Recommendation Needed for a Spectrum Analyzer

[UrbanFarmEngineer]

Hey Everyone:

I have a big RFI problem in my house and I must design a mitigation plan. I have undesirable RF coming from every possible path. Some is coming from inside the house and quite a bit from outside of the house coming in then being conducted on the household wiring. I can provide more details if needed.

My plan so far is to use a Spectrum Analyzer to identify the wavelengths that are 'victimizing' lol my residential wiring, then to use ferrites, and AC power filters to clean it up.

Could someone recommend:

1. A model of spectrum analyzer that would best suit my purpose. I don't need anything fancy with features that I won't use just something that will be effective for my purposes. I haven't used one of these since University and never used one for AC so I need advice on which model is most suited to my needs and something that is not overly complex to learn.

2. A tutorial that provides a comprehensive technical introduction to the principles of EMC/EMI filtering and optimizing its applications in residential settings. I have both common mode and differential noise as well as some near field coupling. I've never used filters before so I need to learn from scratch how they work and then where to locate them to optimize their effect. I want to get as much RFI off my household wires as possible.

Thanks! Looking forward to hearing everyone's insights.

 

[Baluncore]

Some is coming from inside the house and quite a bit from outside of the house coming in then being conducted on the household wiring. I can provide more details if needed.

Most people who go looking for RF/EMI, are on a witch hunt, driven by paranoia.
They will always find something, but not know how to interpret it.
How do you know you have an RF/EMI problem?

A Software Defined Radio, SDR, module plugged into your computer, with free public domain spectrum analyser software, should do the job at minimum cost.

When you are tired of searching, you can enjoy listening to music on the SDR.

 

[Vanadium 50]

Witch hunt? Or snipe hunt?

I had a problem in my lab many years ago. The AC power was being modulated by the university's radio station. You could pick it up everwhere - we picked it up using a tank of gas as the antenna.

"I don't know what the thing I am looking for looks like" is a terrible place to start, and a spectrum analyzer might or might not be the right tool to start. My go-to when I don't know what I am looking for is an analog scope. Unfortunately, they don't really exist any more.

 

[berkeman]

I have a big RFI problem in my house and I must design a mitigation plan. I have undesirable RF coming from every possible path. Some is coming from inside the house and quite a bit from outside of the house coming in then being conducted on the household wiring. I can provide more details if needed.

This is really too nebulous for us to be of much help. Can you say more about how you are seeing this interference manifested? What devices does it interfere with?

I had a problem in my lab many years ago. The AC power was being modulated by the university's radio station.

I had a similar issue years back in my lab where I was working on a sensitive analog circuit, and I kept getting weird noise picked up by it. I could see it on my 'scope and it didn't seem to correlate with anything in my lab. I finally decided to feed the noise into an audio amp and listen to it, and it turned out to be KGO AM radio transmitter that was about 4 miles away from my lab (broadcasting 50,000 watts). My circuit was rectifying the 1Mz AM radio signal, and I was seeing the audio with my 'scope. Lordy.

Another source for interference in homes can be if you have nearby neighbors who are HAMs. Look for large antenna structures above their homes. If you can find out that they are the source of the RFI, they are obligated to mitigate the issue. (It's best to work with them in a cooperative neighborly way, of course.)

 

[Averagesupernova]

If you can find out that they are the source of the RFI, they are obligated to mitigate the issue.

Is that really the case though? If they are within FCC regs they are not required to do much. FCC regs makes a very broad swath in this situation. All over any city with two-way and paging transmitters VHF ham receivers are often overloaded from those transmissions and it is a result of a poor front end design. Many consumer grade equipment that picks up 'noise' suffers from the same cheap design.

 

[Vanadium 50]

The OP is in Canada, so the FCC is kind of irrelevant.

Most hams want to be good citizens, so threatening with regulators is seldom necessary. But we have, as of yet, zero evidence that that is the case.

 

[berkeman]

Is that really the case though? If they are within FCC regs they are not required to do much.

If the HAM transmissions are interfering with licensed radio receivers, AFAIK the burden is on the transmitter to fix the problem. They are likely transmitting too much power or have some out-of-band harmonic distortion issues.

