Mysterious RFI Resolved
Richard L. Hall (Lee) (NY4T)
on
February 13, 2004
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I am a ham operator from Murfreesboro, TN and am primarily a contester. A couple of weeks ago, I began experiencing severe RFI on 10-17 meters. The sound was similar to a heartbeat and registered 7-8 S-units on my Kenwood TS450. My first thought was to make sure the noise wasn't coming from somewhere in my house. After cycling through the circuit breakers in order, I was satisfied that the noise was from an external source.
I called a friend about 1/4 mile away and asked him to listen for the noise. He had no copy on it at all. My next approach was to borrow one of the new HT's which pretty much receives all modes DC-to-daylight. Equipped with the HT and an old CB antenna I started sniffing around the neighborhood. It didn't take long since the signal got stronger as I approached my next-door neighbor's house. Fortunately, we are friends with these folks, I keep them supplied with my homegrown produce all summer and the topper, their son is also a ham.
So, my neighbor didn't think I was a complete wacko when I presented her with my dilemma. She was curious as to what could be causing the noise as well so we started scanning her house. I asked if she had purchased any new electronic devices in the past few weeks and her answer was no. Our scan, however, led us to a device that re-defines the term electronic. On the bed in the master bedroom was a brand new electric blanket. Although the blanket was plugged in and not powered up it was sure spitting out the RF. I assume the signal was probably at the microwatt level but the wires in the blanket probably acted as an antenna giving it enough clout to ruin 10 and 15 meters for me about 100 feet away.
So, for any of you who encounter a heartbeat-like sound on the high bands, this is something you might want to consider. I am not sure whether the RFI is due to poor quality control or poor design but I did contact the company who imported these blankets (from China of course) to make them aware of the problem. The offending device was a Perfect Fit, Safe and Warm, Queen size, low-voltage electric blanket. It is imported and distributed by the Chattam and Wells Company.
73,
Lee Hall (NY4T)
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Mysterious RFI Resolved
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by N4OZI on February 13, 2004
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Here's their URL:
http://www.chattamandwells.com/index.html
Allen Cutts
N4OZI
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Mysterious RFI Resolved
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by K3XT on February 13, 2004
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I have had similar noise experiences. One turned out to be the battery charges for new portable drills. I have Dewalt and Panasonic drills and both chargers generate noise, mostly in the 28 Mhz region (noise cycled on and off). The absolute worst noise generator I have encountered was an AC wall adapter that powered a floor standing reading lamp. The noise was strong and covered the entire HF spectrum. I have also had problems with some floor standing halogen lamps. The solution for these lamps was to plug them into an AC surge protector that had RFI filtering built-in.
Sean – K3XT
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Mysterious RFI Resolved
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by KR9Q on February 13, 2004
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Thank you for posting this. I have had the same heartbeat type pulse on 17-10 since the friday before the super bowl. It just appeared and it is quite annoying. I will call my neighbors and see If they have got any new blankets.
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RE: Mysterious RFI Resolved
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by K5DVW on February 13, 2004
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It's not only electric blankets that do this, but water bed heaters. I've had the same problem due to that. In this case it was a periodic buzzing.
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Mysterious RFI Resolved
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by KR9Q on February 13, 2004
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Follow up to earlier post......My neighbor had purchased the same electric blanket. I asked her to unplug it and the noise went away. Are there any ideas for suppressing this so she can leave it plugged in?
Thanks again, 17 is alive again
Jack
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Mysterious RFI Resolved
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by KE5GK on February 13, 2004
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Lee's account is very similar to a friend's search for RFI. My friend, also a CW buff and from "4" land, roamed the neighborhood at night when the RFI would appear. His search involved not only a portable radio, but bumping light poles with his car to see if a transformer or broken insulator was the source of the RFI. (Hams, don't try this at home!)
His search finally focused on one particular house.
He rang the door bell and was greeted by a man in his PJ's. After explaining who he was and why he got the man out of bed,the usual questions followed: Do you have a mixer or arc welder on? Any new appliances? etc.
The now fully awake man replied that the only thing that he had turn on was an electric heating pad which he used each night for a bad back.
My friend was now hot on the trail. He asked to examine the heating pad. The man concurred and brought a very old heating pad to the door. My friend quiclky spotted a badly frayed cord at the base of the heating pad. The frayed cord was actually arcing and spewing out RFI that so frustrated my friend.
Here's where diplomacy meets the road. My friend told the man of the potential danger of the faulty heating pad and offerred to buy the man a new one in exchange for the old one. The man concurred and all was quiet on the ham bands once again, all but for the rare DX my friend sought.
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RE: Mysterious RFI Resolved
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by AD7DB on February 13, 2004
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I've been trying to do something about a local noise source for over a year. I know about where it's coming from but I don't know what it is. It is a solid S9 level on ALL HF bands from BCB up to 6m, including TV channels 2,4,5. There isn't a channel 3 around here but I can even see the interference on there! It doesn't look like modulated voice on the TV screen, it looks like very fine motor noise, or perhaps some kind of digital noise. It renders those channels nearly unwatchable at times.
