Advice for research project on detecting appliance use from radiated EMF noise #RTL #experiment #gnuradio #airspydiscovery


Nathan R <nario98@...>
 

Hi all,

I am a graduate student currently exploring a new research project on activity recognition within a household setting by sensing when a user turns on or interacts with a particular appliance or electric device. The intent behind the project is to wirelessly detect device use by passively measuring the EMF noise that these devices emit through the air during regular use. Through past literature searches, we have identified the very low frequency range of 0-2 MHz as the target area where many of these devices are emitting noise. I did not have a lot of knowledge on antenna and radio design coming into this project, and only limited experience with SDRs, but have made some headway in the past few weeks. My setup thus far has consisted of using an RTL-SDR V.3 in direct sampling mode paired with a variety of pre-made antenna designs, of which I have achieved the best results with the MegaLoop 30+ MLA. I have also just ordered an Airspy HF+ Discovery and the Youloop antenna which I hope will help me to achieve even better SNR in the HF range.

From my readings and my background knowledge in electromagnetics, I have come to understand that these loop antennas perform better in the very low frequency ranges, but also couple to the magnetic component of radio waves. This appears to match with my experimental results where although I have been able to detect a variety of appliances and devices, such as TVs, washing machines, and light bulbs, it is only devices that generate strong magnetic fields, like power drills with DC motors, that I am able to detect from more than a foot away.

Especially once we get the new Airspy SDR, I am fairly confident in all of the areas of our pipeline except the antenna design. Thus my question is if there is anyone who, either purposely or accidentally, has had experience with detecting appliances from longer distances before, suggestions on how we could improve our antenna design for these lower frequencies, and thoughts on whether detecting these waves through the air at a house or room scale is even realistically possible at all.

Thanks


David Ranch
 


Hello Nathan,

Sounds like a very interesting research project and I imagine a LOT of people could learn from your findings!


One thought though: you mentioned this research was going to be "EMF noise that these devices email through the air" but I've always been curious if they are also radiating noise via the AC power lines as well.  Much like the electric or magnetic interference, this "conducted" interference on the AC lines could also help you find and detect things potentially even farther away.  I have to believe there can be a way to couple an SDR to the power line, cancel out the 50/60 cycle power, and view things in the frequency and/or time domains.

Anyway.. good luck with the research!

--David
KI6ZHD


On 07/09/2020 11:01 AM, Nathan R wrote:
Hi all,

I am a graduate student currently exploring a new research project on activity recognition within a household setting by sensing when a user turns on or interacts with a particular appliance or electric device. The intent behind the project is to wirelessly detect device use by passively measuring the EMF noise that these devices emit through the air during regular use. Through past literature searches, we have identified the very low frequency range of 0-2 MHz as the target area where many of these devices are emitting noise. I did not have a lot of knowledge on antenna and radio design coming into this project, and only limited experience with SDRs, but have made some headway in the past few weeks. My setup thus far has consisted of using an RTL-SDR V.3 in direct sampling mode paired with a variety of pre-made antenna designs, of which I have achieved the best results with the MegaLoop 30+ MLA. I have also just ordered an Airspy HF+ Discovery and the Youloop antenna which I hope will help me to achieve even better SNR in the HF range.

From my readings and my background knowledge in electromagnetics, I have come to understand that these loop antennas perform better in the very low frequency ranges, but also couple to the magnetic component of radio waves. This appears to match with my experimental results where although I have been able to detect a variety of appliances and devices, such as TVs, washing machines, and light bulbs, it is only devices that generate strong magnetic fields, like power drills with DC motors, that I am able to detect from more than a foot away.

Especially once we get the new Airspy SDR, I am fairly confident in all of the areas of our pipeline except the antenna design. Thus my question is if there is anyone who, either purposely or accidentally, has had experience with detecting appliances from longer distances before, suggestions on how we could improve our antenna design for these lower frequencies, and thoughts on whether detecting these waves through the air at a house or room scale is even realistically possible at all.

