Volt/meter to Decibel: Understanding Attenuation Loss from 112dB to -36dB

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Discussion Overview

The discussion revolves around interpreting attenuation loss in decibels (dB) for electric field measurements referenced to 1 volt/meter, with values ranging from 112 dB to -36 dB. Participants explore the mathematical relationships and physical implications of these values, questioning the validity of the reference point and the context of the data.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks to understand the interpretation of attenuation loss in a table of dB values referenced to 1 volt/meter.
  • Another participant suggests a formula for converting voltage ratios to dB, indicating a change of a factor of two corresponds to approximately 6.02 dB.
  • A participant questions the high value of 112 dB, proposing that the reference might actually be 1 microvolt/meter instead of 1 volt/meter.
  • A different participant asserts confidence in the 1 volt/meter reference and expresses confusion regarding the values.
  • One participant raises concerns about the context of the table, suggesting that if it relates to a physical situation, the values seem excessively high.
  • Another participant claims to have researched and concluded that 1V/m corresponds to 0 dBμV/m, interpreting the values in the table as conversions from this reference, and calculates an attenuation of 8 dB for a value of 112 dB.
  • One participant challenges the definition of dB used, stating that 1V/m is 0 dBV/m and 120 dBμV/m, emphasizing that dB is a logarithmic measure of power ratio and assumes the same impedance.

Areas of Agreement / Disagreement

Participants express differing views on the reference point for the dB values, with some asserting confidence in the 1 volt/meter reference while others propose alternative references. The discussion remains unresolved regarding the interpretation of the high dB values and the correct application of the dB definitions.

Contextual Notes

There are unresolved assumptions regarding the context of the table and the physical situation it represents. The discussion highlights potential confusion over the definitions and conversions related to dB measurements.

Ionito
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I have a table containing the magnitude (dB) of an electric field referred to 1 volt/meter.
The values range from 112 to -36dB. How can I properly interpret the attenuation loss in each case in this table? In other words, for a reference of 1 volt/meter and no signal loss, what is the expect value in dB?
 
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dB = 20Log(V2/V1), or

V2/V1 = 10^(dB/20)

A change of a factor of two is

20Log(2) = 6.02 dB

Bob S
 
If the reference is 1 volt/meter then one would expect that to be equal to 0 dB. However 112 dB referenced to 1 volt/meter seems unreasonably high. Are you sure the reference wasn't to 1 microvolt/meter?
 
Hi skeptic2, completely sure about 1V/m, that is why I did not understand.
 
What is the context of the table?
If it is simply tabulating a mathematical relationship there need be no problem. If it it supposed to relate to some physical situation then it seems to have some rather high values: nearly 0.5 MV/m! Hardly a "signal" strength!
 
I made some research and figure out the following: 1V/m= 0 dB[tex]\mu[/tex]V/m.
Therefore, the values I am seeing in the table correspond conversions of this reference. If the signal is not attenuated, I have 1V=1*106*[tex]\mu[/tex]V and 20log(V2/V1) in this case is 120. A value of 112dB means that the attenuation is 8dB. I believe this is the explanation.
 
But that definition of the dB is not right.
1V/m is 0dBV/m
or
1V/m is 120dBmuV/m
That's an identity, surely.

That assumes the same impedance. dB is actually a log of power ratio.
 

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