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Over-the-Air (Free TV)
Digital Television Reception

OTA DTV Reception
Digital Television | Improve Reception | Antenna Selection | Receiver Signal Levels | Frequencies

Transmit Tower and Bowtie
DIGITAL TELEVISION (DTV)
DTV requires a stronger signal than analog TV. Additionally most DTV transmitters are in the Ultra High Frequency UHF band (channels 14 -69). These signals are much higher in frequency and are Line-of-Sight -- do not pass through or around objects as signals in the Very High Frequency VHF band (channels 2-13). Also, transmission losses are greater at UHF frequencies. Antennas that picked up analog TV signals will also pick up DTV signals, if the signal is strong enough.

Older TV antennas incorporated a VHF antenna with a UHF antenna, and combined the signals from both antennas into a single cable. Today, most TV antennas are UHF only, and usually smaller.

DTV Channel vs Analog Channel
The old analog TV stations identified themselves by Radio Frequency RF channel, DTV does not. A station's DTV channel may or may not correspond to it's RF channel. Stations that transmitted analog changed their RF channels for DTV, but were allowed to grandfathered in the old channel designation as it's DTV or Virtual Channel.

Because multiple programs (stations) can be broadcast within one RF channel, DTV designations are virtual channel with a dot or dash for sub-channel (69.1 or 69-1). Also see St Louis DTV Stations.

IMPROVE SIGNAL RECEPTION
ANTENNA POINTING DIRECTION: Most DTV signals are in the UHF band and UHF antennas are directional. A UHF antenna must be pointed in the direction of the transmitter tower for best reception. A UHF receive antenna beam is relatively wide, but less forgiving than VHF antennas.

ANTENNA ELEVATION: The antenna should be located as high as possible and clear of obstructions (hills, structures, trees, etc.). The higher the receiving antenna is above the ground level the greater the signal density. In some scenarios range could more than double or triple.
coax and twin lead cables
CABLES: All twin-lead (300 ohm) cables should be replaced with RG-6 coax (75 ohm) cables. Double or triple shielded RG-6 should be used in noisy electronic environments; transmitters, high power lines, transformers or motors. Cable runs should be as short as possible.
RG-6 Cable Loss for UHF Band
Cable Length (feet) 10' 25' 50' 75' 100' 200' 300' 400'
Loss in Range -7% -16% -29% -40% -50% -75% -87% -94%
Signal splitters (1 input, 2 outputs) are equivalent to adding about 55 feet of cable. Long cable runs and multiple splitters may require a booster amplifier. A booster-amp will not improve a weak antenna signal, it amplifies signal and noise, but it will allow for longer cable runs and more splitters.

Older antennas and TV's use a 300 ohm twin-lead connection. In these cases a coax to twin lead adapter (75 to 300 ohm) is required when running coax. The adaptors use an impedance matching transformer to keep signal loss minimal.

PRE-AMP: Pre-amps are low noise amplifiers (amplifies signal but not noise) that mount to the antenna to improve reception. A separate control box inside the home supplies power to the pre-amp through the coax cable center conductor. The control box has a manual gain control and plugs into any power outlet (110 Vac). The pre-amp requires a straight cable run (no splitters) to the control box.
HIGH GAIN ANTENNA: High gain antennas have extended range but narrow beams. These antennas may require a rotor to move the beam (rotate antenna) between stations with a wide angle separation.

SUMMARY


ANTENNA SELECTION
Best performance is achieved when the home antenna has a clear line-of-sight to the transmitting antenna. The higher the home antenna, the stronger the signal density.