Thanks


jdow
 

In the 1980s people were picking up emissions from CRT type monitors (all we had) and painting local copies of the screens based on intercepted noise. That is why TEMPEST criteria were invented for military electronics.

You betcha they radiate, over the air, over network wires, over power wires, over anything you can imagine. The trick is to somehow make that radiation not correlate with what you are doing.

{^_-}

On 20200709 14:26:06, David Ranch wrote:
Hello Nathan,
Sounds like a very interesting research project and I imagine a LOT of people could learn from your findings!
One thought though: you mentioned this research was going to be "EMF noise that these devices email through the air" but I've always been curious if they are also radiating noise via the AC power lines as well.  Much like the electric or magnetic interference, this "conducted" interference on the AC lines could also help you find and detect things potentially even farther away.  I have to believe there can be a way to couple an SDR to the power line, cancel out the 50/60 cycle power, and view things in the frequency and/or time domains.
Anyway.. good luck with the research!
--David
KI6ZHD
On 07/09/2020 11:01 AM, Nathan R wrote:
Hi all,

I am a graduate student currently exploring a new research project on activity recognition within a household setting by sensing when a user turns on or interacts with a particular appliance or electric device. The intent behind the project is to wirelessly detect device use by passively measuring the EMF noise that these devices emit through the air during regular use. Through past literature searches, we have identified the very low frequency range of 0-2 MHz as the target area where many of these devices are emitting noise. I did not have a lot of knowledge on antenna and radio design coming into this project, and only limited experience with SDRs, but have made some headway in the past few weeks. My setup thus far has consisted of using an RTL-SDR V.3 in direct sampling mode paired with a variety of pre-made antenna designs, of which I have achieved the best results with the MegaLoop 30+ MLA. I have also just ordered an Airspy HF+ Discovery and the Youloop antenna which I hope will help me to achieve even better SNR in the HF range.

From my readings and my background knowledge in electromagnetics, I have come to understand that these loop antennas perform better in the very low frequency ranges, but also couple to the magnetic component of radio waves. This appears to match with my experimental results where although I have been able to detect a variety of appliances and devices, such as TVs, washing machines, and light bulbs, it is only devices that generate strong magnetic fields, like power drills with DC motors, that I am able to detect from more than a foot away.

Especially once we get the new Airspy SDR, I am fairly confident in all of the areas of our pipeline except the antenna design. Thus my question is if there is anyone who, either purposely or accidentally, has had experience with detecting appliances from longer distances before, suggestions on how we could improve our antenna design for these lower frequencies, and thoughts on whether detecting these waves through the air at a house or room scale is even realistically possible at all.

Thanks


Greg Ella
 

For the lower end of the HF band, 0.1 to 10 MHz, an amplified loop is a good choice because a dipole would be so big,  A lot of appliances radiate up into VHF and UHF, where a smaller directional antenna like a Yagi becomes practical.  My next door neighbor just got LED strip lights for his garage, and I pick them up 200 feet away on 144 MHz with a 5 element Yagi.  A few years ago I was seeing clusters of strange narrow band signals between 6.5 and 7.1 MHz.  I tracked them down to a digitally controlled pottery kiln 2 miles away.  When I got within a block of the source, I could easily pick it up with an 18 inch mag mount whip and an
Airspy HF+.

Greg Ella
N0EMP


On Thu, Jul 9, 2020 at 3:27 PM David Ranch <airspy-groupsio@...> wrote:

Hello Nathan,

Sounds like a very interesting research project and I imagine a LOT of people could learn from your findings!


One thought though: you mentioned this research was going to be "EMF noise that these devices email through the air" but I've always been curious if they are also radiating noise via the AC power lines as well.  Much like the electric or magnetic interference, this "conducted" interference on the AC lines could also help you find and detect things potentially even farther away.  I have to believe there can be a way to couple an SDR to the power line, cancel out the 50/60 cycle power, and view things in the frequency and/or time domains.

