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A decibel (dB) is a unit of measurement relative to voltage that tells us how much signal strength is in an RF signal. The more dB that are measured, the stronger and better the signal. Since dB is measured on a logarithmic scale, the voltage doubles with every additional 6 dB of signal.

In the case of TV field strengths, we effectively measure the voltage across 1 meter of space. The designation "uV" stands for microvolt, which is one millionth of a volt, so 1 uV/m indicates a voltage of one millionth of a volt when measured across 1 meter of space.

The term "6 dB relative to 1 uV/m" (written as 6 dBuV/m) means 2 uV/m, while 12 dBuV/m would be 4 uV/m. The reason we use the dB ratio is to make the figures easier to handle when you have larger signals. For example, 1,000 uV/m is 60 dBuV/m, and 1,000,000 uV/m is 120 dBuV/m. It's also very useful when estimating aerial sizes.—JB