It started about a year ago, coming on for 1 minute, off for 4 minutes. It's 24 hours a day.
Around this past Christmas, the pattern changed. Now it was on for 5 seconds, off for 5 seconds. Still 24 hours a day.
One day I put my IC-706 in my truck with the 8 foot whip and cruised the neighborhood. You could pick up the interference for an 8th of a mile around (half of a long block in this area). I found the hot spot about 300 feet west down the street from my house. On 20 meters, even with the attenuator kicked in, it was 20 dB over S9!
A neighbor was washing his car in his driveway right close to the hot spot, and was watching me go up and down the street. I moved VERY slowly, stopping for a few moments, then moving on. The neighbor put down his cleaning rag and went into his house.
That night the noise was gone. I thought my troubles were solved.
Nope. It was back again a few nights later, same as before.
Maybe the neighbor did something that day. Maybe not.
I have some ideas about it. 1. Cable TV line problem. 2. BPL that nobody's said anything about yet. 3. Some other data transmission service on the poles. 4. Somebody with a wireless LAN trying something funny like juicing up the power. 5. Some other digital wireless device radiating like nobody's business.
My plans are to check with my local ARRL rep to see if there is an interference committee or something that can identify the interference and help me do something about it. Needless to say, my HF activity from home is QRT because of it.
Dave AD7DB Van Nuys CA
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by WA3KYY on February 13, 2004
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I recently tracked down a mysterious RFI problem to my own house. I was hearing a 4 sec on 4 sec off wide buzz on discrete frequecies all throughout the HF bands to at least 15M. Of course they would appear right on the frequency I was trying to have a QSO on.
It turns out it was being generated by an Ionic Breeze air purifying unit that we had recently bought. Turning the unit off cleared up the noise. I suspect the switching supply in the unit which pulses on and off to charge the attactor plates. When I get the change. I'll see if a brute force AC line filter will cure the problem but for now I just turn the unit off when I want to operate.
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RE: Mysterious RFI Resolved
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by WB2WIK on February 13, 2004
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This was great advice.
I wish more hams who *find* the sources of their RFI would publish the information so we can all benefit. If not a full "article," at least a posting in the "RFI" section of this website would be very helpful.
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Mysterious RFI Resolved
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by K4LFK on February 13, 2004
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I HAVE ALSO EXPERIENCED VERY STRONG INTERFENCE ON SIX METERS AND WEAKER SIGNALS ON TWO METERS. I TRACED THE PROBLEM TO A NEIGHBORS HOUSE. THEY KEEP A BOAT IN THE GARAGE WITH BATTERY CHARGER. I BELIEVE IT TO BE A SWITCHING SUPPLY TYPE CHARGER, BUT I DID NOT GET A NAME OR MODEL. REMOVING THE POWER CORD STOPPED THE INTERFERENCE. I TRIED ADDING A LINE FILTER WHICH DID NOT HELP. MY EXPERIENCE HAS BEEN THAT SWITCHING SUPPLIES THAT ARE NOT PROPERLY DESIGNED INCLUDING COMPUTER SUPPLIES CAN OFTEN CAUSE INTERFERENCE PROBLEMS. 73 LEN K4LFK
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by K6FUZ on February 13, 2004
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I once had a case where I traced a periodic buzzing emission to the house of a neighbor about two blocks away. After they agreed to a search of their house I found it was an old style electromechanical alarm clock! It was the kind with the 60hz motor inside that was sold in discount stores everywhere.
They were most responsive to my discovering the source of interference as they had been getting the buzzing sound on their broadcast radios and televisions and were quite upset about it!
Needless to say, they were quick to get rid of that clock.
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RE: Mysterious RFI
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by KJ7XJ on February 13, 2004
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I am hoping that AD7DB is able to find and fix the RFI in his neighborhood. I had a similar experience which turned out to be (or I believe to be) the local cable company. Last winter (2002) I started to get noise that wiped out HF and my 2M rig. I drove around the neighborhood and found that on my AM radio in the car, I was getting noise right below a specific telephone pole a block and a half from my house. I called the local power company, had them out, and they said everything checked out. I had the phone company out, and same results. I had the cable company out, they said they were working on that pole, but assured that nothing they were doing would cause RFI. There is a clump of wires on this pole that are just hanging down covered with electrial tape. I have seen the local cable company working on this clump. The noise has gone away since Ive inquired, but it still appears from time to time with no certain weather patterns or time (night/day) to guess why. My point is, dont hesitate to call the local companies and have them look into RFI, its their job to keep these things in a clean and working order. I dont know why the company has this clump of wires hanging down, but at the moment my noise is gone. Good luck to those folks still tracking their RFI! See ya on the air
de KJ7XJ Eric Tacoma,WA ..