Anyway.. good luck with the research!

--David
KI6ZHD


On 07/09/2020 11:01 AM, Nathan R wrote:
Hi all,

I am a graduate student currently exploring a new research project on activity recognition within a household setting by sensing when a user turns on or interacts with a particular appliance or electric device. The intent behind the project is to wirelessly detect device use by passively measuring the EMF noise that these devices emit through the air during regular use. Through past literature searches, we have identified the very low frequency range of 0-2 MHz as the target area where many of these devices are emitting noise. I did not have a lot of knowledge on antenna and radio design coming into this project, and only limited experience with SDRs, but have made some headway in the past few weeks. My setup thus far has consisted of using an RTL-SDR V.3 in direct sampling mode paired with a variety of pre-made antenna designs, of which I have achieved the best results with the MegaLoop 30+ MLA. I have also just ordered an Airspy HF+ Discovery and the Youloop antenna which I hope will help me to achieve even better SNR in the HF range.

From my readings and my background knowledge in electromagnetics, I have come to understand that these loop antennas perform better in the very low frequency ranges, but also couple to the magnetic component of radio waves. This appears to match with my experimental results where although I have been able to detect a variety of appliances and devices, such as TVs, washing machines, and light bulbs, it is only devices that generate strong magnetic fields, like power drills with DC motors, that I am able to detect from more than a foot away.

Especially once we get the new Airspy SDR, I am fairly confident in all of the areas of our pipeline except the antenna design. Thus my question is if there is anyone who, either purposely or accidentally, has had experience with detecting appliances from longer distances before, suggestions on how we could improve our antenna design for these lower frequencies, and thoughts on whether detecting these waves through the air at a house or room scale is even realistically possible at all.

Thanks


Edward MacDonald
 

Nathan,

I believe they definitely emit some. At least in the case of computer monitors. Great Scott on you tube uploaded a video a few days ago where he demonstrates eaves dropping on a monitors screen image using SDR#, an AirSpy mini and some other software I can't exactly recall, but he picked up the signal from the actual cable connecting the monitor from the computer. It's an interesting video.

On Thu., Jul. 9, 2020, 3:27 p.m. David Ranch, <airspy-groupsio@...> wrote:

Hello Nathan,

Sounds like a very interesting research project and I imagine a LOT of people could learn from your findings!


One thought though: you mentioned this research was going to be "EMF noise that these devices email through the air" but I've always been curious if they are also radiating noise via the AC power lines as well.  Much like the electric or magnetic interference, this "conducted" interference on the AC lines could also help you find and detect things potentially even farther away.  I have to believe there can be a way to couple an SDR to the power line, cancel out the 50/60 cycle power, and view things in the frequency and/or time domains.

Anyway.. good luck with the research!

--David
KI6ZHD


On 07/09/2020 11:01 AM, Nathan R wrote:
Hi all,

I am a graduate student currently exploring a new research project on activity recognition within a household setting by sensing when a user turns on or interacts with a particular appliance or electric device. The intent behind the project is to wirelessly detect device use by passively measuring the EMF noise that these devices emit through the air during regular use. Through past literature searches, we have identified the very low frequency range of 0-2 MHz as the target area where many of these devices are emitting noise. I did not have a lot of knowledge on antenna and radio design coming into this project, and only limited experience with SDRs, but have made some headway in the past few weeks. My setup thus far has consisted of using an RTL-SDR V.3 in direct sampling mode paired with a variety of pre-made antenna designs, of which I have achieved the best results with the MegaLoop 30+ MLA. I have also just ordered an Airspy HF+ Discovery and the Youloop antenna which I hope will help me to achieve even better SNR in the HF range.

From my readings and my background knowledge in electromagnetics, I have come to understand that these loop antennas perform better in the very low frequency ranges, but also couple to the magnetic component of radio waves. This appears to match with my experimental results where although I have been able to detect a variety of appliances and devices, such as TVs, washing machines, and light bulbs, it is only devices that generate strong magnetic fields, like power drills with DC motors, that I am able to detect from more than a foot away.