The OP is in Canada, so the FCC is kind of irrelevant

Looks like the ISED is applicable in Canada. The regulations are pretty similar, as you would expect for bordering countries:
https://compliancetesting.com/is-fcc-certification-accepted-in-canada/

All over any city with two-way and paging transmitters VHF ham receivers are often overloaded from those transmissions and it is a result of a poor front end design.

Yeah, we had an issue with the HAM radio setup at one of our firehouses a few years back, where we had to switch to one of our hand-held radios because the main radio had a technical problem. As were trying to run the weekly HAM practice Net on the air, we kept getting some strange beeping interference on the handheld. We had to switch to a different frequency/repeater for that Net, and spent the next few weeks trying to figure out the issue.

In the end it was because the firehouse HAM antenna on the roof had a lot higher gain than a typical handheld's antenna, and the signal from a nearby legal pager radio was overloading the front end of the handheld. If we wanted to be able to use our handheld transceivers as backups for the main radio, we would have had to build or purchase bandpass filters for the 2m and 70cm bands that we use for emergency HAM communications.

 

[wroh]

Hey Everyone:

I have a big RFI problem in my house and I must design a mitigation plan. I have undesirable RF coming from every possible path. Some is coming from inside the house and quite a bit from outside of the house coming in then being conducted on the household wiring. I can provide more details if needed.

My plan so far is to use a Spectrum Analyzer to identify the wavelengths that are 'victimizing' lol my residential wiring, then to use ferrites, and AC power filters to clean it up.

Could someone recommend:

1. A model of spectrum analyzer that would best suit my purpose. I don't need anything fancy with features that I won't use just something that will be effective for my purposes. I haven't used one of these since University and never used one for AC so I need advice on which model is most suited to my needs and something that is not overly complex to learn.

2. A tutorial that provides a comprehensive technical introduction to the principles of EMC/EMI filtering and optimizing its applications in residential settings. I have both common mode and differential noise as well as some near field coupling. I've never used filters before so I need to learn from scratch how they work and then where to locate them to optimize their effect. I want to get as much RFI off my household wires as possible.

Thanks! Looking forward to hearing everyone's insights.

How about covering the house with copper screen (Faraday cage?), if its that bad I would think 90% is coming from one primary source. You could ask your utility company to do a electrical/noise survey for you. They do not want electrical lines/equipment generating noise. Of course you can rent a spectrum analyzer of some type, the new ones almost operate themselves and the rental people will help determine what you need.

Luck!

 

[Averagesupernova]

If the HAM transmissions are interfering with licensed radio receivers, AFAIK the burden is on the transmitter to fix the problem.

That is typically what is done even though the transmitter is not defective. Hams will try to help get the device that unintentionally picks up these signals to work correctly. Electronic organs, PA systems, all kinds of gear will pick up and rectify signals from a nearby transmitter.
-
Just about any electronics gear will have this sticker:
"This device may not cause harmful interference and this device must accept any interference received, even if it causes undesirable operation."
-
It should carry some weight.

 

[Vanadium 50]

Why is HAM capitalized? When did it become an acronyn?

In any event, we really should get some data before blaming anyone. "RF" covers a lot of ground, much of which is only tangentially connected to communications.

 

[berkeman]

Why is HAM capitalized? When did it become an acronyn?

There is a whole folklore about the origins of the term HAM/Ham/ham. Nobody really knows for sure...

https://en.wikipedia.org/wiki/Etymology_of_ham_radio

"A little station called HAM"

This widely circulated but fanciful tale claims that, around 1911, an impassioned speech made by Harvard University student Albert Hyman to the United States Congress, in support of amateur radio operators, turned the tide and helped defeat a bill that would have ended amateur radio activity entirely by assigning the entire radio spectrum to the military. An amateur station that Hyman supposedly shared with Bob Almy and Reggie Murray, which was said to be using the self-assigned call sign HAM (short for Hyman-Almy-Murray), thus came to represent all of amateur radio.[17][18] However, this story seems to have first surfaced in 1948, and practically none of the facts in the account check out, including the existence of "a little station called HAM" at Harvard in the first place.[19][20][21]

In 1972, Ham Radio (magazine) editor Jim Fisk reported that Albert Hyman confirmed to him that Hyman, Robert Almy and Reginald Murray had put wireless station HAM on the air, however, it was war correspondent Percy Greenwood whose story in a New York medical publication gave the "original HAM story" its start. As told to Fisk, station HAM was not located at Harvard, but at Roxbury High School. After corresponding with Hyman, Fisk concluded that the story had nothing to do with the fact that radio amateurs are called "hams"; rather, the term goes back to the early days of wire telegraphy when unskilled, incompetent operators were pejoratively called hams by their more experienced colleagues.[22]

 

[Vanadium 50]

How about covering the house with copper screen

What? Why not just use tinfoil?

