Digital TV Reception Factors Tower Locator Antennas Amplifiers Cables Installation Frequency Networks

OTA DTv TV Coax Cables, Splitters, and Connectors

PAGE CONTENTS -- Cables | Splitters | Connectors | Adapters/Baluns | Loss Calculator | Signal Power

Twin-lead and coax CABLES
RG-6 coax (75 ohm) cables with F-type male connectors should be used to connect the antenna to all televisions and devices. RG-6 is available with 2, 3, or 4 layers of shielding. Four layers has better immunity from interference, is more sturdy and durable (and expensive), but is less flexible than two layers. Quad shielded, 4 layers, should be used for outside cables.

RG-59 coax cable can be used, but it is a little more lossy and has only a single layer of shielding. Twin-lead (300 ohm) cable, sometimes called ribbon cable, is very lossy for UHF channels and should be replaced (with RG-6). RG-11 cable is designed for transmitting (higher power) over long cable runs, has less loss, is bigger and heavier, available with dual or quad shielding, and the most expensive.

Cable(1) ohms(2) Shielding Use
RG-6 75 2 - 4 Layers TV signals
RG-59 75 1 Layer Lower Frequency, Video
RG-11 75 2 or 4 Layers High Power, Low Loss
Twin-Lead 300 none VHF and lower

(1) RG stands for "Radio Guide", and is widely used to describe cable performance. RG designations were developed by the military during World War II. The military has replaced the radio guide reference with military specification MIL-C-17.
(2) Ohms is cable impedance, the ratio of the electric to magnetic field.

CABLE LOSS
The longer the cable the greater the signal loss. Loss also depends on frequency, the higher the frequency (the higher the RF channel), the greater the loss. RF channels in the VHF band have less loss than channels in the UHF band. Cable (signal) loss is measured in power decibels (dB), and is the power ratio (out/in) on a logarithmic (dB) scale.

cable loss

Decibels Converter (Show / Hide...)

Cable Loss Calculator
Cable Type:
RF Band or Channel:
Cable Length(s):

Cable Loss in decibels (dB)


Coax Cables (75 ohm)
cable
Antenna & Accessories Store

Note, loss calculations are for high quality cables. Cheaper cables may have greater loss, and may not weather well. Some higher quality cables may have less loss. Differences can be as great as plus or minus several dB per 100 feet.

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SIGNAL SPLITTERS
A signal splitter / combiner is used to connect to multiple TV's and devices. Splitting the signal to 2 output ports delivers a little less than half the signal to each output. Signals at the outports are reduced by -4 dB, equivalent to adding about 70 feet of cable. The more outport ports, the greater the signal loss. Keep the number of signal splitters to a minimum.

Signal Splitter Loss - -
Output
Ports
Loss
per Port
2 -4 dB
3 -6 dB
4 -8 dB
8 -12 dB

Splitter and wall output ports that are not used should be terminated with a 75 ohm load or terminator.

Signal
Splitter /
Combiner

Splitter
Antenna &
Accessories
Store
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CONNECTORS
Barrel Connector Male-to-Male Connector Male-to-Female Connector Cables and most televisions and antennas use F-type connectors, male connectors on the cable, and female connectors on the antenna and television. Two cables can be connected using an F-type female-to-female, also called barrel, cable connector. Wall jacks and coax ground blocks usually have barrel connectors. Cable connectors introduce a small signal loss, typically about -0.5 dB.

ADAPTERS / BALUNS
Older antennas and TV's use a 300 ohm twin-lead connection, in these cases a coax-to-twin-lead adapter (75/300 ohm) is required. The adapter is a matching network (discrete and/or strip-line resistors, capacitors, inductors) or a balun (matching ferrite transformer). An adapter works both ways (bi-directional), signals go from coax to twin-lead or twin-lead to coax. Adapter

300 / 75 OHM ADAPTER LOSS
-0.2 dB for channel 2
-1 dB for channel 14
-2 dB for channel 69

Connectors & Adapters
connectors
Antenna & Accessories Store
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SYSTEM LOSS CALCULATOR

Estimate signal loss for the TV (outlet or outlets) with the most splitters and longest cables to the antenna. Trace the signal from the antenna to the TV, noting cable length, and the number and type of signal splitters, and the number of connectors and adapters.

Antenna-to-TV Signal Loss
Cable Type:
RF Band or Channel
Cable Lengths(s):
Signal Splitters: 2 Ports , 3 Ports
4 Ports , 8 Ports
Connectors:
Adapters: 300 / 75 ohm

Cable Loss (dB)
Splitters Loss (dB)
Connector Loss (dB)
Adapter Loss (dB)


TOTAL LOSS (dB)


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SIGNAL POWER
Signal power in dBm drops directly by power decibels (dB) loss. The power unit "dBm" is decibels above or below one milliwatt (1 mW).

Pout = Pin - dB
Pout - signal power (dBm) out of cable.
Pin - signal power (dBm) into cable.

A negative dBm is dB's below a milliwatt, a positive dBm is dB's above a milliwatt, 0 dBm = 1 mW. Television broadcast signals are typically between 10 kW (70 dBm) to 1000 kW (90 dBm). Receive signals are between -5 dBm (316 µW) to -65 dBm (0.0003 µW).

dBm = 10 log10 (mW)
mW = 10(dBm/10)

dBm

dBm
to watts

watts
to dBm


dBm - decibels above or below 1 mW
µW - microwatts = 0.000 001 W
mW - milliwatts = 0.001 W
W - watts = 1 W
kW - kilowatts = 1000 W

Digital TV Reception Factors Tower Locator Antennas Amplifiers Cables Installation Frequency Networks

TV Coax Cables, Splitters, and Connectors
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