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 3. GQ EMF EF Meter RF Spectrum Power Analyzer
 390 transmitting on 428mhz?!
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United Kingdom
8 Posts

Posted - 07/12/2020 :  06:47:35  Show Profile  Reply with Quote
Hi again, my replacement EMF390 unit works as expected (ie no settings amnesia) with one rather peculiar bug;

I searched throughout the house for a signal spike on 428.020mhz only to find it coming from the EMF390 .

Is that normal? Does anyone else know why the EMF390 transmits a signal powerful enough to be picked up on my UV5R from nearly 800 meters away?

It must affect the RF readings quite abit!


Edited by - fendiag on 07/12/2020 06:55:06
Reply #1


44 Posts

Posted - 07/12/2020 :  20:54:24  Show Profile  Reply with Quote
That is very interesting. Are you using USB to power the unit? I've found that, if I plug mine into a USB port on my power strip, that I get so much rf hash coming in that the rf browser is useless. This doesn't happen on batter power. Do you pick up an audible sound on your radio. Maybe it's related to the clock frequency of the microprocessor, but I don't know.


Ron Frazier - In training with the Building Biology Institute ( to become an independent Electromagnetic Radiation Specialist (EMRS). We measure, document, analyze, and recommend mitigations for harmful EMF exposures.
All my statements are mine alone though.
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Reply #2


United Kingdom
8 Posts

Posted - 07/13/2020 :  07:43:21  Show Profile  Reply with Quote
Hi Rfrasier, sure do, a beacon like sound, i admit that it required a directional antenna to pick up out to 800m, but still supprised that there was no null built in to at least compensate for the self noise.

So I had a closer look at the unit and it does indeed transmit roughly 5/6mw on 428.020mhz with very few transients. The signal is strongest on the right vent.

just wondered if this is a defective(grossly inaccurate)unit or not.

Cheers again,
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Reply #3


United Kingdom
8 Posts

Posted - 07/13/2020 :  08:23:28  Show Profile  Reply with Quote

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Reply #4


1868 Posts

Posted - 07/13/2020 :  10:22:58  Show Profile  Reply with Quote
We investigated and found that this weak noise signal is coming from the unit. We are still trying to find out where it comes from. Maybe you can test it with you radio by testing the LCD backlight, or when you are in RF browser (suppose that the RF spectrum is off in this mode), does it still pick up the signal.
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Reply #5


United Kingdom
8 Posts

Posted - 07/15/2020 :  08:23:17  Show Profile  Reply with Quote
I'd rather not dissasemble the meter as I am about to return it.

My guess after a bit of 'google-fu'. Is that is the graphics shader clock? I would try isolating that circuit and test it with an oscilloscope. Hand-held frequency counters have compartmentalised circuits covered with Mu foil.

Way beyond my comfort zone

I'd love to know where the signal is comming from.
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