| Author |
 Topic  |
|
|
Yves16
France
8 Posts |
 Posted - 03/02/2024 : 08:47:41
|
Hello from France,
Here are spectrums for 380-480 Mhz band, my spectrum is from SDR radio with an mini airspy and wide band antenna. The EMF 390 is very creative in signals but do not seem to be a measure instrument on this band, on FM brodcast band also, i have a 10 Kw FM antenna at 400 meters and a lot of measures have been made from my home by technicians and me (technician also) they indicates about 2 to 3 V/m or 1 to 2.5 micro-Watts/cm2; the EMF 390 indicates 0.01 micro-Watts/cm2 in RF mode and fabulous 80 V/m in EF mode.
Very different spectrums
In Wifi and phone frequencies mode, measures seems to be OK.
Cheers
Yves |
Edited by - Yves16 on 03/02/2024 08:50:20
|
|
| Reply #1
EmfDev
2150 Posts |
Posted - 03/05/2024 : 10:04:38
|
| Hi Yves, which EF mode did you use to measure the RF? And also what exact frequency are you referring to? |
 |
|
| Reply #2
Yves16
France
8 Posts |
Posted - 03/06/2024 : 04:31:02
|
Hello,
I am in 387-464 Mhz RF Spectrum and like Ceki, i have always the same spectrum with lot of noise, everywhere. The image on bottom is from Airspy mini in spectrum analyser at the same place than the EMF 390 for comparaison.
For FM i was mesuring in all in one mode and vertical mode.
The EMF indicates also in spectrum analyser -77dbm average in 387-464 Mhz and -93dbm average in 76-108Mhz.
The two mesures with airspy mini are made with same gain, and there is seemly nothing in 387-464 Mhz and, because we have a 10 Kw FM emitter at 400 meters, huge signals (mesured 2.5 V/m with professional material on same place).
So my EMF 390 see signal that don't exist on 387-464 Mhz and see a little signal on 76-108Mhz.
I receive the 2 march 2024 the EMF 390V2, revision 3.74.
|
Edited by - Yves16 on 03/06/2024 04:35:52 |
|
|
| Reply #3
EmfDev
2150 Posts |
Posted - 03/06/2024 : 14:47:56
|
| the ambient RF seems similar but are you able to check if the signal on the 90MHz is real? |
|
|
| Reply #4
Yves16
France
8 Posts |
Posted - 03/07/2024 : 04:21:59
|
Hello,
The first problem is on 380-480 Mhz, the EMF390 see huge signals that don't exist (-77dbm average), compare with the airspy vue.
The second problem is the level indicated for 76-108 Mhz , - 93 dbm average is low signal, the signal is much more important.
The EMF see huge signal in 380-480 Mhz and little signal in 76-108 Mhz, it is the opposite of reality.
The EMF390 see the same huge signal in 380-480 Mhz everywhere, also in campain at 10 km from home.
Yves |
Edited by - Yves16 on 03/07/2024 04:26:29 |
|
|
| Reply #5
em535
4 Posts |
Posted - 03/10/2024 : 05:25:13
|
My 380-480 spectrum looks almost the same:
first pass 76-108
second pass 76-108
 |
|
|
| Reply #6
Yves16
France
8 Posts |
Posted - 03/11/2024 : 10:04:58
|
Thanks em535. I have the EMF390v2 revision 3.74 received a week ago.
Do you have also a recent V2 model.
It seems to indicate same signal everywhere to everybody on 380-480 Mhz, so the mesure in V/m and micro-W/cm2 or m2 are also false for frequencies from 50 Mhz to 1 Ghz.