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by N6HVP on February 13, 2004
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Mine was one of those touch-on lamps the neighbor had. Caused terrible hash on the low bands but I found the noise level changed with the lamp intensity every time I keyed down so I would wait until it was at the lowest level before listening around.
Drove my neighbor nuts too since she thought something "spiritual" was switching her lamp on and off. We finially reached an agreement - I bought her a new lamp (manually switched) and donated her old one to Goodwill. (For some reason I thought the other next-door neighbor who frequented thrift shops would eventually buy the same lamp from Goodwill - hihi. So far so good).
Mike
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by G3SEA on February 13, 2004
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Here is an odd RFI source discovered when I worked for an RFI Dept in the U.K.
TV's over a wide area experienced severe herringbone
intereference always at a certain time of night.
Patient DF'ing in our vans pinpointed a light bulb in the toilet of a residential house ! This bulb was ' taking off ' in a wide frequency swath of interference : )
Yes, Hams were at first suspected :(
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by NY4T on February 13, 2004
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My neighbor returned the blanket and traded it for a Sunbeam blanket in the same price range. She then called me on the phone and asked me to see if there was any problem. No problem with the Sunbeam blanket powered up or not.
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Mysterious RFI Resolved
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by N0VUB on February 13, 2004
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I too had a serious RFI problem. I found that construction workers across the alley at a new middle school that was being built had a tig welder that was putting terrible hash on the hf bands, didn't matter where. I went over and asked how long they were going to be there with this problem and they fortunately were just about done. Had it for a month, drove me nuts trying to figure that one out. Another interference problem that I had for along time and went away when the next door neibor moved, come to think of it their daughter had a water bed with heater within close range of my antenna system...go figure.
73
Mark
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Mysterious RFI Resolved
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by KE2IV on February 14, 2004
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After reading your original post and a few replies, I can only add this (hopeful) thought.
Fads for electric blankets come and go.
They are a low end item.
Although the bulk of humanity is too stupid to realize that heat rises - they, generationally, buy these things. Fortunately, they ususally follow the instructions to NOT PUT THEM UNDER THEMSELVES!
Thank goodness, or we'd have a lot more charred bodies to discard.
But, since heat rises, these things ultimately prove almost useless when placed ABOVE the sheets.
So then folks realize they've been had and the stupid blankets disappear for ten years or so....
And then another stupid generation comes along...
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Mysterious RFI Resolved
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by WA2JJH on February 14, 2004
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I remember an episode from an old TV show(HAZEL 1950'1960's)
A ham was blammed for RFI. The ham was a new kid to this town. Of course the whole town was in awe of this space age hobby.
'
Then a strange loooking dude from the FCC came by with a weird contraption. A box with a loop antenna on it. A poor mockup for a DF, I ever did see. However it made the point.
The RFI was found to be the electric blanket of the complaintant! The compliantent was so humbled, he purchased a world clock for the ham he complained about.
Many of the new cheap phones pick up RFI. Wrapping a few turns of the phone line in a snap on RF core solves the problem.
The big problem is trying to explain to non hams that it is their el cheapo equipment that will either be subseptable or be the actaul cause of the RFI.
Improper installation of Cable TV is another issue that the ham is guilty, before proven innocent.
I do not go around complaining that the new hot thing are consumer WLANS. They have rendered my ATV reception on 2.4 GIG F.U.B.A.R.! The only 2.4 GIG ATV repeater is off the air for a few years now. So the issue is moot.
I am cool about it. Those that have falsely accused my HRO of causing RFI, I still give out info on what electronics to buy for XMAS. A simple apology does the trick! Some want me to elemer them to become hams now.
However, I think some just want to get their ticket so they can become PAID RFI consultants!
Heating blankets are a fad. I agree they are also dangerous. Not as bad as smoking in bed. However burn units across the U.S.A. do have the stats. on major 2nd a 3erd degree burns they have caused.
73 DE MIKE
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Mysterious RFI Resolved
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by K2WH on February 14, 2004
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Lee, NY4T, the original poster, just verified the noise I am hearing up here in NJ as the very same thing. I sent him a recording of my "Heartbeat" noise and he says "Yep, that's it"!
Now I just have to introduce myself to my neighbors across the lake.
K2WH
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by N8FVJ on February 14, 2004
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I been fortunate due to the closest neighbor is about a 1/4 mile away. I did have a problem with a touch lamp. It made a hash type noise without even being operated.
