 818-824 MHz

25 536-542 MHz 49 680-686 MHz 73 824-830 MHz

26 542-548 MHz 50 686-692 MHz 74 830-836 MHz

27 548-554 MHz 51 692-698 MHz 75 836-842 MHz

28 554-560 MHz 52 698-704 MHz 76 842-848 MHz

29 560-566 MHz 53 704-710 MHz 77 848-854 MHz

30 566-572 MHz 54 710-716 MHz 78 854-860 MHz

31 572-578 MHz 55 716-722 MHz 79 860-866 MHz

32 578-584 MHz 56 722-728 MHz 80 866-872 MHz

33 584-590 MHz 57 728-734 MHz 81 872-878 MHz

34 590-596 MHz 58 734-740 MHz 82 878-884 MHz

35 596-602 MHz 59 740-746 MHz 83 884-890 MHz

36 602-608 MHz 60 746-752 MHz

37 608-614 MHz 61 752-758 MHz

Reference:

•  Television Frequency Table, Copyright© 1973 – 20072007, http://www.csgnetwork.com/

ASSINGMENT 1

TELEVISION BLOCK DIAGRAMS AND FUNCTIONS

Functions of different blocks of a TV

The Black and white TV receiver has a simple circuit block diagram compared with the colour receiver. The following details describe the function of each block.

1. Tuner Unit - This section contains the RF Amp for both UHF and VHF, the Mixer, local oscillator and AFT. The RF amp amplifies the signal from the antenna, reduce the noise before passing it to the mixer which converts it into IF with the local oscillator. The AFT gives the user the option of fine tuning. This controls the local oscillator and RF amplifier circuits in the tuner.
2. RF Amplifier – This receives the Video and Audio signal from the aerial and amplifies it.
3. Mixer – This comprised of an integrator which mixes the received signal with the output from the local oscillator and to form the Intermediate Frequency.
4. Local Oscillator – This provides a frequency that is mixed with the incoming RF signal.
5. IF Amplifier – This amplifies the tuner output and regulates the local oscillator within the tuner through the automatic frequency control.
6. Demodulator – This section converts the Intermediate frequency into the original transmitted signal which comprises of both video and Audio signals
7. Video Amplifier –This section amplifies the video signal and passes it to the CRT to control the brightness at each particular point of the screen.
8. Sync Separator –This separates the synchronized vertical and horizontal sweeps of the video signal and each respective signal is directed to its timebase.
9. Horizontal Timebase –This Section Provides a saw toothed signal that will sweep across the CRT vertically for horizontal detail of the Picture. The signal is controlled by the sync separator.
10. Vertical Timebase - This Section Provides a saw toothed signal that will sweep across the CRT horizontally for vertical detail of the Picture. The signal is controlled by the sync separator.
11. The Extra Tension Voltage -This is a very high voltage that is controlled by the time bases for running the final anode of the CRT.
12. The IF amplifier and Modulator - This section receives the filtered audio signal IF and converts it to its original frequency and the transmitter.
13. Audio Amplifier – This section amplifies the modulated audio signal and drives the speaker.
14. Power Supply – This block provides a DC voltage to all functional blocks. A previous Voltage is generated for the EHT voltage supply to the CRT.
15. CRT – The Cathode Ray Tube receives a modulated video signal and with an internal electron beam which is controlled by the time bases changes the brightness at each point of the screen to give out the intended

Block diagram of a TV

Reference:

• Color Television, http://www.tdk.co.jp/teapl01/ctv ,©1996-2007 TDK Corporation. All rights reserved.

• Mono TV Receiver©http://www.hobbyprojects.com/block_diagrams.html

• Alvin A. Liff, J.A. Sam Wilson, Color and Black and White Television, Theory and Servicing, 3^rd Edition©1993 Prentice Hall Inc. upper Saddle River, NJ 07458