For me it is a problem because i want to mesure frequencies below 800 Mhz. |
Edited by - Yves16 on 03/11/2024 10:08:49 |
|
|
| Reply #7
EmfDev
2150 Posts |
Posted - 03/11/2024 : 11:39:26
|
| First of all, the 10MHz to 10GHz reading from RF Browser uses a different sensor and antenna. The 2.4GHz-2.5GHz in RF Spectrum also uses different chip and antenna. The 300-928 MHz on RF spectrum also uses different chip and antenna. And lastly, the 50MHz-108MHz uses different chip and antenna. That may explain the reason why the 76-108 is varied differently with 380-480. But based on your picture of the airspy vue, it is not very sensitive and the lowest is -75 dbm which means it cannot detect lower than that. |
|
|
| Reply #8
em535
4 Posts |
Posted - 03/12/2024 : 04:05:04
|
| Yves16, it's also a 390v2 rev 3.74 I bought a few weeks ago. |
|
|
| Reply #9
Yves16
France
8 Posts |
Posted - 03/13/2024 : 03:26:09
|
@ em535
Thanks, i know that a chip used in EMF390 V1 did diseapear and V2 have an other chip, i think it doesn't works on this band.
@ EmfDev
As you see in first picture of 380-480 Mhz band the Airspy mini is very sensitive (-135 dbm for 12db S/N) , on the second picture of 380-480 Mhz band, i just
put the gain of the airspy near 0db like measure in 76-108 Mhz band, there is very low signal on 400Mhz compared to 76-108Mhz band. See the RF gain on the pictures, very low, same gain to compare)
The EMF 390 v2 indicates false signal on 380-480 Mhz band , the same signal on every places and every materials, see the image of em535 that have the same version as me. Same signal as me.
I worked 20 years in electronic and metrology, design and maintenance of metrology material and i am ham radio licenced.
I had contact with APAVE, LCIE (and GLEM for medical mesurements) in France, if you don't want to see that this material indicates falses mesures, i can contact technicians to verify , but it can be too late to return the EMF after, because i leave Paris for province.
I think the only band where the EMF390v2 works fine in 2.4-2.5 Ghz band because it use a common wifi chip and antenna for this band. |
Edited by - Yves16 on 03/13/2024 03:31:09 |
|
|
| Reply #10
Yves16
France
8 Posts |
Posted - 03/22/2024 : 10:17:40
|
No reply ?
Did you try to compare a EMF-390 in 308-480 Mhz band with em535 and my photo, i think it will look the same.
I buyed this model because we have, my neighbors and us a 10 KW FM tour at 400 meters. It is only for that, i have an Gigahertz Solution HF32D for phone mesures, that are normal.
AS it was my job, i am in charge of this question.
Is it possible to return this product, because for me, it don't work for mesuring FM or VHF band.
Cheers |
|
|
| Reply #11
EmfDev
2150 Posts |
Posted - 03/25/2024 : 09:59:05
|
| Not sure but it may be a noise from the chip. Please contact support@gqelectronicsllc.com to check for return policies. |
|
|
| Reply #12
Yves16
France
8 Posts |
Posted - 03/28/2024 : 10:45:12
|
Hello,
Your support replied me it is normal and it is a general purpose product.
I buyed this product because we have a 10 KW FM emitter at 350 meters of our house, the field mesured near the house, on ground is 1.59 V/m , the field mesured at window on first stage in view of the antenna at the same place as the photo in attachment is 3.45 V/m.
All mesure made by professional by French government.
My fieldmeter for comparaison, that is not professional, find 6 V/m in the same place professionals found 3.45 V/m (it is classical with cheap material, it indicates more but it indicates something), the EMF found 0 V/m or 0.01 to 0.03 µW/cm2 (0.19 to 0.33 V/m)
I made also mesure with the method of FM antenna + diodes with correction of antenna factor and pic value, found near 3.45 V/m at the windows of the photo, i can easily bright a led with the antenna.
So the unique band this product works is 800 Mhz - 2.5 Ghz band, where i compared with professional mesure and my HF32D fieldmeter.
So i want you to take back your product and repay because i think it is not a default of mine but a design problem.
As you can see on the photo i made today, it has not been used and is realy new, i did't charge the batterie and it is now 95 %.
Cheers
|
|
|
| |
Topic |
|
EMF 390 in 380-480 Mhz band and FM band
