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 3. GQ EMF EF Meter RF Spectrum Power Analyzer
 Signal Symbols images and negative dBm
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Japan21

Australia
5 Posts

Posted - 10/22/2021 :  03:31:11  Show Profile  Reply with Quote
Hi Fellow 390users, (sorry long post)

Just got my EMF390, nice little gadget. Quick 2 day from AmazonAu. I need some help identifying the signal symbols that I am receiving, screen shots taken from the analyzer. Can anyone help identify the following images as Wifi, microwave, radar, laser, cell tower.... I do not have any clue what any of these signals mean. (newbie)

2) Can anyone also help me with the dBm, are the values in the images okay. Whats a dangerous dbm that i should be looking out for? What does a negative dbm mean?

3) Are any of these signals exceeding the Australian RF limit of 10 W/m2 ? or 4 watt radiated power for devices 2ghz.

4) Does the shading inside the symbol mean anything? more eme energy??? When there is signal shading my eyes hurt a bit.

>>The spectrum allocation ends at 2.484 (so why is there a signal at 2.488, 2.501, 2.496 ..) what devices use these frequencies?

These signals from from neighboring apartment (below/next) turned off all my gadgets except microwave. Most of these queries would be super simple for lots of you, but I have no clue so Thanks all for your help!And greetings from Australia.




Cheers, Nelly

Edited by - Japan21 on 10/24/2021 23:53:56
Reply #1

Damien68

France
545 Posts

Posted - 10/25/2021 :  00:39:46  Show Profile  Reply with Quote
dBm is a logarithmic transformation applied to a power level with a reference at 1mW.
you can googling "dBm definition" to learn more.
In summary:
0 dBm = 1mW
if dBm> 0: the measured power is greater than 1mW
if dBm <0: the measured power is less than 1mW

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 10/25/2021 00:40:10
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Reply #2

Damien68

France
545 Posts

Posted - 10/25/2021 :  00:56:09  Show Profile  Reply with Quote
2.484 is the center frequency of the last wifi b/g/n chanel (chanel 14), but around this central frequency there is the modulation band.
in fact the Wifi b/g/n channel 14 occupies the entire following frequency spectrum : 2473 to 2495 MHz

Mastery is acquired by studying, with it everything becomes simple
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Reply #3

Japan21

Australia
5 Posts

Posted - 10/25/2021 :  19:17:12  Show Profile  Reply with Quote
Thanks Damien for the reply, i googled dbm but got lost in the technical.

lets take one screen shot and walk through it, like i said i really do not have any idea about this, so treat me like a you would
someone that only knows to 'turn on and off a computer'. not tech savvy at all stuff you think is basic is hard even when i google.

Anyway say first screen shot we've got 3 dbm -74, -84Ave and -64 what does all these mean?

What does the shading inside the symbol mean?

please help i an completely lost



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Reply #4

Damien68

France
545 Posts

Posted - 10/25/2021 :  23:52:04  Show Profile  Reply with Quote
Hi Japan21
This is a conversion table:

pW= pico Watt, nW = nano Watt, uW = micro Watt, mW = milli Watt.

conversion formula:

extract of:
https://www.rapidtables.com/electric/dBm.html
(be careful with their online dBm calculator it does not work very well).

So -70 dBm = 100 pico Watt
and -74 dBm is around 40 pico Watt (it is the power received by the EMF-390 embeded antenna).

I don't know exactly what is the shading inside the symbol I don'y have EMF-390 (I have to buy one), but It must be the spectrum read and the fine line must be either the peaks or the maximums with an afterglow.

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 10/26/2021 00:05:25
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Reply #5

Japan21

Australia
5 Posts

Posted - 10/26/2021 :  19:38:03  Show Profile  Reply with Quote
Thanks damien68.

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Reply #6

Japan21

Australia
5 Posts

Posted - 10/27/2021 :  02:38:10  Show Profile  Reply with Quote

Hi emfdev

Can you help me with the signal identification in the picture.
From the 390meter booklet am not able to identify any of these signal symbols.
Am assuming photos 7, 8, 11, 15 are pulsed energy???

Not sure what the others are. Which one is microwave? so on...

Also the shading inside the symbol what does that mean? thanks for your help.

Nelly
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Reply #7

EmfDev

1483 Posts

Posted - 10/27/2021 :  09:46:52  Show Profile  Reply with Quote
Hi Japan21,

A bell shape signal that that ranges around 200mHz coming from a WiFi router. I can see at least 2 hot spots. I think the closer one is the 2.446GHz and the other one is around 2.430GHz. Photo 8 shows a 2.481 GHz which may come from a bluetooth device. A microwave signal also looks like that and moves left to right and vice versa but it usually lasts until the microwave oven is off.

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Reply #8

Japan21

Australia
5 Posts

Posted - 10/29/2021 :  00:22:57  Show Profile  Reply with Quote
Cheers
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