 

[Averagesupernova]

Why is HAM capitalized? When did it become an acronyn?

In any event, we really should get some data before blaming anyone. "RF" covers a lot of ground, much of which is only tangentially connected to communications.

Agreed. I can recall a case around 30 years ago there was a paging transmitter that had a spurious output on a local 2M repeater input. There was a lot of discussion about who's responsible. The hospital owned the pager and had never hired anyone for anything concerning it. Their maintenance crew installed and set it up. Soooooo, their take on it was too bad for you. Pager works fine for us so what's the problem?
-
Two way company #1 said the problem must be at the site where the hams repeater was.
-
Two way company #2 said there is definitely a signal on the hams frequency that doesn't belong there but it might not be originating in the paging transmitter although the signal peaks at the hospital where the paging transmitter is kept. It's a tall building with various other comms equipment as well. So the thought was it could be intermodulating with a signal from another transmitter. This hypothesis formed due to the fact that the signal was not getting into the hams repeater on every transmission from the pager.
-
But, upon closer inspection it was found the spurious signal was always there, it just moved around +/- 20 to 30 khz either side of the repeater input. As the pager warmed up, the spur frequency moved. So now two way company #2 who had their own equipment on the top floor of this building and had access to the site had a look. Just changing the transmission line length or putting a dummy load on the pager would move the spur. But, they weren't the owner, so all they could do was verify. A few days later, two way company #1 installed a bandpass cavity after the transmitter. I guess the fact that two way company #2 got involved stung a little bit. I don't know what kind of authorization they had doing this or if they wanted to get a maintenance contract for the pager or what. The problem went away, at least on that particular frequency. I thought it was a poor fix for the problem.
-
So things can get interesting when interference exists. In the above case I would have simply preferred to get the FCC involved but too many people didn't want to make waves.

 

[berkeman]

What? Why not just use tinfoil?

You can't solder/weld the seams with tinfoil...

 

[Vanadium 50]

You can't solder/weld the seams with tinfoil..

Two words: silver epoxy. Magic stuff. Everyone should own a bottle.

 

[Baluncore]

Cover up when out in the sun. It is wavelengths shorter than visible light, like UV and X-rays, that are ionising, and so are biologically dangerous.

RF and lower frequency radiation, with a wavelength longer than light, is thermal and so does not pose a biological problem, except heatstroke, or cooking in high power microwave environments.

Fear of the unknown can make people do funny things. Some do wear metal foil hat liners, and it works, because it does make them feel happier.

 

[russ_watters]

I had a similar issue years back in my lab where I was working on a sensitive analog circuit, and I kept getting weird noise picked up by it. I could see it on my 'scope and it didn't seem to correlate with anything in my lab. I finally decided to feed the noise into an audio amp and listen to it, and it turned out to be KGO AM radio transmitter that was about 4 miles away from my lab (broadcasting 50,000 watts). My circuit was rectifying the 1Mz AM radio signal, and I was seeing the audio with my 'scope. Lordy.

You know how they used to say you could pick up radio with braces on your teeth? I was once hired to figure out why one specific floor of a high-rise was receiving radio through....everything. Speakers, headsets, telephones, the metal window frames...everything. We never exactly figured it out except for that it was right next to its sister-tower with a radio station broadcasting at the same level. Evidently if the wattage is high enough everything is a radio receiver.

Another source for interference in homes can be if you have nearby neighbors who are HAMs.

Those people are a menace to society and should be drawn, quartered and banned.

 

[Baluncore]

Those people are a menace to society and should be drawn, quartered and banned.

If you should be so lucky as to have a ham next door. Start by offering food and drink, then ask them to explain electricity, and tell them how awesome they are.

Hams tend to be lone, fixative, problem solvers, on the spectrum in a good way. So stand or sit next to them, not facing them in confrontation. Admire with them the geometry of their fascinating artistic antennas. Allow them to explain.

