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Author Topic: Question on Carrier Current devices/equipment  (Read 1385 times)
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Alienbeing
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« on: February 04, 2009, 07:18:17 07:18 »

I am getting very strong RF interference from something on my AC Mains coming into my house. I'm in the United States just so you know. Anyway the interference is affecting the reception of ham radio equipment. I have checked out everything that could possibly cause any RF interference in my house. I actually turned off the Main Power switch and removed AC to my entire home but still receiving this interference. It's a strong signal that is strongest around 26 - 27 Mhz. Makes a loud audio buzzing sound almost like I hearing some kind of digital data signal. If I remove power to my house and bring my receiver close to the power lines outside I still receive it. I fear it is a Carrier current device or equipment that is being used by a neighbor that shares the secondary of the transformer on the pole outside. I cannot confirm this. I called the electric power company and they came and checked out things the best they could but could not locate the cause of the noise.
I'm not too familar with carrier current devices on AC lines but recently started reading about it. Does anyone know how I can detect what freqency this carrier signal it being used? I think I maybe getting harmonics from some frequency that the device is transmitting at. I can't seem to see anything on my scope 100mhz bandwidth if I look at the AC coming into my home. I guess I need to some how find out if it is really a carrier current device but not sure how to detect it and the frequency thats being used. Does anyone have any experience in this? I'm pretty sure it is not a BPL(broadband over power lines) system. That is not suppose to be available in my area.

Alienbeing

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DTiziano
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« Reply #1 on: February 10, 2009, 06:33:11 18:33 »

The linked Ebook give some information about EMC testing.
I do not find the value, but I know that the max conducting noise level allowed by the standard is in the range of few millivolt (radio has uV detection capability). To detect it you need to strongly remove the 60 hz line voltage and amplify the rest.
Conducted noise is tested till 30 MHz, radiated from 30 to 1 GHz.
Take care, opening an electrical circuit to RF is effective only if the two part of the circuit are not coupled (wire not close to each other).
Did you tray to put an EMC line filter (input and output wires must be physically well separated) to see if the noise decrease ?

http://rapidshare.com/files/196438654/Emc.rar

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Alienbeing
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« Reply #2 on: February 22, 2009, 06:28:36 06:28 »

Ok, this problem I'm having may also be coming from a faulty stepdown transformer on the pole outside my house. I'm not really sure about this because the electric company came to my house and check everything out and said all is good. Just wondering if a pole transformer can cause such noise? Still I can't determine what is the actual frequency thats causing the noise. I know I'm picking up harmonics of it on my radio equipment. I can listen to the carrier being generated on my shortwave radio and it sounds like there is data of some sort coming in with the carrier frequency. Reason I say carrier is because it is such a strong signal that never fluctuates that it's almost like a strong AM transmitter is right on my property. The signal is everywhere in my house. If I put a shortwave radio near any powerlines in my house the signal gets much stronger. This is quite strong EMI or RFI interference on powerlines.
Usually low frequency noise on powerlines won't eminate from the powerlines much I believe. So, has to be possibly over 100 khz I think for the powerlines to act as a antenna and transmit the noise. It's not really noise but looks like an AM carrier frequency with some kind of data being modulated on it. Might even be FM too. I don't know I can just hear slow digital coming in with the signal. I can't see antthing on my scope. Only hear it on the radio. I can stand in my yard and pick up the signal it' that strong. I guess thats why I was thinking it's some kind of carrier current device that a neighbor is using that is sharing the secondary winding of the pole transformer with me. Or, other wise it's just some kind of weird EMI from the pole transformer. It's just driving me nuts. I might get the FCC involved in this to take a look at the problem because the electric power won't do much.

Thanks
Alienbeing

Thanks for the Ebook too!
« Last Edit: February 22, 2009, 06:34:00 06:34 by Alienbeing » Logged
johnri
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« Reply #3 on: February 22, 2009, 06:37:41 18:37 »

HaHa, isn't it ironic that the FCC regulations are strict on HAMs who
create interference but can do nothing when someone else is causing
the interference to a HAM, until that someone is found.

If you own a Spectrum Analyzer or have access to one then this
problem of identifying the interfering signal could be narrowed down
quite easily. A few turns of a coil looped near the mains line
would then provide you with ample signal to analyze. But, very few
people have such an expensive tool at their disposal.

Since you have already found that the signal is strong around
26-27Mhz you could try locating its source like it is done in the
Fox-Hunt contests. I am sure you can rig up a hand-held directional
antenna to a suitable portable receiver (26-27Mhz is the CB Band)
to hunt down the source of the interference. Then it would just be
a matter of calling the FCC to take care of the problem.

But before you call the FCC you should rule-out one more thing lest
it cause you a lot of embarrassment. Many receivers cannot handle a
large input signal, causing an overload and instability. This usually
happens when you have a powerful AM/FM broadcaster nearby. Try
attenuating the input signal and if the interfering signal still
appears then it is probably not an intermod product.