Especially once we get the new Airspy SDR, I am fairly confident in all of the areas of our pipeline except the antenna design. Thus my question is if there is anyone who, either purposely or accidentally, has had experience with detecting appliances from longer distances before, suggestions on how we could improve our antenna design for these lower frequencies, and thoughts on whether detecting these waves through the air at a house or room scale is even realistically possible at all.

Thanks


jdow
 

Um, er, ah, perhaps you should drag open the books that explain some RF reality to you. The first consideration is learning the actual noise characteristics of the environment in which you are working. At LF and below it is difficult to setup a receiver plus antenna system with performance that is not limited by ambient noise, even in the middle of the ocean or desert or some other utterly deserted area. A bit of looking will reveal a lot of information. Even (gasp shudder) Wikip-whatever it is can get you started.

For normal (unamplified) antennas you can remove the antenna. If the noise goes down you have a low enough receiver noise figure already. Improvement will prove impossible. It's not quite to easy with an amplified loop.

The chief limitation you will experience is dynamic range. An RTLSDR dongle is severely limited in this regard. So without a filter that drops the AM broadcast band about 40 dB or more the bare RTLSDR dongle MAY prove to be problematic. The AirSpy HF+ dongles will do better; but, even they will significantly benefit from an AM broadcast band notching filter.

An interesting resource for your perusal might be the ARRL archives.
http://www.arrl.org/sounds-of-rfi is one semi interesting point. Several QRM hunting and identifying sites exist. "Use the Web, Luke."

(And if you are a college student your college should have an excellent library available for your browsing, in better times. Were I a mentor for a PhD or Masters thesis candidate I'd worry that you do not sound well prepared for what you are trying to do. If you are a quick self-learner by all means dive in. You have a lot to learn, which means you have a lot of moments of satisfaction and even elation as new concepts become clear to you.)

{^_^} Joanne

On 20200709 11:01:01, Nathan R wrote:
Hi all,
I am a graduate student currently exploring a new research project on activity recognition within a household setting by sensing when a user turns on or interacts with a particular appliance or electric device. The intent behind the project is to wirelessly detect device use by passively measuring the EMF noise that these devices emit through the air during regular use. Through past literature searches, we have identified the very low frequency range of 0-2 MHz as the target area where many of these devices are emitting noise. I did not have a lot of knowledge on antenna and radio design coming into this project, and only limited experience with SDRs, but have made some headway in the past few weeks. My setup thus far has consisted of using an RTL-SDR V.3 in direct sampling mode paired with a variety of pre-made antenna designs, of which I have achieved the best results with the MegaLoop 30+ MLA. I have also just ordered an Airspy HF+ Discovery and the Youloop antenna which I hope will help me to achieve even better SNR in the HF range.
From my readings and my background knowledge in electromagnetics, I have come to understand that these loop antennas perform better in the very low frequency ranges, but also couple to the magnetic component of radio waves. This appears to match with my experimental results where although I have been able to detect a variety of appliances and devices, such as TVs, washing machines, and light bulbs, it is only devices that generate strong magnetic fields, like power drills with DC motors, that I am able to detect from more than a foot away.
Especially once we get the new Airspy SDR, I am fairly confident in all of the areas of our pipeline except the antenna design. Thus my question is if there is anyone who, either purposely or accidentally, has had experience with detecting appliances from longer distances before, suggestions on how we could improve our antenna design for these lower frequencies, and thoughts on whether detecting these waves through the air at a house or room scale is even realistically possible at all.
Thanks


jdow
 

Future generations of DisplayPort, HDMI, and DVI should all grow an encryption protocol for this reason. Just the same, I still automatically giggle at the idiots who think I'd fall for their claim to have videos of me masturbating to internet porn. Sorry, that's (mostly) a boy problem.