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Mysterious RFI Resolved
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by M0CUS on February 14, 2004
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Well it seems most of you have sorted you rfi noise problems. I also have an rfi problem which started at xmas. It covers the 18,21 and to a lesser extent 24 mhz bands. The noise just sounds like an FM frequency with no signal but it gives me 60db over 9 down to 10db over 9 on 24 mhz. I can turn my 2 element quad towards the direction and have got it down to 4 houses. Problem now is finding exactly what is causing the noise. I have tried using a scanner but as soon as I get close to any of the houses the meter goes full scale even without an antenna plugged in. So if anyone in the Warwickshire area of the UK can help I would be grateful. My email is M0CUS@AOL.COM
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by AH6RR on February 14, 2004
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When I became active again in July of last year I was so stoked to get my TS-520. I built a 20 and 40 meter Double Bazooka's thinking that I would work a lot of 20 meters got the rig fired up and on 20 and had a 10db over s9 noise so I went to 40 no noise at all cool. Well I made a sked with a freind in Tennesee on 20 and the noise was s 7 but his signal was s9 so I put up with it. That monday I hunted and looked with a portable radio anf found many suspect area's so I called the local power company. Thay came out with thier new toy a WIDE band recevier and a hand held yagi and checked out the neiborhood. They did find some problems in thier power system but not my noise source. They hooked it unit to my antenna to get a picture of the noise and went hunting again well to make a long story short we found the problem. My landlord upstairs has a Orion 19" TV/VCR combo that has a very noisy low voltage power supply I have tried to get intouch with the importer's of this fine POS to no avail. I guess my next move is to file a complaint with the FCC on these tv's I have tried everything I could think of to filter it and it makes the noise on or off as long as it it plugged in (I turn the breaker off when they are not home) any suguestions?
Cant work 20 with it plugged in.
Roland AH6RR
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Reverse RFI Question
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by NG1I on February 14, 2004
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My daughter in the next room has one of the capacitance lights you just touch and it goes on, touch again and gets brighter, and touch again to turn it off.
When I work 40M CW, her lamp goes crazy, on and then off, that cycle, and she has to unplug it. Now keeping it unplugged keeps me happy but I'm only part of the equation.
Does any know how to shield the lamp from this or is is the nature of these kind of table lamps?
73
Frank
MA
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RE: Mysterious RFI Resolved
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by NG1I on February 14, 2004
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Take a look at http://www.allcorp.com/, they have ALL manner of power supplies and you might find a better made one there. It worked for me when I needed an 8.5VAC 1AMP wall PS for my Heatkit Keyer. No one else had or even though anything was made in that voltage.
Frank
MA
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Mysterious RFI Resolved
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by WA2JJH on February 14, 2004
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A FINE POS? That is very funny! He is your landlord.
Dipomacy is key. If you can get your hands on a cheap POS that does not interfere. Ask him if you can demonstrate. Make sure you POS does not interfere.
If you show him that a random POS does not cause the interference, and that ham radio plays some type of AUX
type of homeland defense, maybe you could split the differene on a POS. If you can show him a model POS with more features, that can help
Let him think he is getting a better POS. You can also put in some snap on ferrits from radio shack on the line cord. Buy one of those cheap power strips that have some capacitors across the line.
To make the deal go smoother, tell him you can recommend all sorts of electronic security and other electronic advice for the building for free for a limited time.
I say limited time, because you do not want this guy to make you an unpaid electronics handyman. You do not want him calling you up with any building electrical problem. This does happen.
I did a video editing job for a client.The president of the company was very impressed. He just assumed since I did one job, where my personal input made it a good piece...I would be available for personal input on anthing electronic. I gave him a few tips. After the third phone call and not a mention of another editing job.....I just slammed the phone down on him.
I can read people all too well. He only needed one video produced. No more work. He was going to ask about
his cable TV hook up. Enough MR nice guy.
Trick is to get you foot in the door. Tell him you were noticing his nice deluxe POS. Have some casual talk. Tell him how the prices on wiress security cameras are dirt cheap. ect. Seqway into how for less money he can get a better POS. Then tell you can always tell when his POS is on. He will be curious and say prove it!
So after he thinks you have ESP powers, you tell him that his POS is radiating enough so that just about anybody with a radio shack police scanner, shortwave rcvr, kids FRS walkie talkie and the *OTHER PEOPLE* will know what he is watching and when!
Again this is a worst case scenario for a intractable person. You probably can just reason with him, before you go into all the *spook special ops routine*(HI-HI)
Hope this is appicable to your situation.If not sorry for the 2 cents of literary trash!!!!!!!
73 DE MIKE
Of course you will have to taylor you pitch to you particular situation
You can also say that if his POS is causing interference to you, it could be causing interference on frequencies the GVT or big business use. If you see a cell phone site or any other type of non TV antenna, tell him HE could be interfering with *THOSE* PEOPLE!
When he asks who are *THOSE* People, you just shake you head side to side, and say......You just do not want to be interfering period!
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by WB4QNG on February 14, 2004
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This is all fine and dandy but I am sure glad I don't have any RFI from my neighbors. I can see the headlines now One Dead Ham when neighbor tells him his equipment is a piece of junk.
Terry
WB4QNG
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RE: Mysterious RFI Resolved
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by N0RTU on February 14, 2004
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Greetings All
Just a word of caution here folks.
If you think your noise source is coming from ANY power line equipment, CALL YOUR POWER COMPANY FIRST!
Most distribution systems today utilize voltages from 7200 up to 34,500. These same systems can deliver fault currents that border on the unreal!