Only then tell them vaguely about the interference problems you have, but don't use the word 'interference', or blame them. "My TV does not always work properly, I blame the foreign manufacturer". They will either fix your TV antenna for you, or the problem will magically go away.

Stay friends. When things need fixing, or a natural disaster happens, you have a valuable resource next door, one that responds to kindness.

If you ever find yourself with a ham, in a battle against a common enemy, you will quickly discover why you should always remain friends with your local ham.

 

[UrbanFarmEngineer]

Most people who go looking for RF/EMI, are on a witch hunt, driven by paranoia.
They will always find something, but not know how to interpret it.
How do you know you have an RF/EMI problem?

A Software Defined Radio, SDR, module plugged into your computer, with free public domain spectrum analyser software, should do the job at minimum cost.

When you are tired of searching, you can enjoy listening to music on the SDR.

How about covering the house with copper screen (Faraday cage?), if its that bad I would think 90% is coming from one primary source. You could ask your utility company to do a electrical/noise survey for you. They do not want electrical lines/equipment generating noise. Of course you can rent a spectrum analyzer of some type, the new ones almost operate themselves and the rental people will help determine what you need.

Luck!

Thanks! Yes got the PoCo out and they found some issue on one of their neutrals. I could see the difference in temp on my FLIR so they replaced the bushing and fixed the poles all up the street. So that is ruled out.
Problem is my street has a lot of old houses and many elderly owners so the electrical maintenance is not great. My nextdoor neighbor had a really bad looking power drop and as a result they had stray current along the house's water pipes, gas line, and who knows what else. PoCo fixed that one too.
I put a barrier between our houses and that took ALOT off of my power cables, ductwork, water pipes etc.
I found some wiring errors in my house and repaired those.. that helped a lot.

I got a MiniSA and I am still getting a peak at around 100MHz The higher in the house I go the stronger the power density gets. The attic is the worst.

My house is a 1950s house and the main floor is not grounded. I have two breakers that have no ground in the Romex and these are two of the offenders. The other is a ground loop between my furnace and AC. I have to filter those and I am learning about filters and ferrites so that I can understand what to get and where to put it.

But as for the attic, I don't know what is going on that is making it radiate. It is coming down through the ceiling into the main floor bedrooms.

 

[UrbanFarmEngineer]

Witch hunt? Or snipe hunt?

I had a problem in my lab many years ago. The AC power was being modulated by the university's radio station. You could pick it up everwhere - we picked it up using a tank of gas as the antenna.

"I don't know what the thing I am looking for looks like" is a terrible place to start, and a spectrum analyzer might or might not be the right tool to start. My go-to when I don't know what I am looking for is an analog scope. Unfortunately, they don't really exist any more.

i've narrowed it down using an trifield RF meter now I just need to mitigate. I just got a miniSA and it is pretty great for what I paid for it and it is showing a main spike at around 100MHz. There were a few other spikes which I found the sources of.
I need to learn the principles of filters and chokes, how they work and optimization of application.

 

[UrbanFarmEngineer]

Is that really the case though? If they are within FCC regs they are not required to do much. FCC regs makes a very broad swath in this situation. All over any city with two-way and paging transmitters VHF ham receivers are often overloaded from those transmissions and it is a result of a poor front end design. Many consumer grade equipment that picks up 'noise' suffers from the same cheap design.

But can you still do a lot inside to filter and shield?

I just threw up some chicken wire between me and next door as a test to see how much of theirs is affecting mine and it took lots of the RF off wires, ductwork, and the pipes that were near that wall.

There are some other issues that are my problem and in my house. I have to learn the technical principles/physics of how mitigation devices work.

So far I solved the circuit on one entire breaker using ferrite beads so I have hope that I can clean it up. I've got the other cables and breakers identified and diagnosed... got a ground loop issue too. As for next door... I;ve talked to them about their "emissions" but they don't care much so I will have to shield. A little bit of chicken wire trial has gone a long way so far with that so I can do something more sophisticated as a solution.

I need a really comprehensive technical instructional of how filters and ferrites work for AC residential applications.

 

[UrbanFarmEngineer]

The OP is in Canada, so the FCC is kind of irrelevant.

Most hams want to be good citizens, so threatening with regulators is seldom necessary. But we have, as of yet, zero evidence that that is the case.

That is a good idea to look for HAMs. They are usually enthusiastic about sharing their tips and diagnostic equipment too,

 

[UrbanFarmEngineer]

This is really too nebulous for us to be of much help. Can you say more about how you are seeing this interference manifested? What devices does it interfere with?