{^_-}

On 20200709 16:36:05, Edward MacDonald wrote:
Nathan,
I believe they definitely emit some. At least in the case of computer monitors. Great Scott on you tube uploaded a video a few days ago where he demonstrates eaves dropping on a monitors screen image using SDR#, an AirSpy mini and some other software I can't exactly recall, but he picked up the signal from the actual cable connecting the monitor from the computer. It's an interesting video.
On Thu., Jul. 9, 2020, 3:27 p.m. David Ranch, <airspy-groupsio@... <mailto:airspy-groupsio@...>> wrote:
Hello Nathan,
Sounds like a very interesting research project and I imagine a LOT of
people could learn from your findings!
One thought though: you mentioned this research was going to be "EMF noise
that these devices email through the air" but I've always been curious if
they are also radiating noise via the AC power lines as well.  Much like the
electric or magnetic interference, this "conducted" interference on the AC
lines could also help you find and detect things potentially even farther
away.  I have to believe there can be a way to couple an SDR to the power
line, cancel out the 50/60 cycle power, and view things in the frequency
and/or time domains.
Anyway.. good luck with the research!
--David
KI6ZHD
On 07/09/2020 11:01 AM, Nathan R wrote:
Hi all,

I am a graduate student currently exploring a new research project on
activity recognition within a household setting by sensing when a user
turns on or interacts with a particular appliance or electric device. The
intent behind the project is to wirelessly detect device use by passively
measuring the EMF noise that these devices emit through the air during
regular use. Through past literature searches, we have identified the very
low frequency range of 0-2 MHz as the target area where many of these
devices are emitting noise. I did not have a lot of knowledge on antenna
and radio design coming into this project, and only limited experience
with SDRs, but have made some headway in the past few weeks. My setup thus
far has consisted of using an RTL-SDR V.3 in direct sampling mode paired
with a variety of pre-made antenna designs, of which I have achieved the
best results with the MegaLoop 30+ MLA. I have also just ordered an Airspy
HF+ Discovery and the Youloop antenna which I hope will help me to achieve
even better SNR in the HF range.

From my readings and my background knowledge in electromagnetics, I have
come to understand that these loop antennas perform better in the very low
frequency ranges, but also couple to the magnetic component of radio
waves. This appears to match with my experimental results where although I
have been able to detect a variety of appliances and devices, such as TVs,
washing machines, and light bulbs, it is only devices that generate strong
magnetic fields, like power drills with DC motors, that I am able to
detect from more than a foot away.

Especially once we get the new Airspy SDR, I am fairly confident in all of
the areas of our pipeline except the antenna design. Thus my question is
if there is anyone who, either purposely or accidentally, has had
experience with detecting appliances from longer distances before,
suggestions on how we could improve our antenna design for these lower
frequencies, and thoughts on whether detecting these waves through the air
at a house or room scale is even realistically possible at all.

Thanks


jdow
 

Did it take a letter from the FCC or did he listen to you when you gently informed him he was radiating illegal signals. Or has nothing happened at all?

{o.o}

On 20200709 16:12:57, Greg Ella wrote:
For the lower end of the HF band, 0.1 to 10 MHz, an amplified loop is a good choice because a dipole would be so big,  A lot of appliances radiate up into VHF and UHF, where a smaller directional antenna like a Yagi becomes practical. My next door neighbor just got LED strip lights for his garage, and I pick them up 200 feet away on 144 MHz with a 5 element Yagi.  A few years ago I was seeing clusters of strange narrow band signals between 6.5 and 7.1 MHz.  I tracked them down to a digitally controlled pottery kiln 2 miles away.  When I got within a block of the source, I could easily pick it up with an 18 inch mag mount whip and an
Airspy HF+.
Greg Ella
N0EMP
On Thu, Jul 9, 2020 at 3:27 PM David Ranch <airspy-groupsio@... <mailto:airspy-groupsio@...>> wrote:
Hello Nathan,
Sounds like a very interesting research project and I imagine a LOT of
people could learn from your findings!
One thought though: you mentioned this research was going to be "EMF noise
that these devices email through the air" but I've always been curious if
they are also radiating noise via the AC power lines as well.  Much like the
electric or magnetic interference, this "conducted" interference on the AC
lines could also help you find and detect things potentially even farther
away.  I have to believe there can be a way to couple an SDR to the power
line, cancel out the 50/60 cycle power, and view things in the frequency
and/or time domains.
Anyway.. good luck with the research!
--David
KI6ZHD
On 07/09/2020 11:01 AM, Nathan R wrote:
Hi all,