Smacking a utility pole with a sledge hammer,(a favorite passtime of some folks in my area) or otherwise trying to "bump" or shake a utility pole may turn out to be the last thing you ever do!
Pole mounted transformers can weigh anywhere from 200 to 2000 pounds each. If something is already loose or broken on the pole, your "nudge" may be the straw that breaks the camels back. Don't take a chance. Call your power company and let someone who has been trained to handle this type of situation come check things out.
They should want to know about noise because the noise is often a sign that something is about to fail on their line.
It's often WAY cheaper to change out a lightning arrester or other such item before it fails and burns a line down. Outages are not only a real pain for you, but they are big buck losses for the power company.
"Snooping" for noise is often necessary, and sometimes even fun, but please stay away from all power line equipment.
Linemen have the tools, training, and experience to handle these problems safely. Step back and let them do their job.
73 and Safe Hamming to All
Mike
N0RTU
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Mysterious RFI Resolved
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by KC8RKL on February 15, 2004
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About 10 years ago, as an SWL (before I re-licensed), I was plagued by sporadic RFI. I purchased a book- Interference Handbook by William R. Nelson WA6FQG. It was very helpful and easy to read. I would recommend it to anyone reading this post. WA6FQG was an RFI investigator for Southern California Edison and knows his stuff. William Orr W6SAI edited the book. BTW, I have no connection whatsoever with Mr. Nelson, Mr. Orr, their publishers, or any book distributors.
Anyhow, as for my problem, turns out it was two problems. First, I had- of all things- a problem night light in my home. It was a typical 4 watt night light with an integral photocell- the kind you simply plug into a wall outlet. Using a battery powered SW receiver, I isolated the problem by first tripping my home's main breaker and then branch circuit breakers. The night light wasn't simply an "on or off" device! Under certain conditions (morning, evening, or overcast days) it would flicker. The light from the 4W bulb could influence the photocell via an optical feedback path (reflective nearby objects), generating HF hash. The effect was most evident in dim ambient light. I could force it into this state in a totally dark room by holding the palm of my hand about 6 inches in front of the photocell. Goodbye night light.
Unfortunately, it was not the end of the story. My Hallicrafters S-85 receiver still sounded like an arc welder on damp days. Worse, the noise was still present in my battery powered receiver when I tripped the main circuit breaker. I drove around with the battery powered receiver in my car and mapped the noise. It was apparently being conducted and radiated by the power lines on my road and on a road north of my home. The noise was loudest on the road to the north, which is in an industrial area. So, I complained to the power company. After a few calls, I got the name and phone number of one the power company's RFI investigators. I faxed him a "map" of the RFI, identifed the affected frequencies, and described the noise as well as I could. The map showed the RFI as hatched areas next to the affected roads, with the depth of the hatched area representing a somewhat subjective signal strength. Within a couple of weeks, the utility found and replaced an arcing insulator on a pole on the road to the north, about a half mile away, eliminating the problem. The investigator told me that if I had stood under the pole, I would have heard the arcing. It pays to be persistant, well informed, and somewhat sympathetic. Just start counting the number of power poles in your immediate area, and realize that each pole has dozens of pieces of hardware which could be creating problems! And if the RFI source is in one of the homes or businesses nearby, the investigator's time is wasted- it's simply not the utility's problem.
Joe Fahrenholtz
KC8RKL
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I sense a great need
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by KC2ELS on February 15, 2004
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A website with a recording of the sounds of different kinds of interference and what causes them could do the hobby a great service. This article identifies the "heartbeat" sound as a blanket, other comments have described other sounds and what they represent.
Does anyone have the webspace and the interest to maintain a site like this?
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RE: I sense a great need
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by N6HBJ on February 15, 2004
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KE2IV,
yes heat rises, however electric blankets work very well to warm the user. Well enough to make you sweat if turned up too high. You see heat is also conducted through the lower sheets and as the air between the lowest sheet and the user warms up - so does the user.
Mike N6HBJ
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RE: I sense a great need
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by N6HBJ on February 15, 2004
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........another way to look at it: Heat is radiated in ALL directions from the blanket. So although the heat will eventually rise, it is constantly being replaced by "new" heat waves that radiate from the blanket. So electric blankets are very effective.........
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Mysterious RFI Resolved
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by W5RMZ on February 15, 2004
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WELL... IF THE BLANKET RESONATES THAT GOOD....PUT IT UP ON YOUR POLE AND DRIVE IT WITH LEGAL LIMIT. (SORRY,I COULDN'T RESIST.) ALL IN GOOD FUN!!!
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Mysterious RFI Resolved
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by D9AL on February 15, 2004
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Hmmm, a heating blanket antenna? Well we already have a ''FAN DIPOLE'', so i guess heating blanket quad is OK!(hi-Hi)
Serousely however Steve(WB2WIK/6) had a good idea. Some type of registery of the more RFI causing home divicses..