RADIO FREQUENCY (RF) BAND:
Television antennas come in 3 basic configurations or frequency band sets; VHF, VHF/UHF, or UHF. Very few DTV transmitters are in the VHF band.
Band RF Channels Frequency
VHF 2 - 13 54 - 216 MHz
VHF/UHF 2 - 69 54 - 216 MHz
470 - 806 MHz
UHF 14 - 69 470 - 806 MHz
ANTENNA GAIN
Reception range doubles for a gain increase of +6 dB, and antenna size will quadruple.
dBD = dBi + 2.15
dBi = dBD - 2.15
ANTENNAS
RECEIVER SIGNAL LEVELS
Analog receivers require a minimum signal to noise ratio (S/N) of 10 - 15 dB, receive signal must be at least 10 - 15 dB above the noise floor. DTV receivers require a S/N of 25 - 30 dB. The noise floor varies with atmospheric conditions, time of day (higher during daylight), and increases in noisy electronic environments; close proximity to transmitters, high voltage lines, transformers or motors, and atmospheric conditions.
DTV Receiver Signal Levels
BAD Marginal Moderate GOOD
Noise Low S/N 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
-84 -71 -65 -59 -53 -47 -41 -35 -29 -23 -17 -11 -5 dBm
-35 -22 -15 -10 -4 2 8 14 20 26 32 38 44 dBmV
0.02 0.08 0.15 0.3 0.6 1.2 2 5 10 19 39 77 154 mV

dBm = decibels with respect to 1 milliwatt
dBmV = decibels with respect to 1 millivolt
mV = millivolts

RF CHANNEL FREQUENCIES
Each RF channel is 6 MHz wide.
TV Channel Frequency Bands
Most DTV Stations in the UHF Band.
TV VHF and UHF bands

UHF Band
Ultra High Frequency
300 - 1000 MHz

RF
Channel
Center
Frequency
MHz
Band-
width
MHz
14 473 470 - 476
15 479 476 - 482
16 485 482 - 488
17 491 488 - 494
18 497 494 - 500
19 503 500 - 506
20 509 506 - 512
21 515 512 - 518
22 521 518 - 524
23 527 524 - 530
24 533 530 - 536
25 539 536 - 542
26 545 542 - 548
27 551 548 - 554
28 557 554 - 560
29 563 560 - 566
30 569 566 - 572
31 575 572 - 578
32 581 578 - 584
RF
Channel
Center
Frequency
MHz
Band-
width
MHz
33 587 584 - 590
34 593 590 - 596
35 599 596 - 602
36 605 602 - 608
37 611 608 - 614
38 617 614 - 620
39 623 620 - 626
40 629 626 - 632
41 635 632 - 638
42 641 638 - 644
43 647 644 - 650
44 653 650 - 656
45 659 656 - 662
46 665 662 - 668
47 671 668 - 674
48 677 674 - 680
49 683 680 - 686
50 689 686 - 692
51 695 692 - 698
RF
Channel
Center
Frequency
MHz
Band-
width
MHz
52 701 698 - 704
53 707 704 - 710
54 713 710 - 716
55 719 716 - 722
56 725 722 - 728
57 731 728 - 734
58 737 734 - 740
59 743 740 - 746
60 749 746 - 752
61 755 752 - 758
62 761 758 - 764
63 767 764 - 770
64 773 770 - 776
65 779 776 - 782
66 785 782 - 788
67 791 788 - 794
68 797 794 - 800
69 803 800 - 806

Ch 37 reserved for radio astronomy.

VHF Band
Very High Frequency
30 - 300 MHz

Use Band-
width
MHz
Government and
Public Service
30 - 50
Amateur Radio 50 - 54
RF
Channel
Center
Frequency
MHz
Band-
width
MHz
2 57 54-60
3 63 60-66
4 69 66-72
Shared Use 72-76
5 79 76-82
6 85 82-88
FM Radio 88 - 108
Air Navigation 108 - 118
Aircraft Voice (AM) 118 - 138
Radar 138 - 144
Amateur 144 - 148
Police / Fire / Ambulance
and Business
148 - 164
Public Service 164 - 174
RF
Channel
Center
Frequency
MHz
Band-
width
MHz
7 177 174 - 180
8 183 180 - 186
9 189 186 - 192
10 195 192 - 198
11 201 198 - 204
12 207 204 - 210
13 213 210 - 216
Radar 216 - 225
Government 225 - 300


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