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hambasics:sections:mathbasics [2025/06/25 21:28] – va7fihambasics:sections:mathbasics [2026/04/01 21:33] (current) – [Conversion] va7fi
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 A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit. A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit.
  
-In the previous section, we saw that Mhz means a million Hertz.  Here's a list of the most common ones:+In the previous section, we saw that MHz means a million Hertz.  Here's a list of the most common ones:
  
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 ===== dBm ===== ===== dBm =====
  
-A related measurement is the dBm.  While the decibel (dB) is a ratio between two quantities (saying "20 dB" is the same as saying "100 times more"), the dBm is a ratio between one quantity and 1 mW.  That is, it's a measures of how much stronger (or weaker) the power of something is compared to 1 milliwatt.+A related measurement is the dBm.  While the decibel (dB) is a ratio between two quantities (saying "20 dB" is the same as saying "100 times more"), the dBm is a ratio between one quantity and 1 mW.  That is, it's a measure of how much stronger (or weaker) the power of something is compared to 1 milliwatt.
  
-For example, a typical fibre optic light signal to a house for internet has a light level of -16 dBm.  Before we go through the math, recall that 16 dB = 10 dB + 3 dB + 3 dB.  Which means, the ratio is 10 × 2 × 2 = 40.  Let's now see why -16 dBm is equal to a power of 25 μW (microwatts):+For example, a typical fibre optic light signal to a house for internet has a light level of -16 dBm.  Before we go through the math, recall that \$16 \text{ dB} = 10 \text{ dB} + 3 \text{ dB} + 3 \text{ dB}\$.  Which means, the ratio is \$10 \times 2 \times 2 = 40\$.  Let's now see why -16 dBm is equal to a power of 25 μW (microwatts):
 <WRAP centeralign> <WRAP centeralign>
 \$$-16 \text{ dBm} = 1 \text{ mW} \div 10^{1.6}  \approx 1 \text{ mW} \div 40 = 0.025 \text{ mW} = 25~\mu \text{W} \$$ \$$-16 \text{ dBm} = 1 \text{ mW} \div 10^{1.6}  \approx 1 \text{ mW} \div 40 = 0.025 \text{ mW} = 25~\mu \text{W} \$$
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 |  ...                                     ||| |  ...                                     |||
 ^     4095 ^          FFF ^   1111 1111 1111 | ^     4095 ^          FFF ^   1111 1111 1111 |
-|     4096 |         1000 | 1 0000 0000 0000 |+|     4096 |         1000 |  1 0000 0000 0000 |
  
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hambasics/sections/mathbasics.1750912139.txt.gz · Last modified: by va7fi