Have a univeral data base for these devices on the type of RFI they cause. Have streaming auidio and deo files.
Group their, products by fuction, and what Their interference signiture on a TV,radio,or Ham radio.
Simuations can be done by using a progRam called MATLAB.
The simpfied database should be readable by all that are interested.
The system can work like this, somebody has an RFI comlpaint. They do the best DF work they an to find the source. Once you have that pattern if interference.
A matlab simultion can be run.
O f course if your niegbors are nice about it, they can supply a list of appiencies they are using.
I guess heating pads would have a high coefficent of interence. That can be plugged into the simutaion.
Run the simulation.
The possible culprites come up on the simulation
One can purchase the student verion of Matlab with RF simulink for about $125
73 DE MIKE
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RE: Mysterious RFI Resolved
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by KC0LPV on February 16, 2004
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>One can purchase the student verion of Matlab with
>RF simulink for about $125
>
>73 DE MIKE
I regularly use Matlab in my research and studies
and I highly recommend it to anyone needing
mathematical/simulation software. When I get time,
I'm going to learn how to do smith charts...
However, read the license ( www.mathworks.com )
and see the student version license requirements:
"Student Use
MATLAB Student Version is for students only. It is
for use in conjunction with courses at degree
granting institutions. We offer the license as a
special service to the student community and ask
for your help in seeing that its terms are not
abused.
Professional and commercial use is prohibited."
If you want to buy it as a student, you should
contact teh Mathworks and see if you qualify. I
would argue (to them) that a ham is non-profit
(by law) and that the entire ham hobby is
educational. They may or may not let you have
the student license. If there is enough
interest, perhaps they would offer (through ARRL
perhaps) the student license to any licensed ham.
Jim kc0lpv
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RE: Mysterious RFI Resolved
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by WY7I on February 17, 2004
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One of the worst RFI problems I had turned out to be an aquarium heater...the water and fish were gone, but they never unplugged the heater. After we discovered the source of the RFI, they were real happy to disconnect it and prevent a possible fire.
The noise it generated, by the way, was an on/off pulse about every 5-10 seconds.
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Mysterious RFI Resolved
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by WA2JJH on February 17, 2004
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Hmmmm, seems like heating devices of all shapes, sizes and applications seem to be a more frequent culprit then one would at first think.
I had my own HOT experience with heating devices.
One of them was a plug in space heater. They draw a kilowatt or more sometimes.
If you notice noise (buzzing like in sound) or RFI only on cold days, you may have found a very pedestrian source.
Many people buy these el cheapo space heaters for the winter. when the buildings boiler is not hot enough.
I had a tenent in my building thath had a space heater. The one she used,o had exposed glowing hot nichrome wire. It also had a cheap rheostat.
At first she did not want to hear about how it is interfering with my ham radio. Then a few days later a horrible accident in another part of the city made the newpaper.
Someone also had a cheap space heater. One of the kids was playing around. You know how kids can be.
Some how a flammable liquid spilled on the hot exposed nichrcome wire array. A fire started. Fortunity nobody was badly hurt.
The nieghbor than asked me sheepishly about her heater. I looked it up in consumers report. It was not even listed in consumers report. She told me she bought it for 19.95 at a discount store.
She purchased the one that was rated the most instrinsicly safe. Nothing is listed for RFI in consumers. However I guessed a more expensive one, wold have less RFI. Lucky, bt educated guess.
Sure enough my RFI problem was solved!
Perhaps HAMS should take photographes of spectrum anaysers when they find a consumer device that cause RFI.
As Steve's idea, set up a database of RF spectrum from house hold devices. Even fish heaters!
Perhaps some type of universal number rating can simplify the spectral analysis.
Something like mean power output multiplied by the mean spectra of frequncies. A device with a 1, would be considered almost RFI free.
A device with a 10. should have an FCC sticker on it. The same way we have effiency ratings on air conditioners.
Consumers should be more RFI pollution conscience.
Maybe get a rebate if they buy minimal stray RF producing appliences.
One would think the BPL people would like the idea too! Perhaps the cost of making appiences almost RFI free, should be passed on to the BPL corps!
I would imagine that any appience that could pump it's RFI back into the AC line, would cause trouble for BPL. Hmmmmmmm, forget the idea I just had in my head! Hopefully IEEE 802 a-b-G and the new 5 GHZ wireless laptop service will render BPL obsolete!
Again, I like the idea of a RFI database of appliances.
73 DE MIKE
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RE: Mysterious RFI Resolved
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by WEATHERLAWYER on February 17, 2004
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[q]It started about a year ago, coming on for 1 minute, off for 4 minutes. It's 24 hours a day.[/q]
This sounds like a fridge or freezer. You'd be doing them a favour telling them, if they were using an old machine. I bet it is using quite a lot of power.
The only other things it might be is a central heating pump or air conditioner. But seasonal and durnal differences rule out those.
