Digital Television
Antennas and Reception
Over-the-Air Free TV

Digital TV | Improve Reception | Antennas | Signal Levels | Summary | Installation | Frequencies


Digital television (DTV) requires a stronger signal than analog TV. Additionally, most DTV transmitters are in the Ultra High Frequency UHF band (channels 14 - 51). These signals are 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 (or HDTV - High Definition TV) signals, if the signal is strong enough.

DTV, RF and Analog Channels
The old analog TV channel identification used the transmit frequency channel number, usually called the Radio Frequency RF channel, DTV does not (always). A station's identifing DTV channel may or may not correspond to it's RF transmit channel. Most analog TV stations changed their RF channel for DTV, but were allowed to keep their old analog channel identification as their 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.

Virtual (displayed)
DTV Channel
RF Channel
May or May Not
be RF Channel
2 - 13 VHF
14 - 69 UHF

Callsign Suffixes (Show / Hide...)

Over-the-Air (OTH) digital television can broadcast sub channels in high definition (720p or 1080i) or standard definition (480i) resolution. Some sub-channels are audio only. The "p" in the resolution stands for Progressive, picture lines are displayed one after the other. An "i" stands for Interlaced, odd picture lines displayed then even lines.

Cable and satellite operators often compress local broadcast channels before re-broadcasting. Compressing signals opens up more bandwidth and allows for more channels nobody watches. The compression reduces picture quality compared to over-the-air broadcast.

DTV Receivers
Almost all TV's manufactured after 2006 have a built-in digital tuner, or more specifically an ATSC tuner, for receiving over-the-air TV broadcast. HD TV's that do not have an ATSC tuner, and older picture tube TV's, require a Digital Converter Box. The antenna signal plugs into the converter box, which is connected to the TV RF antenna input using coax, or connected using an HDMI cable, or VGA / audio cables, or RCA video (S video) / audio cables, or YPbPr / audio cables. The box formats the signal to the analog NTSC standard.

ATSC - Digital TV standard
NTSC - Analog TV standard

ATSC - Advanced Television System Committee
NTSC - National Television System Committee


Replace all flat twin-lead (300 ohm) and RG-59 coax cables with RG-6 coax (75 ohm) cables. TV coax cables use F-type connectors, F type male connectors on the cable, and female F type connectors on the antenna and TV. Check all outside cable connections for corrosion, replace if necessary. Cable runs should be as short as possible.

All cables cause a signal loss, the longer the cable the greater the loss. Additionally, the higher the frequency, the higher the RF channel number, the greater the loss. Cable loss is measured in decibels (-dB's). Decibels are additive, the loss of two connected cables is the sum of the loss of each cable (add the dB's).

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

Signal Loss
Signal Percent
Range Loss

Signal power (dBm) drops directly by cable loss dB's.

Signal Loss Through Cable
dBm(out) = dBm(in) - Loss (dB)

dBm = decibels with respect to one milliwatt. A negative dBm is dB's below a milliwatt, a positive dBm is dB's above a milliwatt, 0 dBm = 1 mW.

Keep the number of signal splitters to a minimum. A two outputs (2 port) signal splitter cuts the signal in half, introducing a loss of about -3.5 dB for channel 2, and -4 dB for channel 69. A four outputs (4 port) splitter has a loss of about -7 to -8 dB. Adding a 2 port splitter is equivalent to adding about 70 feet of cable, a 4 port splitter is like adding about 140 feet of cable.


Long cable runs and signal splitters may require installing a booster amplifier, increases signal 20 or 30 dB. 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. Most booster amps have an adjustable gain, some are fixed gain, all are powered by house current (110 Vac).

Pre-amps are low noise amplifiers (amplifies signal but not noise) that mount to an indoor or outdoor antenna to improve a weak signal, up to +20 or +25 dB. Signal improvement is the preamp gain minus the Noise Figure, the lower the noise figure the better. The amplifier mounts to the antenna, or as close as possible, for maximum performance. The antenna preamp works with a separate power unit inside the home that supplies power to the amp through the coax cable (center conductor). Most preamps cover the VHF and UHF bands, many have an adjustable gain, most plug into a standard power outlet (110 Vac), some are powered from a USB connection.

Bands: VHF / UHF
Gain: +20 to +25 dB or more
Adjustable or Fixed Gain
Noise Figure: 2 to 4 dB (lower is better)
FM Trap: optional
Power Source: 110 Vac or USB

An FM Trap filters out the commercial FM radio band which is between RF channels 6 and 7. The filter may be needed if an FM signal is strong enough to overpower the preamp or reduce it's automatic gain control. Some traps reduce RF channel 6 reception.


UHF antennas (RF channels 14 - 69) are much smaller than VHF antennas (RF channels 2 - 13) because the wavelengths are shorter. Antenna size is proportional to wavelength, the higher the frequency, the higher the RF channel, the shorter the wavelength and the smaller the antenna. UHF wavelengths vary from about 1 to 2 feet, VHF wavelengths vary from about 5 to 17 feet. Also see Electromagnetic Waves

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

Federal law prohibits restrictions (by governments, community associations, and other entities) that impair the installation, maintenance or use of antennas used to receive video programming. Masts higher than 12 feet above the roofline may be subject to local restrictions. See FCC OTA Reception Devices Rule.

