How to convert dBm to W/m²?

Unit conversion and RF calculations

How to convert dBm to W/m²?

Postby Moderator » Friday 10. September 2010, 19:11

The formula to convert dBm to W/m² is:

S
[W/m²] = (10^(p[dBm]-G[dBi]) / 1000) * ((4 * Pi) / (Lambda[m]²))

Remarks:
G = Antennagain
Lambda = Wavelength
Pi = 3,1415

Example:
Say your have a reading of -40dBm at 950MHz with a HyperLOG 7025 antenna (which offers a gain of 4,9dBi at 950MHz). The result is:
0,000.004.08W/m² or 4,08µW/m²
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Re: How to convert dBm to W/m²?

Postby javholgu » Friday 5. August 2011, 07:08

Hello,
I am Javier. I am interested on citing the source of this formula (page 63 of manual) in an article and would like to ask if you know a solid reference to use. Also I would appreciate if you could share a mistaken formula and its reliable source to convert dBm to W/square meter where frequency is not considered.
I would appreciate your valuable feedback
Regards,
Javier
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Re: How to convert dBm to W/m²?

Postby Moderator » Friday 5. August 2011, 07:24

This is standard math and physics.
The formula clearly shows that its IMPOSSIBLE to convert dBm to W/m² WITHOUT adding the frequency.
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Re: How to convert dBm to W/m²?

Postby Twitch » Monday 20. June 2016, 06:27

I have a hyperlog 6080 what is the antennae gain and where do I find the lambda number for the formula?
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Re: How to convert dBm to W/m²?

Postby Twitch » Monday 20. June 2016, 06:31

Where do you get the dBi number?
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Re: How to convert dBm to W/m²?

Postby Twitch » Monday 20. June 2016, 06:33

where do you get the dBi number?
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Re: How to convert dBm to W/m²?

Postby Twitch » Monday 20. June 2016, 06:53

The W/m2 numbers, I don't understand why the , comes before a decimal point. For example 0,00.004.08W/m2 what does the comma and decimal point mean in comparison with american numbers.
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Re: How to convert dBm to W/m²?

Postby Moderator » Monday 20. June 2016, 07:13

This are the international physical ISO standards used by most of the world. The US simply do it "wrong".
Have a look at https://en.wikipedia.org/wiki/Decimal_mark
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