I had a similar issue years back in my lab where I was working on a sensitive analog circuit, and I kept getting weird noise picked up by it. I could see it on my 'scope and it didn't seem to correlate with anything in my lab. I finally decided to feed the noise into an audio amp and listen to it, and it turned out to be KGO AM radio transmitter that was about 4 miles away from my lab (broadcasting 50,000 watts). My circuit was rectifying the 1Mz AM radio signal, and I was seeing the audio with my 'scope. Lordy.

Another source for interference in homes can be if you have nearby neighbors who are HAMs. Look for large antenna structures above their homes. If you can find out that they are the source of the RFI, they are obligated to mitigate the issue. (It's best to work with them in a cooperative neighborly way, of course.)

Sure let me type up the list of issues I've identified.
Just give me a day or so...

 

[UrbanFarmEngineer]

Cover up when out in the sun. It is wavelengths shorter than visible light, like UV and X-rays, that are ionising, and so are biologically dangerous.

RF and lower frequency radiation, with a wavelength longer than light, is thermal and so does not pose a biological problem, except heatstroke, or cooking in high power microwave environments.

Fear of the unknown can make people do funny things. Some do wear metal foil hat liners, and it works, because it does make them feel happier.

I guess they use tinfoil hats to turn themselves into walking human antennas so they can receive the secret messages from the aliens. Too bad they don't know that the aliens aren't real and that the secret messages are actually coming from rogue CIA agents with transmitting chips in their brains, and the secret lab-grown babies from Jeffery Epstein's sperm bank/baby farm in New Mexico.

 

[UrbanFarmEngineer]

The OP is in Canada, so the FCC is kind of irrelevant.

Most hams want to be good citizens, so threatening with regulators is seldom necessary. But we have, as of yet, zero evidence that that is the case.

HAMs have been the most help so far... the ARRL have entire books on this subject and HAMs are super into their hobby so when you wanna talk about it with them they are super enthusiastic and forthcoming with accurate and researched information.

I really should look for local HAMs

 

[UrbanFarmEngineer]

If you should be so lucky as to have a ham next door. Start by offering food and drink, then ask them to explain electricity, and tell them how awesome they are.

Hams tend to be lone, fixative, problem solvers, on the spectrum in a good way. So stand or sit next to them, not facing them in confrontation. Admire with them the geometry of their fascinating artistic antennas. Allow them to explain.

Only then tell them vaguely about the interference problems you have, but don't use the word 'interference', or blame them. "My TV does not always work properly, I blame the foreign manufacturer". They will either fix your TV antenna for you, or the problem will magically go away.

Stay friends. When things need fixing, or a natural disaster happens, you have a valuable resource next door, one that responds to kindness.

If you ever find yourself with a ham, in a battle against a common enemy, you will quickly discover why you should always remain friends with your local ham.

Totally Agree. If you want to ask them anything they are overly enthusiastic to help and extremely knowledgeable. From an Asperger it is awesome to see someone else obsessed and in love with their technical hobby as we Aspies get with ours.

 

[UrbanFarmEngineer]

In summary:

...just to take the heat of the HAMs as I mentioned above it is mostly my next door neighbors who rent their house to IT guys in their 20s who have just about every kind of transmitting device, in addition to the actual house having electrical problems. Have had some neighborly discussions with them but not much success. Can't blame them. When I was in my 20s and single and living with other 20s engineers we also didn't care about anything except having fun and other peoples' issues were lost on us.

I will post a list of the specifics but for right now:
I just got my miniSA and it looks like the main offending interference is coming in at around 100MHz. I have a high spike in the 0-30 Hz range but I think that is my LED can lights. Gotta filter those. Gotta learn about filters first.

There were spikes at other frequencies but I was able to locate the cause by unplugging certain things and putting my internet modem in a metal box. Cleaned up one entire breaker/line so far using ferrite beads just by trial and error.

Found some wiring errors, solved those and the main noise decreased but did not dissapear.
RF power density is highest in the attic, lowest in the basement.
Suspected ground loop in some HVAC equipment
Other cables are conducting RF from a source inside the house and one cable runs across several others in the furnace room and those cables pickup the RF. Wrapped the one offender in aluminum screen mesh and the other cables were clean again.