-Good luck
« Last Edit: February 22, 2009, 06:41:09 18:41 by johnri » Logged
Alienbeing
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« Reply #4 on: February 23, 2009, 10:01:12 22:01 »

I can remove the antenna from my receiver and connect a short length of wire to antenna input and still receive the signal (in my basement). As I bring the receiver and simple wire antenna closer to an AC power outlet the signal increases quite a bit. No Spectrum anaylizer to be had. I thought of building a simple field strength meter to see where the signal is coming from and where it is strongest ie.. outside pole transformer. Maybe a tunable field strength meter of some sort. Have to research that I guess as I've never seen a commercial product that was tuneable at certain frequencies. Some how make a tuneable bandpass filter on the front end of it I guess. Anyways thanks for the suggestions. Will dig into this some more before giving the fcc a call. No AM/FM transmitters anywhere nearby, This just recently started happening. There was though I think a new cell tower put up about 1 mile away. Thing is that if I put my receiver in the car and drive away from my house (about 70 feet) the signal goes away. Clearly away then from the power lines and pole transformer.

Alienbeing
« Last Edit: February 23, 2009, 10:05:18 22:05 by Alienbeing » Logged
myheadhurts
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« Reply #5 on: March 01, 2009, 05:23:25 17:23 »

There were/are experiments regarding using the mains to carry internet traffic in the uk as the utility co's see openings in the isp market..theres also autonomous metering...which is going to br rolled out soon so they can sack all the meter readers... are they trying any of this near you..

also do you share your mains with a neighbour who uses the 120/240vac lines to run a lan..I've also noticed more noise in my audio systems since I changed all my bulbs to compact flourescents..
Rob
« Last Edit: March 01, 2009, 10:25:57 22:25 by myheadhurts » Logged
Alienbeing
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« Reply #6 on: March 02, 2009, 12:36:28 00:36 »

I actually turned off the Main Breaker switch to completely remove all power entering my house. The main switch is in my garage right where power enters into the house. After doing that the Carrier was still present on my receivers. It had less noise by was still there. By less noise I mean that if a AM transmitter was transmitting near my house without any modulation All I would have is a strong signal received with no audio content. So it appeared to be just about the same thing. Signal was still there but there was a much smaller amount of noise on the signal. It almost sounds audio wise like a low frequency clock sound. Possibly somekind of digital data. Thing is there was less of it. Possibly due maybe from less loading by electrical/electronic equipment in my house. The electrical metering box on the outside is of the remote type and can be read from a passing electrical utility truck.
The power company came and temporary removed the meter and killed the power going into my house. Still had the signal coming into my receiver (battery operated shortwave radio) mounted in my car. Again signal strength was high but less noise on it.
If I park my car which has an external antenna on the roof, for the receiver, under my powerlines going to my house the signal is stronger. So it seems to be coming from the street utility pole where the transformer is mounted. It looks to be shared with at least 2 other houses (neighbors). Internet? not from the power company in my area. Well thats what they told me. That would be Broadband Over Powerlines. No such service in my area for that. Now possibly some kind of router equipment that is connected via powerlines to computers in a neighbors house maybe just for a local home lan setup might be what is causing the problem. I actually have not seen any equipment that does that sort of thing. Thinking it would be really outdated stuff compared to wireless routers. Might be something that a neighbor is using such a an intercom system that uses a carrier current (AC power line) to transmit data between similar units. Or, possibly a security system. What is I think call an X10 system? I still have to drive my car into my neighbors driveways and see If I pick up a stronger signal. Maybe do that tomorrow when they not home. With my luck it will be a security system and call the police on  me and take videos of me sitting in their driveway
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« Reply #7 on: March 23, 2009, 10:30:36 10:30 »

I found the wiki on X10 pretty informative, might be of benefit to your QRM hunt:

http://en.wikipedia.org/wiki/X10_(industry_standard)

"...This digital data is encoded onto a 120 kHz carrier which is transmitted as bursts during the relatively quiet zero crossings of the 50 or 60 Hz AC alternating current waveform. One bit is transmitted at each zero crossing."

