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 3. GQ EMF EF Meter RF Spectrum Power Analyzer
 What is dBm?
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Mugless

Australia
11 Posts

Posted - 06/20/2020 :  20:11:07  Show Profile  Reply with Quote
Hi Everyone,

Please explain the definition GQ 390 uses for dBm.

I assume the equation of dBm is:
dBm = 10 * Log10 (P_reading) / (P_reference)

If this is correct, please confirm that P_reference = 100,000 mW/m2, or 10 mW/cm2, since 0 dBm corresponds to that number:



Thanks,
Doug
Reply #1

EmfDev

1461 Posts

Posted - 06/22/2020 :  09:50:32  Show Profile  Reply with Quote
The RF power reference is 1mW. It is converted to density with other parameters including gain.
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Reply #2

Mugless

Australia
11 Posts

Posted - 06/22/2020 :  16:00:28  Show Profile  Reply with Quote
Thanks,

So the conversion to 1 mW to power density involves a factor of 100,000 that takes into account other parameters including gain.
Is that the gain of the built-in antenna?
What are the other parameters?
Is the 100,000 factor derived from calibration of the GQ 390 against standard, reference equipment? If so, the fact that it is such a neat, round number is odd, if not even suspicious!!
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Reply #3

EmfDev

1461 Posts

Posted - 06/23/2020 :  10:03:17  Show Profile  Reply with Quote
0dBm converts to 1mW but in power density becomes 10mW/cm2. 10mW/cm2 converts to 10^5 mW/m2.
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