Wireless: dB gain / loss chart for UHF wireless systems
Question: How much loss can a UHF wireless system handle using a passive splitter or combiner? We are thinking
of combining multiple WBS-670/680 systems together to reduce the number of antennas in our workspace.
Answer: Multiple 3rd party vendors make passive and active splitters, combiners and antennas for UHF wireless systems.
Signal loss and or gain can make or break the effectiveness of a combined antenna systems for transmit and receiver antennas,
see the chart below for a guide as to how much loss a system can tolerate.
Other factors to look out for:
Transmit antennas - FCC power limit regulations, intermod of the combined frequencies, RF power input limits on the selected
combiner used to combine transmit antenna signals and any bandwidth filtering and or frequency range limitations, RF loss of
coaxial cable used to make connections.
Receive antennas - loss per port of a passive splitter selected, loss of coaxial cable used to make connections, passive or active
gain of selected antenna, bandwidth of selected splitter.
This table is designed to help you visualize what changes in dB signal level does in a RF system. The dB change listed
above can be reflected as either loss between the radio/transmitter and the antenna, or gain in amplification and antenna.
System Gains
Every 1dB of gain raises your output power 20%, where 3dB doubles output power.
Antenna gain is a function of size, no matter what design it is. A small antenna that claims unreasonably high gain will not
perform as you expect it to.
System Losses
Every 1dB of loss in the system represent a full 20% -loss- of power. Just as in gain, 3dB of loss represents a loss
of 50% of your power.
LMR400 has 6.6dB per 100ft, so keep your runs as short as possible.
All losses are cumulative, so every element of your system has to be accounted for.
As you can see, even the smallest change makes a radical difference.
Keep this table in mind when selecting the grade of cable and other items
(passive and active splitters, combiners and antennas) in the system you are building.
of combining multiple WBS-670/680 systems together to reduce the number of antennas in our workspace.
Answer: Multiple 3rd party vendors make passive and active splitters, combiners and antennas for UHF wireless systems.
Signal loss and or gain can make or break the effectiveness of a combined antenna systems for transmit and receiver antennas,
see the chart below for a guide as to how much loss a system can tolerate.
Other factors to look out for:
Transmit antennas - FCC power limit regulations, intermod of the combined frequencies, RF power input limits on the selected
combiner used to combine transmit antenna signals and any bandwidth filtering and or frequency range limitations, RF loss of
coaxial cable used to make connections.
Receive antennas - loss per port of a passive splitter selected, loss of coaxial cable used to make connections, passive or active
gain of selected antenna, bandwidth of selected splitter.
This table is designed to help you visualize what changes in dB signal level does in a RF system. The dB change listed
above can be reflected as either loss between the radio/transmitter and the antenna, or gain in amplification and antenna.
System Gains
Every 1dB of gain raises your output power 20%, where 3dB doubles output power.
Antenna gain is a function of size, no matter what design it is. A small antenna that claims unreasonably high gain will not
perform as you expect it to.
System Losses
Every 1dB of loss in the system represent a full 20% -loss- of power. Just as in gain, 3dB of loss represents a loss
of 50% of your power.
LMR400 has 6.6dB per 100ft, so keep your runs as short as possible.
All losses are cumulative, so every element of your system has to be accounted for.
As you can see, even the smallest change makes a radical difference.
Keep this table in mind when selecting the grade of cable and other items
(passive and active splitters, combiners and antennas) in the system you are building.
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