73
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« Reply #8 on: March 23, 2009, 10:27:38 22:27 »

I am getting very strong RF interference from something on my AC Mains coming into my house. I'm in the United States just so you know. Anyway the interference is affecting the reception of ham radio equipment. I have checked out everything that could possibly cause any RF interference in my house. I actually turned off the Main Power switch and removed AC to my entire home but still receiving this interference. It's a strong signal that is strongest around 26 - 27 Mhz. Makes a loud audio buzzing sound almost like I hearing some kind of digital data signal. If I remove power to my house and bring my receiver close to the power lines outside I still receive it. I fear it is a Carrier current device or equipment that is being used by a neighbor that shares the secondary of the transformer on the pole outside. I cannot confirm this. I called the electric power company and they came and checked out things the best they could but could not locate the cause of the noise.
I'm not too familar with carrier current devices on AC lines but recently started reading about it. Does anyone know how I can detect what freqency this carrier signal it being used? I think I maybe getting harmonics from some frequency that the device is transmitting at. I can't seem to see anything on my scope 100mhz bandwidth if I look at the AC coming into my home. I guess I need to some how find out if it is really a carrier current device but not sure how to detect it and the frequency thats being used. Does anyone have any experience in this? I'm pretty sure it is not a BPL(broadband over power lines) system. That is not suppose to be available in my area.

Alienbeing



Hi Alienbeing

the frequency you mentioned 27Mhz is a global band for all radio amateur and radio ham applications and using this band especially doesn't require license at all in any area in the world and called the "Citizen Band". so most wireless applications that require no license would be mainly using it like kids woki toki , old versions of wireless phones , remote control systems especially the ones used in alarm systems ,wireless intercom systems , most of today's micro controllers that is used in rf apps support up to 40Mhz embedded transceiver inside the micro     , etc you name the rest.

the main thing i want tell you about is
1-you should know how much this interference harms you.
2-with witch of your appliance and instruments this signal causes bad or unwanted results
3-if it mainly in the mains i suggest you use an emi filter "electro magnetic interference" filter and it's a simple series of coils with caps connected between the live and the neutral with a special values if you search google for emi filter design you will get thousands of sites telleng how to make their calculations and how you can DIY it. DIY="Do It Yourself" .
   
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Alienbeing
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« Reply #9 on: March 25, 2009, 02:19:47 14:19 »

It's comomg across pretty much every radio receiver. Even standard FM stereo reception gets interference. How the power company can get aeay with this is beyond me. They deny they have anything to do with it. They may not if if it is a neighbor running some kind of signal that is on their power line such as an X10 security sytem or an intercom possbly or even internet commections via powerlines. As long as they are sharing the seconday of transformer on the pole outside my house I will pick this stuff up on my power line. I briefly did look at Emi filters but still need to get the center frequency that is on he lines. Tried my frequency counter wih a beefed up from end (more sensitive now). Don't even need a wired direction connection to pickup low power signals. Still though I piching up a signal that fluctuates wildly. Data is being imposed on this carrier frequency FSK, or FM I think.
I should go mobile and drive around close to my neighbors homes an see if I can pick up a stronger signal. Just I might need to sit in their driveway to get close enough. Would look kind of suspicious and would probably have the police called on me. I suspose If I asked them nicely they will let me survey their outside wiring for signal leakage. It woul have to be bothering them or other neighbors the same way. I just have t be certain it's not the power company doing this. Though maybe for awhile I was being bugged wirelessly bu the feds or CIA or obama for some reason. Never know these days. Could be maybe I listen to Rush Limbaugh too much and I'm targeted like he is by the Democrates and Obama and the media. Even with power completely removed from my house by killing the main breaker in my garage I'm still receiving a very strong signal coming from the powerlines outside going to my house. So, it's affecting FM radio reception, CB radio reception (the worst), and Ham Radio Shortwave. Haven't checked out Standard over the air tv reception yet. The odd thing is that the more electrical load I have in my house the stronger the interference becomes.
Been looking to build a tunable field strength meter for 2-30 mhz to see if I can narrow down the center carrier frequency seeing I don't have a spectrum analyzer to use. Hoping I can borrow one from work someday. I'm currently out of work on disability due to breaking my arm in a car rollover accident. Just been one of those years where everything seems to wrong.

Thanks for your replies it greatly appreciated. Always good to talk technicial issues with people on here.

Alienbeing
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« Reply #10 on: March 28, 2009, 03:51:45 15:51 »

I suspect some kind of broadband of powerline noise issue as already mentioned. Ask all your neighbours connected to the same sub transformer if they have recently installed a computer networking product to distribute connections around their property. Also asking your neighbours if they are suffering from noise problems, maybe they already know the answer.

Also more info here:

http://bplinterference.wikispaces.com/

Good luck solving this.. it sounds a pain in the ass. I would be annoyed as hell if it were happening to me.
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« Reply #11 on: March 29, 2009, 11:43:23 11:43 »

Dear Alienbeing,

1) are you sure unwanted noise moves in your house wiring from main AC line? if it's so, try adding (just for testing) a 1:1 transformer just to check if noise comes from that path.

2) are you sure noone close 2 U have got an RF transmitter ? if it's so and you'd like to remove noise you'd have to use shielded cables in your house. (unfortunately it cannot be done i think).

3) try to check if noise come from remote open-gate units (alarms). it often happens that some unit do not have a proper coupling and an excessive power is emitted....

take a nice dig.

;-)

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