Losses and Gains per dB
Percentage of lost or gained signal per dB of change
|% Diff||dB Diff||% Diff||dB Diff||dB Diff||% Diff|
|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. Let's break these two down: |
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. All of the antennas we stock have been tested on a Anritsu antenna analyzer to verify the manufactures rating.
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... Pigtails, coax runs, lightning protectors, etc all have to be added up to get the full view of overall loss.
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 in the system you are building. You can also use our dB to Watt Table to help keep your system in check with FCC regulations regarding power output. If you have more questions or concerns, just contact us, we're more than happy to help.