|DIGITAL TELEVISION (DTV)|
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, 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 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.
All Over-the-Air (OTH) television broadcast are digital, many have a sub-channel that is high definition resolution (720p or 1080i), and one or more standard definition (480i) sub-channels. 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.
|IMPROVE SIGNAL RECEPTION|
Replace all twin-lead (300 ohm) cables with RG-6 coax (75 ohm) cables. Multiple shielded RG-6 has better immunity from interference, is more sturdy and durable, but is less flexible. 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. 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
Signal Loss in Decibels (dB)
Signal power (dBm) drops directly by cable loss dB's.
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 -3.2 dB. A four outputs (4 port) splitter has a loss of about -6.4 dB. Adding a 2 port splitter is equivalent to adding over 50 feet of cable, a 4 port splitter is like adding over 100 feet of cable.
SYSTEM LOSS CALCULATOR (Show / Hide...)
Long cable runs and signal splitter(s) 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. The amplifier mounts to the antenna and works with a separate power unit inside the home that supplies power to the amp through the coax cable (center conductor). Most have an adjustable gain, most plug into a standard power outlet (110 Vac), some are powered from a USB connection.
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).
|VHF-Lo||2 - 6||54 - 88 MHz|
|VHF-Hi||7 - 13||174 - 216 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. 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.
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.
ANTENNA POINTING ANGLE
Most antennas are directional and must be pointed toward the transmitter 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.
Receive antenna location coordinates (latitude / longitude) can be obtained from most GPS's and smartphones, or go to itouchmap.com.
(1) Signal Level basis (Show / Hide...)
CONVERT TO DECIMAL DEGREES CALCULATOR (Show / Hide...)
DTV Reception Maps (dtv.gov/maps)
|TELEVISION RECEIVER SIGNAL|
Digital television receivers will process signals from about -5 dBm (strong) to about -65 dBm (weak).
|Good||-5 to -35|
|Normal||-35 to -55|
|Weak||-55 to -65|
|Low Signal-to-Noise||-65 to -95|
|Calculate Signal Level to TV|
|Signal to Antenna:||dBm|
|4 Port Splitters:|
|2 Port Splitters:|
Antenna Signal (dBm)
INDOORs (with Preamp)
Some installations have an additional ground rod close to the antenna for a little extra safety. The antenna ground can 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 Drip Loop allows rain to collect and fall (drip) off the bottom of the loop instead of collecting at the conduit into the home.
RF CHANNEL FREQUENCIES
Each RF channel is 6 MHz wide.
|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|
The Best of the Essentials
DTV Antennas and Accessories
Outdoor Antennas -- Indoor Antennas -- Amplifiers -- Signal Splitters -- Coax -- Installation Hardware