I am a graduate student currently exploring a new research project on
activity recognition within a household setting by sensing when a user
turns on or interacts with a particular appliance or electric device. The
intent behind the project is to wirelessly detect device use by passively
measuring the EMF noise that these devices emit through the air during
regular use. Through past literature searches, we have identified the very
low frequency range of 0-2 MHz as the target area where many of these
devices are emitting noise. I did not have a lot of knowledge on antenna
and radio design coming into this project, and only limited experience
with SDRs, but have made some headway in the past few weeks. My setup thus
far has consisted of using an RTL-SDR V.3 in direct sampling mode paired
with a variety of pre-made antenna designs, of which I have achieved the
best results with the MegaLoop 30+ MLA. I have also just ordered an Airspy
HF+ Discovery and the Youloop antenna which I hope will help me to achieve
even better SNR in the HF range.

From my readings and my background knowledge in electromagnetics, I have
come to understand that these loop antennas perform better in the very low
frequency ranges, but also couple to the magnetic component of radio
waves. This appears to match with my experimental results where although I
have been able to detect a variety of appliances and devices, such as TVs,
washing machines, and light bulbs, it is only devices that generate strong
magnetic fields, like power drills with DC motors, that I am able to
detect from more than a foot away.

Especially once we get the new Airspy SDR, I am fairly confident in all of
the areas of our pipeline except the antenna design. Thus my question is
if there is anyone who, either purposely or accidentally, has had
experience with detecting appliances from longer distances before,
suggestions on how we could improve our antenna design for these lower
frequencies, and thoughts on whether detecting these waves through the air
at a house or room scale is even realistically possible at all.

Thanks


Greg Ella
 

I wrote them a letter explaining that I was a radio hobbyist that lives a few miles from them, and that I was picking up some strong
RFI from something in their house that turns on at 7:00 PM every night.  I told them that it was not adversely affecting anything I do
and I was not complaining, I was just curious about the source.  I also cautioned them that equipment that radiates like this might be defective,
and might also present a shock and fire hazard.

They replied back that the wife had a pottery store, and ran a kiln with a digital controller in the garage every evening.  A few weeks later the
noise stopped, so maybe they got it serviced or upgraded.

Greg Ella
N0EMP


On Fri, Jul 10, 2020 at 2:59 AM jdow <jdow@...> wrote:
Did it take a letter from the FCC or did he listen to you when you gently
informed him he was radiating illegal signals. Or has nothing happened at all?

