Decibels - Revision history

TimVK4YEH: fixed spelling error

2009-11-16T20:45:50Z

fixed spelling error

← Older revision		Revision as of 13:45, 16 November 2009
Line 38:		Line 38:
	Reference levels were created because dB is a unitless calculation, unlike calculations such as [[Voltage \| voltage]], power [[Current \|current]] etc.		Reference levels were created because dB is a unitless calculation, unlike calculations such as [[Voltage \| voltage]], power [[Current \|current]] etc.

	In Ham radio, the most common measurements that requires the use of dB are [[Gain]] and [[Radiated Power Measurement]]. Further information about ~~refeence leves~~ can be found in the linked pages.		In Ham radio, the most common measurements that requires the use of dB are [[Gain]] and [[Radiated Power Measurement]]. Further information about reference levels can be found in the linked pages.


	{{electronics}}		{{electronics}}

Carlb: /* What is a reference level? */

2009-04-09T01:27:12Z

What is a reference level?

← Older revision		Revision as of 18:27, 8 April 2009
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	In Ham radio, the most common measurements that requires the use of dB are [[Gain]] and [[Radiated Power Measurement]]. Further information about refeence leves can be found in the linked pages.		In Ham radio, the most common measurements that requires the use of dB are [[Gain]] and [[Radiated Power Measurement]]. Further information about refeence leves can be found in the linked pages.


			{{electronics}}

TimVK4YEH: New page: Related wiki pages Gain, Radiated Power Measurement ==What is a decibel dB?== '''Some facts''' * a decibel is the ratio of two power measurements * decibels is a logarithmic rel...

2009-04-04T23:16:19Z

New page: Related wiki pages Gain, Radiated Power Measurement ==What is a decibel dB?== '''Some facts''' * a decibel is the ratio of two power measurements * decibels is a logarithmic rel...

New page

Related wiki pages [[Gain]], [[Radiated Power Measurement]]

==What is a decibel dB?==

'''Some facts'''

* a decibel is the ratio of two power measurements
* decibels is a logarithmic relationship
* a decibel is 1/10 of a Bel
* decibels have no units
* decibels were created to make sense of the relationships between numbers that are several orders of magnitude different in size. eg 32 000 000 000 000W and 450W
* the formula used to calculate decibels is:

Power difference in dB = <math>10 \log_{10}\frac{P_A}{P_B}</math>

==Why use decibels==

Using the two numbers above:

<math> P_A = 32 000 000 000 000</math>W and <math> P_B = 450</math>W , then:

<math>10 \log_{10}\frac{32000000000000}{450}</math> <math>\approx</math> 109

Hence we would say that Power A is approximately 109dB greater than Power B

==What about voltage comparisons in dB?==

the relationship between Power and Voltage is:

<math> Power = \frac{Voltage^2}{Resistance} </math>

Squaring a number will double its logarithm (log), so

Power difference in dB = <math>20 \log_{10}\frac{V_A}{V_B}</math>

==What is a reference level?==

Reference levels were created because dB is a unitless calculation, unlike calculations such as [[Voltage | voltage]], power [[Current |current]] etc.

In Ham radio, the most common measurements that requires the use of dB are [[Gain]] and [[Radiated Power Measurement]]. Further information about refeence leves can be found in the linked pages.