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RE: Mysterious RFI Resolved
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by WEATHERLAWYER on February 17, 2004
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[q] Again, I like the idea of a RFI database of appliances. [/q]
One for telephones and telephone mastst would go down well in the UK at the moment.
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Website to report RFI problems, possible solutions
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by W5UNX on February 19, 2004
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I volunteer. I should have something basic setup sometime later tonight. Stay tuned for details
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RE: Website to report RFI problems, possible solut
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by N4KIT on February 20, 2004
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Thanks W5UNX, look forward to seeing what you set up.
A suggestion for those of us spectrum-analyzer-deficient hams. Short audio clips of interference would be useful. A "Category" classification would be good for searching different types of RFI. For example, this is (generally) what power line noise sounds like or this is (generally) what heating devices sound like.
Fortunately, I live in a rural area and am blessed with a pretty "RFI quiet" environment, though I am supprised I have not had to deal with electric fence issues, with the number in the 10 sq. mile area around my house!
Thanks for this type of post, it is very useful to read about others' experiences in tracing down various types of RFI.
73, Chris N4KIT
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RE: Website to report RFI problems, possible solut
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by WB6CVR on February 20, 2004
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Excellent thread. Here's a suggestion I tried, but it didn't help. I have a warbling noise at many spots on various bands that sound like an unstable drifting fax signal. Many different receivers hear the same sound at the same place. The sound itself seems to drift around in frequency.
Here's my suggestion: the next time you have a complete power failure in your neighborhood, fire up your rig on a battery and listen. All electrical devices in the neighborhood should be OFF, then you can really see if the problem is local or not. In my case, the warbling was still there.
73
Eric
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RE: Mysterious RFI Resolved
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by N1RKT on February 20, 2004
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Well that is going to be a tough introduction. Hello may I visit your bed?
Good Luck!
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RE: Mysterious RFI Resolved
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by K4PM on February 22, 2004
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I must be one of the bulk of humanity too stupid to realize that heat rises. Hi Hi.
In Physics, I was taught that heat does not rise, but that hot air does indeed rise. Heat is thermal energy that can be transferred to a body by conduction, radiation or convection and is called the science of heat transfer. Usually, heat is transferred from the higher temperature body to the lower temperature body until an equilibrium is finally reached as the higher temp body gets colder and the lower temp body getting hotter. (Remember energy can neither be created nor destroyed but only tranformed from one form to another.) In some cases where work is involved the opposite can be true but with the example of the heating blanket the former is the true example of what is happening.
Not trying to critize or flame but just to correct a well intentioned point of which I belived the same thing until my Physics teacher corrected me some 43 odd years ago. Brings back lots of memories.
Getting back on track with the topic of RFI, when I was about 16 or so, with the CB callsign KOK4092, I was experiencing S9 plus 20-30 intermittently on my CB rig using a 5 element yagi at 65 feet. I noticed it was the worst on windy days. I notified the local power company and they came out with a very expensive rf receiver with rabbit ears and could not find anything. I persuaded them to come into the house and hook up their receiver to my yagi to get the direction. Later they came back and told me that they had found the problem. Seems that about a mile away, someone had thrown a short piece of wire over a 7200 volt line and as the wind would blow and move the wire them the RFI was worse. When the wire was removed all my RFI problems ceased. Hope this helps someone.
Rick K4PM
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RE: Mysterious RFI Resolved
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by KC8YFT on February 22, 2004
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would be the laws of thermodynamics, if i'm not mistaken.....sir newton?
anyhoo, i too get a very anoying (and intermitent) level of niose. mostly around 11 and 10m. though i am not endorsed to xmit on 10m - i do still listen. it's helping (i hope) to build my CW skills. but the noise covers everything below, say a s9. reading this forum has given me a couple of ideas, maybe i will investigate a cheap ceiling fan...i also get something that interferes with the tv. sounds like "splatter." um, for lack of a better word. like a harmonic, but i'm guessing that's what it "should" sound like. i'm thinking it's the local police department, interfering with their mobile comms. but i can't verify this on the scanner....yet
incidentally, that's the only run of cable that accepts interference, and the only one the cable co. installed.
hmmmmm. maybe i've missed my calling in life.
73's
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RE: Website to report RFI problems, possible solut
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by W5UNX on February 24, 2004
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Well, I'm a bit delayed on this. I won't get into a whiney rant (although it would probably make me feel better). I don't have anything at the moment, but for future reference, the website will be http://RFIdb.us/
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RE: Reverse RFI Question
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by KB7EFZ on May 13, 2004
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If it's a metal base table lamp (common for these) then you can open the base, remove the touch circuit, and replace the lamp holder with one with a switch. I did that to one of the two fine touch lamps I bought my lovely wife when we were younger. Now only one light in the family room can copy my CW...
