Strange interference pattern on 40 Meters and below.

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  • Updated 3 years ago
It is Saturday morning about 8:30 a.m. EDT.
I have been having this very strange cyclical interference on 40 Meters.
I tuned below 40 an the pattern got a bit stronger.
It sounds like some kind of motor driven source.  
So far, I have not been able to locate or identify it.

Any suggestions?  Pool pump?  Sump Pump? Neighbor's freezer going bad?

Ken - NM9P
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Ken - NM9P, Elmer

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  • baffled

Posted 3 years ago

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Jim Gilliam

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Maybe it's some form of over-the-horizon radar. I see crap like that on 75 meters in the morning.

Jim, K6QE

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Ed, K0KC

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When my XYL is using the treadmill, 40 meters and below is  unusable. I guess I would be better off if I spent more time on the treadmill rather than on my 6700...then I would not have to worry about interference on 40 meters!

Ed, K0KC
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Ken - NM9P, Elmer

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You and me both, brother!
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Hi Ken,
I'm about 90 miles W/SW of you and it's all quiet over here at 14:15:00Z. Most likely something local, as you suspect. 40M is a little strange this morning..close in stations (<200 miles) are difficult to copy, but stations further out are strong. Sorry I couldn't help more. FYI, I'm using a 6500 and a dipole.
73, Dave
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Danny K5CG

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The wide band nature and the buzzing background noise sounding like it might be 60 Hz along with the noise floor bouncing around with it makes me think it's localized near you and related to some appliance or AC mains powered object like a switching power supply, or umm a treadmill.
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Danny K5CG

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Try shutting off the main breaker to you home and see if it goes away (put the radio on batt).
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James Del Principe

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From wall warts to solar panel inverters, the problem will only get worse over time. More equipment becomes "electronic" like my washer and dryer that wipe me right off the air. Dimmers, some CFL and even LED bulbs can be sources of interference.   Hopefully, the better manufacturers will be responsive to complaints.    Jim
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EA4GLI - 8P9EH - Salvador

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Water pump or elevator motor.
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K1UO - Larry

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since it "cycles" maybe something like an aquarium heater....
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Ken K7YR

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GE Ken

I have nearly the same interference on 75 meters, I have never checked 40.  It comes from our GE washing machine computer controller.  As the machine changes cycles so does the interference.  -40 ~ 45 DBm from the machine located in another building some 120 feet away. 

On a second front, I was plagued by another interference caused by a treadmill located some 1,200 feet from my home.  That interference was showing as -40 DBm raspy pulses around 50 KHz apart, while they were kind of steady, they did move around some.  Even if the treadmill was turned off the power supply / computer radiated this interference.  S-9 + 60 db over 9 in their driveway.  They agreed to unplug it when not in use......Worked for me, no further issues

The Chelan County PUD is excellent in responding to RFI.  As this is an agricultural area, Apples and cherries, the loss of a transformer, line, and equipment during the hot summer months during irrigation season is not acceptable and every and any potential noise issue is researched and put to bed asap.

Good Luck.

Ken K7YR