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Digital Television Reception

OTA DTV Reception
Digital Television | Improve Reception | Antennas | Signal Levels | Frequencies

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, over-the-air 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.

DTV Channel vs Analog Channel
The old analog TV channel identification used the transmit frequency channel number, technically called the Radio Frequency RF channel, DTV does not. A station's DTV channel may or may not correspond to it's RF channel. Most analog TV stations changed their RF channel for DTV, but were allowed to use the old analog channel designation as it's DTV or Virtual Channel identification.

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

Angle Bearing ANTENNA POINTING DIRECTION: UHF antennas are directional, and must be pointed in the direction of the transmitter tower for best reception. A UHF antenna beam is relatively wide, but less forgiving than VHF antennas.

DTV Reception Maps
Enter your location, click on TV station callsign for angle, signal level, etc.

ANTENNA ELEVATION: The antenna should be located as high as possible and have a clear line-of-sight (no hills, structures, trees, etc.) to the transmitting towers. The higher the receiving antenna is above the ground level the greater the signal density.

coax and twin lead cables CABLES: Replace all twin-lead (300 ohm) cables with RG-6 coax (75 ohm) cables. The more shielding (up to quad shielding), the better the immunity from interference (power lines, transmitters, etc). One minor drawback is the more shielding, the less flexible the cable. Check all outside connectors for corrosion, replace if necessary. Cable runs should be as short as possible.

Cable Loss Calculator
RG-6 Coax Cable
Cable Length: feet

Signal Loss (dB)
Range Loss Percent (%)


SIGNAL SPLITTERS: A one input two outputs (2 port) signal splitter cuts the signal in half at the outputs, which is equivalent to adding about 50 feet of cable.

BOOSTER AMPLIFIERS: Long cable runs and splitters may require a booster amplifier. A booster-amp will not improve a weak antenna signal, because it amplifies signal and noise, but it will allow for longer cable runs and more splitters.

PRE-AMPS: Pre-amps are low noise amplifiers (amplifies signal but not noise) that mount to an indoor or outdoor antenna to improve reception. Outdoor pre-amps have a separate power unit inside the home that supplies power to the pre-amp through the coax center conductor. Most have an adjustable gain, most plug into a standard power outlet (110 Vac), some are powered from a USB connection.

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.

ADAPTERS: 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 to connect twin-lead to coax. The adaptors use an impedance matching transformer to keep signal loss minimal. An adapter works both ways, signals go from coax to twin-lead or twin-lead to coax.

ATTENUATORS: A signal that is too strong can overwhelm (saturate) a TV receiver, causing signal distortion (cannot decode signal). An attenuator can reduce the signal to an acceptable level. Some attenuators have a fixed reduction, some are adjustable.

The Best of the Essentials
DTV Antennas and Accessories
Outdoor Antennas -- Indoor Antennas -- Amplifiers -- Signal Splitters -- Coax -- Installation Hardware

SUMMARY
ANTENNAS

Television antennas come in 3 basic frequency band configurations.

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. Antenna gain is expressed in dBi or dBD. Gain expressed in dB is usually really dBD, makes gain look 2 dB higher.

dBi = dBD - 2.15
dBD = dBi + 2.15




Typical Antenna Installation

Outside Antenna Installation
* Ground Block, Surge Protector, or Lightning Arrester
Check local codes for installation requirements and restrictions.
RECEIVER SIGNAL
Analog receivers require a minimum signal to noise ratio (S/N) of 10 to 15 dB, signal must be at least 10 to 15 dB greater than background electromagnetic noise. DTV receivers require a S/N of 25 to 30 dB. Noise floor varies with atmospheric conditions, time of day, and proximity to transmitters and high voltage devices and lines.

Signal Level dBm dBmV mV
Good 100% -5 44 154
90% -11 38 77
80% -17 32 26
70% -23 26 19
Moderate 60% -29 20 10
50% -35 14 5
40% -41 8 2
30% -47 2 1.2
Weak 20% -53 -4 0.6
10% -59 -10 0.3
0% -65 -15 0.15
Noise -84 -35 0.02

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 VHF and UHF bands

UHF Band
Ultra High Frequency
300 - 3000 MHz

RF
Channel
MHz Band-
width
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
MHz Band-
width
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
Ch 37 reserved for radio astronomy.

RF
Channel
MHz Band-
width
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

VHF Band
Very High Frequency
30 - 300 MHz

RF
Channel
MHz Band-
width
Government and Public Service 30 - 50
Amateur Radio 50 - 54
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
MHz Band-
width
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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