{o.o}

On 20200709 16:12:57, Greg Ella wrote:
> For the lower end of the HF band, 0.1 to 10 MHz, an amplified loop is a good
> choice because a dipole would be so big,  A lot of appliances radiate up into
> VHF and UHF, where a smaller directional antenna like a Yagi becomes practical. 
> My next door neighbor just got LED strip lights for his garage, and I pick them
> up 200 feet away on 144 MHz with a 5 element Yagi.  A few years ago I was seeing
> clusters of strange narrow band signals between 6.5 and 7.1 MHz.  I tracked them
> down to a digitally controlled pottery kiln 2 miles away.  When I got within a
> block of the source, I could easily pick it up with an 18 inch mag mount whip
> and an
> Airspy HF+.
>
> Greg Ella
> N0EMP
>
> On Thu, Jul 9, 2020 at 3:27 PM David Ranch <airspy-groupsio@...
> <mailto:airspy-groupsio@...>> wrote:
>
>
>     Hello Nathan,
>
>     Sounds like a very interesting research project and I imagine a LOT of
>     people could learn from your findings!
>
>
>     One thought though: you mentioned this research was going to be "EMF noise
>     that these devices email through the air" but I've always been curious if
>     they are also radiating noise via the AC power lines as well.  Much like the
>     electric or magnetic interference, this "conducted" interference on the AC
>     lines could also help you find and detect things potentially even farther
>     away.  I have to believe there can be a way to couple an SDR to the power
>     line, cancel out the 50/60 cycle power, and view things in the frequency
>     and/or time domains.
>
>     Anyway.. good luck with the research!
>
>     --David
>     KI6ZHD
>
>
>     On 07/09/2020 11:01 AM, Nathan R wrote:
>>     Hi all,
>>
>>     I am a graduate student currently exploring a new research project on
>>     activity recognition within a household setting by sensing when a user
>>     turns on or interacts with a particular appliance or electric device. The
>>     intent behind the project is to wirelessly detect device use by passively
>>     measuring the EMF noise that these devices emit through the air during
>>     regular use. Through past literature searches, we have identified the very
>>     low frequency range of 0-2 MHz as the target area where many of these
>>     devices are emitting noise. I did not have a lot of knowledge on antenna
>>     and radio design coming into this project, and only limited experience
>>     with SDRs, but have made some headway in the past few weeks. My setup thus
>>     far has consisted of using an RTL-SDR V.3 in direct sampling mode paired
>>     with a variety of pre-made antenna designs, of which I have achieved the
>>     best results with the MegaLoop 30+ MLA. I have also just ordered an Airspy
>>     HF+ Discovery and the Youloop antenna which I hope will help me to achieve
>>     even better SNR in the HF range.
>>
>>     From my readings and my background knowledge in electromagnetics, I have
>>     come to understand that these loop antennas perform better in the very low
>>     frequency ranges, but also couple to the magnetic component of radio
>>     waves. This appears to match with my experimental results where although I
>>     have been able to detect a variety of appliances and devices, such as TVs,
>>     washing machines, and light bulbs, it is only devices that generate strong
>>     magnetic fields, like power drills with DC motors, that I am able to
>>     detect from more than a foot away.
>>
>>     Especially once we get the new Airspy SDR, I am fairly confident in all of
>>     the areas of our pipeline except the antenna design. Thus my question is
>>     if there is anyone who, either purposely or accidentally, has had
>>     experience with detecting appliances from longer distances before,
>>     suggestions on how we could improve our antenna design for these lower
>>     frequencies, and thoughts on whether detecting these waves through the air
>>     at a house or room scale is even realistically possible at all.
>>
>>     Thanks
>
>




Glen Rhinesmith
 

You may want to use an attenuated antenna to first obtain a library of patterns while in close proximity of each device.
Most EMI receivers utilize a band pass filter to narrow the band width to the frequencies of interest.
(Stoddart 92198-3 antenna coupler, or Electro Metrics ALR-25M).
These have schematics that can be found on-line that may give you some ideas for your project.
They will also work with the Airspy Discovery without an extra preamp.
73 and Good Luck with your project,
Glen


jdow
 

That was VERY nicely handled, Greg.