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RE: Mysterious RFI Resolved
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by WB5WPA on June 1, 2004
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To date, I've tracked down or otherwise found the following RFI producers that substantially impacted the HF or broadcast services:
o Guest model 2623 battery charger (last year - 2003)
-- Located next door on neighbor's bass boat
-- Effects 80 Meter band predominantly, some effects present on 40M but to lesser degree
-- Effect in AM Broadcast band includes interference on the local regional on 990 KHz;
-- An in-line AC line filter (like a Corcom brand OEM) insufficient to 'cure' noise on 80 M
-- Manual claims device meets "FCC Part 15 Class A computing" device noise specs
o "Terminator Scooter" battery charger (on 5-31-2004)
-- Website URL on scooter: www.terminatorscooter.com
-- Chargers labeled "Made in China"
-- No FCC label on charger (contrary to FCC Part 15 reqmts)
-- No FCC 'label' in manual (also contrary to FCC part 15 reqmts)
-- Many of these seem to be sold 'dealers' at flea markets
o Treadmill - make unknown (2004)
-- Located next door - at same neighbor's w/bass boat
-- Strong enough to affect several *Regional* AM Broadcasters in the area!
-- Visibly affects broadcast VHF-Lo TV Chs (2,4,5) in the area with digital swirling 'noise' dots and lines
-- 'Commercial' Treadmills seem to be qualified to FCC "Class A computing device" noise specs
o AC Power Distribution system - '3-phase cap bank' (2 yrs ago) also known as "Power Factor Correction" or MVAr bank or 'Reactive Power sources'
-- VERY noisy bank about a mile away
-- Located by DFing on 80M using a portable SW receiver with internal loopstick ant.
-- Note: these are often run by a timer which is mounted at eye-level. The time on this one was easily noted when it 'fired up' in the morning
-- Another one of these just got 'noisy' this last week - and I have already tracked it down
-- This 'new' noisy cap bank also produces lots of RFI in the 136 MHz range - which was easily 'hearable' on a hand-held scanner that has an AM aircraft band
o Noisy lamp pole - lamp off during day (5-31-2004)
-- Pole is actually *audibly* noisy - noise can be heard in/coming from metal pole!
-- Interference is very 'spikey' abd random in nature, low rep rate within sinusiod 'peak' exciting so noise-producing mechanism
----- Best piece of DF equipment I have found for locating this stuff in the HF bands:
A Sears 4-band Portable Radio Model 2278 covering AM/FM/SW and both AC line and battery powered using a 5" long ferrite loopstick on AM/SW1 as well as the telescopic whip antenna for FM/SW ... plus a built-in **Signal Strength meter** (THIS is worth more than its weight in Gold for close-in locating in strong noise fields!)
This 4-band receiver was purchased in 1968 - I was 13 at the time and little did I realize the vital part that radio would play later on in tracking down EMI/RFI ...
Here's a picture of this 4-band Sears radio:
http://www.dallas.net/~jvpoll/PortableSearsRadioMvc-013fbs.jpg
If someone ever runs across another one of these - give me a ring! My e-mail is good on QRZ dot com.
de Jim WB5WPA
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RE: I sense a great need
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by KB2VXA on May 5, 2005
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Hi all,
"The investigator told me that if I had stood under the pole, I would have heard the arcing."
Now what do you do when you're bracketed by two 13KV feeders each a block away? At night when it's quiet I can hear creepage on every insulator on every pole wherever those lines go. I can hear the "arcing" noise from 160M to 6M (and beyond when it's a particularly damp night, gets MUCH louder too) typically S5-7. This is common all along the shore, the closer to the water the worse it is so besides moving inland I believe nothing can be done about it. Sea spray and high voltage simply don't mix.
Hmmm, I guess if BPL comes to town I'll never notice. (;->)
73 de Sparky KB2VXA
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RE: I sense a great need
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by KB2VXA on May 5, 2005
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Hi all,
"The investigator told me that if I had stood under the pole, I would have heard the arcing."
Now what do you do when you're bracketed by two 13KV feeders each a block away? At night when it's quiet I can hear creepage on every insulator on every pole wherever those lines go. I can hear the "arcing" noise from 160M to 6M (and beyond when it's a particularly damp night, gets MUCH louder too) typically S5-7. This is common all along the shore, the closer to the water the worse it is so besides moving inland I believe nothing can be done about it. Sea spray and high voltage simply don't mix.
Hmmm, I guess if BPL comes to town I'll never notice. (;->)
73 de Sparky KB2VXA
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RE: I sense a great need
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by KG5JJ on May 21, 2005
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Another pathetic polluter; switching supply battery chargers. Neighbors' units make hamming almost impossible in my subdivision. Even idling, they produce garbage. Some are left on 24/7 during the winter months on marine batteries.
Solution:
Move. I'm looking for another home. No neighbors, no polluters.
These "unintentional radiators" should be banned. Offering brute-force AC chokes to the closest neighbors didn't fly. They have no problems, so, there are no problems. Besides, offering cures may land one in court, when little Johnny plays with matches, or big Johnny goes to sleep with a cigarette in hand and the house goes-up in flames.
73 KG5JJ (Mike)
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