Television antennas come in 3 basic frequency bands, VHF-Lo, VHF-Hi, and UHF. Most antennas are UHF only, some antennas combine the entire VHF and UHF bands (VHF/UHF), and some combine the VHF-Hi and UHF bands (VHF-Hi/UHF).

Band RF Channels Frequency
VHF-Lo 2 - 6 54 - 88 MHz
VHF-Hi 7 - 13 174 - 216 MHz
UHF 14 - 69 470 - 806 MHz

ANTENNA GAIN: The larger the antenna, the more signal captured, the higher the antenna gain, and the more narrow the beam. 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. Most antennas have a positive gain, some smaller indoor antennas have a negative gain. Outdoor antenna gains vary from a few dBi to about +20 dBi at the high end. Most outside antennas have a gain of around +10 dBi.

dBi = dBD - 2.15
dBD = dBi + 2.15

Angle Bearing

Most antennas are directional and must be pointed toward the broadcast tower for best reception. Most UHF antennas have a relatively wide beam ((best reception angles), but are less forgiving (more narrow beam) than VHF antennas. Adjusting an antenna's pointing angle may help pull in weak signals.

Broadcast Tower Angle and Range
Receive Antenna*
Latitude: + ° N
Longitude: - ° W
DTV/RF Ch | Callsign | Angle | Range | Signal(1)
for US broadcast in all 50 states.

* Latitude and Longitude in decimal degrees.

Deg/Min/Sec to Decimal Degrees Calculator (Show / Hide...)

Receive antenna location coordinates (latitude / longitude) can be obtained from most GPS's and smartphones, or see itouchmap.com.

(1) -- The Signal Level (dBm and percent) calculation is an estimate of power delivered to an antenna that is 30 feet above the ground, in an open field, and has a clear line-of-sight to the broadcast tower. The calculation does not account for broadcast tower elevation, antenna height, beam direction, or radio horizon.

Typical variables that effect signal power from a receive antenna (output connector) include, but not limited to;

Beam Loss: 0 to -10 dB
Gain: -3 to +20 dB
Beam Loss: 0 to -10 dB
Terrain / Ground Loss: 0 to -12 dB
Clutter / Obstructions: -1 dB to No Signal
Attic Mount: -3 dB to No Signal
Outside the Broadcast
Radio Horizon:
No Signal

Beam loss occurs when the transmit antenna beam and receive antenna beam are not aligned. Ground loss results from reflections off the ground. Attic mount loss of -3 dB is for a 3/4 inch plywood roof with roofing paper and a single layer of 3 tab asphalt shingles. Metal backed insulation on the attic roof or walls and metal exhaust vents / pipes block signals. Broadcast tower elevation and height determines radio horizon, usually limited to less than 65 miles. Receive antennas beyond the broadcast radio horizon must be mounted higher than usual above the ground, be pointed (fixed or using a rotor) for maximum signal, and usually need a high gain antenna with a preamp.

Also see DTV Reception Maps (dtv.gov/maps).


Digital television receivers will process signals from about -5 dBm (strong) to about -65 dBm (weak).

Signal dBm Percent
Good -5 100%
Normal -35 50%
Weak -55 17%
Minimum Signal -65 0%
Receiver Noise -95
Background Noise -106

Calculate Signal Level to TV
Signal to Antenna: dBm
Antenna Gain:

Cable Length(s): feet
RF Channel:

4 Port Splitters:
2 Port Splitters:

Adapters (75/300 ohm):

Signal from Antenna
Cable Loss
Splitters Loss
Adapters Loss


In almost all cases there is either a good picture and sound, or there is not. There is no difference in picture or sound quality between a good and weak signal. There are some relatively rare instances where the signal power is just strong enough to demodulate and decode, but fades in and out enough to pixelate the picture.

A Pixelated Picture
Signal-to-noise ratio just a little too low
Wide Beam ≈ ≥ 60° / Gain: ≈ -3 to +4 dBi

Wide Beam ≈ ≥ 60° / Gain: ≈20 dBi

Beam: ≈ 60° / Gain: ≈ 5 to 9 dBi

Beam: < 60° / Gain: > ≈ 9 dBi+

Typical Antenna Installation

Outside Antenna Installation
* Ground Block, Surge Protector, or Lightning Arrester
Check local codes for installation requirements and restrictions.

Some installations have an additional ground rod close to the antenna for a little extra safety. The antenna ground wire can be insulated or uninsulated, run inside or outside the home, and be tied into the home power service grounding electrode system near the power meter or fuze / breaker box. The coax Drip Loop allows rain to collect and fall (drip) off the bottom of the loop instead of collecting at the conduit into the home.

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.

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) also called a balun (matching network, typically a ferrite transformer) is required to connect twin-lead to coax. An impedance matching transformer minimizes signal loss. An adapter works both ways, signals go from coax to twin-lead or twin-lead to coax.

-0.2 dB for channel 2
-1 dB for channel 14
-2 dB for channel 69

Type F male/female adapters have a typical loss of -0.5 dB.

Each RF channel is 6 MHz wide.

TV VHF and UHF bands

UHF Band
Ultra High Frequency
300 - 3000 MHz

MHz Band-
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
MHz Band-
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.

No Longer Used for DTV
MHz Band-
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

VHF Lo-Band
MHz Band-
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
VHF Hi-Band
MHz Band-
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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Outdoor Antennas -- Indoor Antennas -- Amplifiers -- Signal Splitters -- Coax -- Installation Hardware