{^_^}

On 20200710 07:48:10, Greg Ella wrote:
I wrote them a letter explaining that I was a radio hobbyist that lives a few miles from them, and that I was picking up some strong
RFI from something in their house that turns on at 7:00 PM every night.  I told them that it was not adversely affecting anything I do
and I was not complaining, I was just curious about the source.  I also cautioned them that equipment that radiates like this might be defective,
and might also present a shock and fire hazard.
They replied back that the wife had a pottery store, and ran a kiln with a digital controller in the garage every evening.  A few weeks later the
noise stopped, so maybe they got it serviced or upgraded.
Greg Ella
N0EMP
On Fri, Jul 10, 2020 at 2:59 AM jdow <jdow@... <mailto:jdow@...>> wrote:
Did it take a letter from the FCC or did he listen to you when you gently
informed him he was radiating illegal signals. Or has nothing happened at all?
{o.o}
On 20200709 16:12:57, Greg Ella wrote:
> For the lower end of the HF band, 0.1 to 10 MHz, an amplified loop is a good
> choice because a dipole would be so big,  A lot of appliances radiate up
into
> VHF and UHF, where a smaller directional antenna like a Yagi becomes
practical.
> My next door neighbor just got LED strip lights for his garage, and I
pick them
> up 200 feet away on 144 MHz with a 5 element Yagi.  A few years ago I was
seeing
> clusters of strange narrow band signals between 6.5 and 7.1 MHz.  I
tracked them
> down to a digitally controlled pottery kiln 2 miles away.  When I got
within a
> block of the source, I could easily pick it up with an 18 inch mag mount
whip
> and an
> Airspy HF+.
>
> Greg Ella
> N0EMP
>
> On Thu, Jul 9, 2020 at 3:27 PM David Ranch <airspy-groupsio@...
<mailto:airspy-groupsio@...>
> <mailto:airspy-groupsio@...
<mailto:airspy-groupsio@...>>> wrote:
>
>
>     Hello Nathan,
>
>     Sounds like a very interesting research project and I imagine a LOT of
>     people could learn from your findings!
>
>
>     One thought though: you mentioned this research was going to be "EMF
noise
>     that these devices email through the air" but I've always been curious if
>     they are also radiating noise via the AC power lines as well.  Much
like the
>     electric or magnetic interference, this "conducted" interference on
the AC
>     lines could also help you find and detect things potentially even farther
>     away.  I have to believe there can be a way to couple an SDR to the power
>     line, cancel out the 50/60 cycle power, and view things in the frequency
>     and/or time domains.
>
>     Anyway.. good luck with the research!
>
>     --David
>     KI6ZHD
>
>
>     On 07/09/2020 11:01 AM, Nathan R wrote:
>>     Hi all,
>>
>>     I am a graduate student currently exploring a new research project on
>>     activity recognition within a household setting by sensing when a user
>>     turns on or interacts with a particular appliance or electric
device. The
>>     intent behind the project is to wirelessly detect device use by
passively
>>     measuring the EMF noise that these devices emit through the air during
>>     regular use. Through past literature searches, we have identified
the very
>>     low frequency range of 0-2 MHz as the target area where many of these
>>     devices are emitting noise. I did not have a lot of knowledge on antenna
>>     and radio design coming into this project, and only limited experience
>>     with SDRs, but have made some headway in the past few weeks. My
setup thus
>>     far has consisted of using an RTL-SDR V.3 in direct sampling mode paired
>>     with a variety of pre-made antenna designs, of which I have achieved the
>>     best results with the MegaLoop 30+ MLA. I have also just ordered an
Airspy
>>     HF+ Discovery and the Youloop antenna which I hope will help me to
achieve
>>     even better SNR in the HF range.
>>
>>     From my readings and my background knowledge in electromagnetics, I have
>>     come to understand that these loop antennas perform better in the
very low
>>     frequency ranges, but also couple to the magnetic component of radio
>>     waves. This appears to match with my experimental results where
although I
>>     have been able to detect a variety of appliances and devices, such
as TVs,
>>     washing machines, and light bulbs, it is only devices that generate
strong
>>     magnetic fields, like power drills with DC motors, that I am able to
>>     detect from more than a foot away.
>>
>>     Especially once we get the new Airspy SDR, I am fairly confident in
all of
>>     the areas of our pipeline except the antenna design. Thus my question is
>>     if there is anyone who, either purposely or accidentally, has had
>>     experience with detecting appliances from longer distances before,
>>     suggestions on how we could improve our antenna design for these lower
>>     frequencies, and thoughts on whether detecting these waves through
the air
>>     at a house or room scale is even realistically possible at all.
>>
>>     Thanks
>
>