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  #1 (permalink)  
Old 10-04-2015, 7:11 AM
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Default Interference up and down the HF bands

A friend of mine has asked for help trying to figure out where he is getting interference from on the HF bands. He has silent carriers all over the place. I asked him to write down where at and he did for me. He's called out cable companies, and the electric company, who all said "Not us". Here's some of the place's he's getting it, and the S-meter signal. It's not the radio, he get's it on a Yeasu, an old Heathkit, an a portable receiver.

14.072.75 S-5 _ 10.121.98 S-7 _ 7.277.48 S-7
14.121.00 S-6 _ 10.072.75 S-5 _ 7.229.29 S-6
14.169.20 S-6 _ 10.024.57 S-5 _ 7.205.11 S-7
14.217.40 S-5 _ 9.928.19 S-5 _ _ 7.181.10 S-7
14.265.60 S-5 _ 9.858.16 S-5 _ _ 7.084.75 S-6

Looking at the first column, the spacing is an even 48.2 KHz. The other two columns, the spacing does not seem to be uniform. He says he does not have any touch lamps in the house. He's tried using the portable receiver to snif it out, but it does not seem to be working well.

Any ideas what it could be, or an effective way or piece of equipment to sniff it out?
(sorry for the scrambled columns, it looks nice and lined up and spaced out when I'm editing it).

Last edited by Wyandotte; 10-04-2015 at 7:15 AM..
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Old 10-04-2015, 7:35 AM
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Step One is figuring out whether the source is outside his building.... or not. Using the battery powered portable receiver, tune in one of the carriers that is strong. First, if there are any uninterruptible power supplies for computers or alarm systems, shut them off. Did the noise go away? Next, go to the electrical service entrance main circuit breaker and shut the Main power off to the entire building. Did the noise go away? If so, you needn't look farther than somewhere in the building for the noise. You may want to start by taking the portable receiver and moving around the building to find where the interference is strongest. Remember to check on all the other frequencies you listed as well as the one you were on when the power was cut.
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Old 10-04-2015, 9:10 AM
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48KHz range is probably a switching power supply, I have a cheap replacement laptop supply that wreaks the HF band about every 48KHz. The easiest way to start looking for the problem is shut off the circuit breakers in the house one by one to see if the noise goes away as mentioned above. If it does then unplug appliances in the room or circuit that was affected until you find the specific item thats making the noise.

If the noise is not affected by any breakers in your house then its coming from somewhere else and that takes a directional antenna and a portable receiver to continue the search. At that point your chances of finding it are seriously reduced.

A small loop antenna and spectrum analyzer or portable HF receiver is best for trying to pinpoint the source and a loop will be most directional going for a null in signal rather than a peak. Its very difficult and frustrating trying to pinpoint a signal source with just a receiver and whip and without a directional antenna you may never find it. Even with the proper equipment you may never find it because you won't have access to the building or area causing the interference.

If its coming from outside your house and you can at least pinpoint it to a specific house or building, hopefully you can get the owner to cooperate and shut off breakers one by one to rule out their property or ID the room that is making the noise.
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Old 10-04-2015, 11:39 AM
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Thanks to prcguy for describing the "next steps" if you discover the RFI / EMI source is inside your building when you kill the main power as I suggested. If interference disappears, then the next logical step is to restore power and being the breaker-by-breaker switch off and search process.
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Old 10-05-2015, 11:48 AM
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Default Thanx

Thanks for the suggestions. I'm printing them all out and going over there this weekend.
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Old 10-05-2015, 5:44 PM
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Default Has he removed the antenna

from the receiver and see if the silent carriers are still there?
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Old 10-31-2015, 10:20 PM
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Have to rule out the building first before calling utility companies. Most all the noises we get are generated by ourselves. TV sets, every switch mode power supply (everything these days, computer monitors, ethernet routers, printers, cell phone chargers, and on and on), computers, monitors, ethernet wiring, and any number of things can cause trouble. Just go around unplugging things, turning off breakers, kill all the power and use the radio on a battery. It'll be found.

Now then, one interesting thing is the spacing. I have seen (and in fact am plagued with) a computer sound card sampling clock radiate a lot of energy on the wires plugged into it. Often you see numerous strong peaks across vast ranges of radio spectrum. The peaks can sometimes seem to be modulated, having a sideband. They are typically separated by and appear at multiples of the clock. Changing the sample rate of the card will cause them all to shift. Don't expect them to appear exactly where you think they should be. Most consumer class cards and even some pro ones do not have an accurate sample rate clock.

My old Harman Kardon digital path receiver radiated RF at numerous frequencies on the speaker wires. The wall-wart that came with my Baofeng hand held radiates wide band hash into the power line. D-Link gigabit router radiated lots of hash at various places on HF. Netgear replacement doesn't, it's mostly quiet. No, it wasn't the power supply. D-Link is known to cause that.
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Old 10-31-2015, 11:45 PM
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the Baofeng wall wart is horribly noisey
i am surrounded by switchers
and my big kid has a 55" plasma tv! that thing makes my teeth buzzzzz
even the cheap harbor freight battery maintainers are hugely noisy switchers
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Old 11-01-2015, 7:48 AM
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When doing the breaker off/on thing, be aware that you may have multiple devices causing problems.Quick and dirty - turn off the main breaker and any UPS/battery operated devices. If the noise went away then turn off each individual breaker, then turn on the main breaker and start turning on the individual breakers until the noise reappears. You have now found a circuit feeding a noisey device. Turn this breaker off and continue with the rest of the breakers one at a time to verify each is clean. Since you have 3 different HF ranges you may have 3 different problem devices. Good luck and let us know what you find.
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Old 11-01-2015, 1:53 PM
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Default interference

switching power supply, plasma tv, halogen lights, wireless alarms.grow lights, long range radar . also street lights, solar controllers ,ect.
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Old 11-01-2015, 3:09 PM
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Not forgetting the scourge of BPL which is growing world wide especially in country areas where we moved to, to escape the electrical noise of the city. I may turn into a rebel and start blowing up power pylons if they come round my way.....
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Old 11-01-2015, 3:58 PM
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Grow lights?
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Old 11-01-2015, 4:20 PM
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Default interference

yes grow lights. I know a ham that lives Hollywood. His neighbor grows plants inside and the noise is bad.The power company came to his home many times and has not been able to help him.
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Old 11-01-2015, 4:25 PM
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if there is interference to a licensed radio amateur that is not being addressed by the normal channels
the the ARRL will work with the ham and the FCC to get stuff fixed
and they have a darn good track record with success
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Old 01-30-2016, 8:43 PM
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So, was the source found? It would have been nice to know the cause.

Upon reading this thread, I know that the new Smart Meters tend to cause burst of energy that can drive a person crazy figuring out that being a source.
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