Have some 50s Romex on the main floor with no ground wire: that is conducting RF.
Have a shunted neutral between two separate lines that I have been trying to find for months but haven't found it yet.
The house was not wired by an electrician and one major wiring error in the ceiling of the master bedroom... that is the hottest spot for the RF in terms of power density

Threw some chicken wire up between the houses to test how much is coming in from next door and SO much instantly dissapeared, measured it with my trifield RF meter and: power cables in that area of the house came back clean, ductwork on that side came back zero... etc.

I will take some more specific measurements and try to get some screenshots from the miniSA and post it when I post the detailed breakdown.
Thanks for all the input so far.
AND LAST I love HAMs. I secretly suspect they are all Aspies like me.

 

[Baluncore]

I guess they use tinfoil hats to turn themselves into walking human antennas so they can receive the secret messages from the aliens.

No, the tinfoil lined hat is 100% guaranteed to prevent RF mind control by the Government.

What material is the roof of your house made from?

All the signals you are observing are very low-power, so are not a threat.

 

[Vanadium 50]

Honestly, I am puzzled.

100 MHz is the middle of the FM band. What could be generating noise there?
Presumably, your problem is in receiving FM. That's pretty robust against noise. There are limits of course, and nothing is perfect, but this doesn't sound like a trouble spot.
But if the problem was receiving FM. why a spectrum analyzer? You already knew the frequency.
100 MHz is 3 m. Chicken wire seems like overkill. Maybe it's what you had around, but it shouldn't need something on that scale.

 

[Averagesupernova]

100 MHz is the middle of the FM band.

That should be the first clue. ;)

 

[UrbanFarmEngineer]

No, the tinfoil lined hat is 100% guaranteed to prevent RF mind control by the Government.

What material is the roof of your house made from?

All the signals you are observing are very low-power, so are not a threat.

That is so wrong! The tin foil hats aren't grounded so the mind control is still happening... they just WANT you to think that the tin foil hats work. Be careful out there.

Roof is made from standard material wooden frame and shingles. There are a lot of wires that run up in the attic and at least one major wiring errors.

I know that low-power seems like a non-threat but frequency and pulsation rate are key factors in biological interference. Think of the opera singer and the glass that is the most overused analogy... she can sing really loud but it's only when she hits a certain note that the glass breaks. Some frequencies can be disruptive at surprisingly low power. It just depends on the fragility of the resonant body.

Enough about all that Krazy talk tho.

I just need a good solid technical primer on how to use filters and ferrites for residential alternating current applications.

 

[UrbanFarmEngineer]

Honestly, I am puzzled.

100 MHz is the middle of the FM band. What could be generating noise there?
Presumably, your problem is in receiving FM. That's pretty robust against noise. There are limits of course, and nothing is perfect, but this doesn't sound like a trouble spot.
But if the problem was receiving FM. why a spectrum analyzer? You already knew the frequency.
100 MHz is 3 m. Chicken wire seems like overkill. Maybe it's what you had around, but it shouldn't need something on that scale.

I just used chicken wire to test how much is coming from outside. I didint leave it up. Also I didn't know the frequency at that time.

@Averagesupernova Help me understand: I am getting FM frequency and so much of it goes away when I shield ... so is this just a radio station?

I think that I have to figure out how to set the miniSA to higher frequencies. Nextdoor just upgraded their wifi router and that;s when ALOT of the RF pollution started...

OK I will be back. I am going to have to learn how to use the SA properly before I report more results.

 

[berkeman]

Nextdoor just upgraded their wifi router and that;s when ALOT of the RF pollution started...

That's in the 2-5GHz range, which pretty much only interferes with other WiFi routers.

I know that low-power seems like a non-threat but frequency and pulsation rate are key factors in biological interference.

Wait, you are worried about biological effects from this RFI that you think exists in your home? I may have missed it, but have you said yet exactly what this RFI is doing that you noticed and want to fix?

 

[Vanadium 50]

Also I didn't know the frequency at that time.

So what is the problem? What is the symptom?

If it was interference with your FM radio, you would know the frequency - it's the same as the station being interfered with. But you don't, so you didn't..

What is the symptom?

 

[Averagesupernova]

As far as I can tell you don't even have a baseline to go by. Do you know how strong the signal in various places away from your house? Until you do, you don't really know anything.