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This chapter is from the book

3.5 Cable TV Channel Allocation Scheme

The in-house coaxial cable wiring carries many channels of TV signals. The conventional TV VHF channels, channels 2 to 13, occupy frequencies from 54 to 216 MHz with frequency gaps in between for FM broadcast stations. The off-the-air UHF channels, channels 14 to 69, occupy frequencies from 470 to 806 MHz. Table 3.4 shows frequency arrangement for off-the-air TV channels.

This TV channel frequency arrangement is regulated by Part 73 (Radio Broadcast Services) of FCC rules and regulations, which is labeled as CFR title 47 [1]. Channel 37, occupying 608 to 614 MHz, is reserved exclusively for the radio astronomy service. Many off-the-air digital TV channels have been allocated in the UHF frequency band for the analog-to-digital transition period. Detailed information, including location and channel numbers, can also be found in the recent Part 73 document.

Table 3.4. Numerical Designation of Off-the-Air Television Channels.

VHF Channel No.

Frequency Band (MHz)

UHF Channel No.

Frequency Band (MHz)

UHF Channel No.

Frequency Band (MHz)

2

54–60

14

470–476

38

614–620

3

60–66

15

476–482

39

620–626

4

66–72

16

482–488

40

626–632

5

76–82

17

488–494

41

632–638

6

82–88

18

494–500

42

638–644

7

174–180

19

500–506

43

644–650

8

180–186

20

506–512

44

650–656

9

186–192

21

512–518

45

656–662

10

192–198

22

518–524

46

662–668

11

198–204

23

524–530

47

668–674

12

204–210

24

530–536

48

674–680

13

210–216

25

536–542

49

680–686

   

26

542–548

50

686–692

   

27

548–554

51

692–698

   

28

554–560

52

698–704

   

29

560–566

53

704–710

   

30

566–572

54

710–716

   

31

572–578

55

716–722

   

32

578–584

56

722–728

   

33

584–590

57

728–734

   

34

590–596

58

734–740

   

35

596–602

59

740–746

   

36

602–608

60

746–752

   

37

608–614

61

752–758

       

62

758–764

       

63

764–770

       

64

770–776

       

65

776–782

       

66

782–788

       

67

788–794

       

68

794–800

       

69

800–806

Cable TV channels share the same frequency arrangement as off-the-air TV only for channels 2 through 13. Immediately above the frequency of channel 13, cable TV channels occupy a continuous frequency band from 210 up to 552 MHz for channel numbers of 23 to 78. Cable TV channels 14 to 22 occupy a frequency band from 120 to 174 MHz merging to the frequency band of conventional TV channel 7. There is no conflict with the FM broadcast service because cable TV signals are contained within coaxial cables. This channel allocation plan is set forth in the EIA's ''Cable Television Channel Identification Plan, EIA IS–132, May 1994'' (EIA IS–132) [2]. Table 3.5 shows this channel frequency arrangement. Other regulation for the cable TV industry is provided by Part 76 (Cable Television Service) of FCC rules and regulations which is labeled as CFR title 47 [3].

Above channel 78 starting at 552 MHz, 33 digital cable channels can be allocated for a frequency band of up to 750 MHz. Digital cable channels can be used for cable modem as well as digital TV services. It is expected that the video carrier of a cable TV channel should have a signal strength of around 0 dBµV at an impedance of 75 ohms.

Table 3.5. Numerical Designation of Cable Television Channels

Channel No.

Frequency (MHz)

Channel No.

Frequency (MHz)

Channel No.

Frequency (MHz)

Channel No.

Frequency (MHz)

2

54–60

14 (A)

120–126

37 (AA)

300–306

54

402–408

3

60–66

15 (B)

126–132

38 (BB)

306–312

55

408–414

4

66–72

16 (C)

132–138

39 (CC)

312–318

56

414–420

5

76–82

17 (D)

138–144

40 (DD)

318–324

57

420–426

6

82–88

18 (E)

144–150

41 (EE)

324–330

58

426–432

7

174–180

19 (F)

150–156

42 (FF)

330–336

59

432–438

8

180–186

20 (G)

156–162

43 (GG)

336–342

60

438–444

9

186–192

21 (H)

162–168

44 (HH)

342–348

61

444–450

10

192–198

22 (I)

168–174

45 (II)

348–354

62

450–456

11

198–204

23 (J)

216–222

46 (JJ)

354–360

63

456–462

12

204–210

24 (K)

222–228

47 (KK)

360–366

64

462–468

13

210–216

25 (L)

228–234

48 (LL)

366–372

65

468–474

   

26 (M)

234–240

49 (MM)

372–378

66

474–480

   

27 (N)

240–246

50 (NN)

378–384

67

480–486

   

28 (O)

246–252

51 (OO)

384–390

68

486–492

   

29 (P)

252–258

52 (PP)

390–396

69

492–498

   

30 (Q)

258–264

53 (QQ)

396–402

70

498–504

   

31 (R)

264–270

   

71

504–510

   

32 (S)

270–276

   

72

510–516

   

33 (T)

276–282

   

73

516–522

   

34 (U)

282–288

   

74

522–528

   

35 (V)

288–294

   

75

528–534

   

36 (W)

294–300

   

76

534–540

           

77

540–546

           

78

546–552

For delivering cable modem services, a reverse channel is required to send user command or information back to the head end. The frequency band below the conventional TV channel 2 has been allocated for reverse channels. There is one convention called sub-split where the reverse channel has a frequency band of 5 to 30 MHz. There is another convention called expanded sub-split where the reverse channel frequency band is from 5 to 42 MHz. Reverse channels in the frequency range between 25 and 37 MHz have been proposed by the IEEE 802.14 study group for a cable modem standard. The recommended reverse channel signal strengths are in the range of 5 to 55 dBµV or to 58 dBµV for sub-split or expanded sub-split, respectively.

The majority of the frequency band on existing in-house wiring has been occupied by cable TV channel allocations. CEBus [4] has recommended a dual coaxial cable wiring system to carry local video signals as well as data traffic. In case a second coaxial cable is not available, the frequency band between the upper edge of reverse channel at 42 MHz and the lower edge of TV channel 2 at 54 MHz can be used to establish a coaxial cable–based home network. This coaxial cable–based home network should not interfere with either TV channels or reverse channels by minimizing out-of-band energy at 60 dB below these TV or reverse channel signals.

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