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RFI - the continuing saga

archjeb

Active Member
Jan 26, 2014
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28
28
Folks,

Thanks on the other threads the suggestions for identifying and eliminating various RFI across various HF bands. I've significantly reduced my noise, especially with the use of mix 31 and mix 43 toroid chokes around problematic cables. Some really noisy switchers, I've replaced, etc.

But I have one noise source that appears to be utility power that I can't seem to get rid of.

On 40m I have noise at every 60Hz.As you can see in the spectrum scope there is noise at 7.120, 7.180, 7.240, etc.

40m-noise.jpeg

I'm assuming this is from utility power noise at 60hz.

I'm running the radio on an AGM battery and NOT running it off a power supply. If I disconnect the antenna, I get no noise...so this is coming in from either the antenna or feedline.

Any thoughts/suggestions?

Thanks,

-J
 

J: The noise is appearing at 60KHz...not 60 cycles(Hz)...The trick to running off battery is having the house electronics shut off...All Breakers turned OFF...then run off battery.
A repetitive noise source like this could be many things...Router/touch lamp/Christmas lights...I have seen this from Electric dryers/ Air purifiers, or anything with a fan and/or small motor....Night and Day is this???... or at some other irregular time interval?
Glad your making progress
Utility noise is normally constant All across the band and fairly constant level, though can spike in spots when an ark or pulse occurs.
All the Best
Gary

PS: if you remove the antenna connection and noise goes away...it's being picked up by the antenna and/or feedline.
 
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J: The noise is appearing at 60KHz...not 60 cycles(Hz)...The trick to running off battery is having the house electronics shut off...All Breakers turned OFF...then run off battery.
A repetitive noise source like this could be many things...Router/touch lamp/Christmas lights...I have seen this from Electric dryers/ Air purifiers, or anything with a fan and/or small motor....Night and Day is this???... or at some other irregular time interval?
Glad your making progress
Utility noise is normally constant All across the band and fairly constant level, though can spike in spots when an ark or pulse occurs.
All the Best
Gary

PS: if you remove the antenna connection and noise goes away...it's being picked up by the antenna and/or feedline.

oops, was looking at the wrong side of the decimal point :). Thanks Gary. It does appear to be coming in on the feedline because when I take an AM radio near the coax, I get noise.
 
Glad you finally found it, and I hope you didn't give the power company too much grief
Not at all. Guy came out and we chatted - nice fellow. He noted that the noise got worse by my house o_O and we just laughed.

There is some noise down by the power pole and down the road as I walk the lines. But we've come down from an S9 to around an S2 by just cleaning my noise up - which is an order of magnitude better. I'm below an S1-S0 on 160 meters. 160 was as noisy as the rest, but with all the filtering, its now quiet noise wise. Its really the HF bands that need a little more cleanup.

I'm just shocked about how much noise there is with off the shelf products. Until getting into HF, I had no idea how much noise there was out there and I'm still shocked that companies can sell products that emit so much noise. I thought there was FCC part 15 standards for this??

Thanks again everyone for the pointers. This truly has been a journey.

-J
 
Folks,

I found two more noise sources. A fan in the shop that is for ventilation. It creates a birdie every 27Khz. Any thoughts on how to filter this?

I also have another switcher for some networking equipment for a -48VDC equipment. It's creating a lot of hash.

I've tried to use multiple ferrite beads & #31mix toroids with multiple turns through the toroid, and even an inline AC filter on the supply side and its to no avail -- still have the noise.

Any suggestions? The fan I can try to replace since its old anyway. The DC48v powersupply is a little more challenging to replace.

Thanks

-J
 
So I've got a lot of the noise filtered now across the bands except one particular source that is very repeatable.

On 80/75meters I have noise every ~26Khz when I have the single circuit on going to the shop which is a LONG run - ~ 150'. Even with nothing turned on (unplugged) I get noise generated when that circuit at the breaker is turned on with no load on it.

So I'm theorizing that this long run is acting like a big antenna given its length and it must be some other noise induced on the house wiring. I was thinking about adding a toroid in the breaker panel for just that circuit and winding 12ga THHN around it about 10 turns. Any thoughts on doing this?

This is my last bit of noise I'd like to get cleaned up if possible.

I have some general noise from ethernet in the house; that is a different wide band noise that I'm trying to clean up too.

Thanks,

-J
 

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