Cornet ED88TPlus Electrosmog Meter, Scam or naive application note design?

[OZ1LQO]

I came across the ED88Tplus which apparently is quite popular in the 'EMF-Aware' community.
I don't take part in any of this myself, but as an RF and Antenna engineer since 25y, I decided to crack it open.

I was surely in for a treat 

As the subject line says, I'm divided between this being a deliberate scam, or just a naive design, maybe a combo.
It remains a fact that people pay $200 for 'instruments' like this. They trust them and use them as their reference in the ongoing debate.
And learning how they built it, I felt so professionally insulted that I just had to show this to others 

Enjoy - and if you happen to be the happy owner of one of the other 'electrosmog' meters out there - then crack it open and show it to us! 

Now I'll go scan for bugs and ghosts.. 

[AVGresponding]

Kind of a scam in some ways, as they seem to be marketed at people with little understanding of physics, or science in general.

I've seen yt vids where people hold emf detectors close to their electric meters, and declare in conspiratorial tones "look at how much radiation is coming off this!".

 

[Cyberdragon]

Pffff...that one is fancy (still has a 324 in it somewhere though), all digital shmigital.

I tore down an analog one before (an early "cellphone radiation" meter), and there was just two LM324s (one for RF, and one for the magnetic field probe) and a germanium diode RF detector. Yes, they still make analog ones, I'm sure the circuits are still similar between models.

[Perene]

I made a few recordings years ago with the Cornet and uploaded here:

https://www.youtube.com/playlist?list=PLCAm_SFVMXIIHaGnqLV-axtFgrjic7ozG

I am a total noob when it comes to EMF meters, so I need to ask a few questions... I have the ED88T, the 2015 Acoustimeter and the UHS2 (for magnetic fields only).

- If I hold any of these meters close to the source of the EMF then the numbers read by them are useless? if that's the case then how far should we point any of these meters for accurate readings?

- Why the Cornet and Acoustimeter are useless for measuring 5 Ghz wi-fi signals? I did this test: disabled the 2.4 Ghz signal from my router and only let 5 Ghz with the lowest transmit power possible (2.4 GHz when turned on it's the same). I could only make these EMF meters to go up when I put them right in the front of the router, say, at no more than 6 ft / 2 meters or less. Even so the increase was insignificant.

When I did the same test with 2.4 Ghz (and 5 GHz disabled) the EMF levels increased significantly even at higher distances. It is well known 2.4 GHz can permeate your house far more than 5 Ghz, 2.4 is always stronger, so a difference would be expected.

But what is not normal is this (nevermind about the numbers):

2.4 GHz enabled:
- At 15-20 ft either AM and Cornet measure, say, 2 V/M (let's assume they register this)

5 GHz enabled:

- At 15-20 barely reaches 0.5 V/M. It's like the signal isn't even there.

I have no idea if this has been fixed over the years or how this SAFE AND SOUND PRO would measure. This needs some clarification because even the GIGAHERTZ SOLUTIONS meters, which are more expensive and aimed for professionals, don't have any EMF meter that can cover so much.

They sell the HFW35C RF Meter which covers the frequency range of 2.4 GHz to 6 GHz.

The HF35C range is 800 MHz to 2.7 GHz.

Acoustimeter = 200 MHz - 8 GHz
Cornet = 100 MHz - 8 GHz

How is this possible?

[dmills]

Basically ANY instrument claiming that frequency range with an internal antenna that isn't a few feet across is highly suspect.

RF types use calibrated spectrum analysers with calibrated antennas (That are usually not all THAT broadband, we usually own several) to make field strength measurements in the far field, and a separate set of E and H field probes for near field work (Where the two fields are best viewed separately).

While you could, maybe, produce a calibration curve for those meters, that told you how many dB to add or subtract from the the reading as a function of frequency, it is also dependent on orientation, and even what else is in the vicinity (Like say the big bag of mostly water holding the thing).

The ED88T (Taking that teardown as gospel) has a 75mm dipole internally, that will be a mess of different sensitivities in different directions by 5GHz and as the instrument has no compensation for frequency...

Any RF engineer is going to consider all of these instruments to be a joke for anything except strictly comparative measurements at a single frequency, and even then I would be trying to find something better.

For the real deal, Keysight/Rhode & Schwartz/Anritsu/Cobham...
All have gear that is actually reliable for this, but a decent spectrum analyser is well over a grand, and needs someone skilled in its use to get good data.

For the cheap way, a HackRF1 or such and a laptop, plus a broadband noise source so you can calibrate the thing and some calibrated antennas for the bands of interest.

[TimFox]

Years ago, scam artists, to sell aluminum siding to house owners, would wave a normal photographer's light meter about, showing the alarming swings of the meter as it went past the front window, claiming it showed heat loss.  But it wasn't digital, was it?