Audible electric spikes in system

[Speedskater]

This is a blog from a guy who spends a lot of time chasing this type of problem:

EMI - RFI page

It's best to solve pop problems at the source.

[zulusound]

You mean, chop down my neighbor's antennae?

Originally Posted by Speedskater

This is a blog from a guy who spends a lot of time chasing this type of problem:

EMI - RFI page

It's best to solve pop problems at the source.

[brianroth]

If the neighbor is a ham (vs a CB'er...a whole different mindset), he probably would be helpful in determining if the noise is coming from his setup. Hams tend to have a good attitude about that sort of thing, vs CBers.

Bri

[Speedskater]

Like Brian wrote, if the guy is a real HAM, he will be a good source of help. Don't start suggesting that it's his fault, just ask him for help with your problem.

[Lotus 7]

Your noise pulse looks like it may very well be a RF pulse being picked up at an input. It's a differentiated pulse with of 560 mS duration with clear 120 Hz modulation. If it's RFI from your neighbor's transmitter, it's possible it's being picked up on a mic input, a line input (through the transmitted signal), or even through your power line, although the PL-8 has very good RFI filtering so that is unlikely. You may need to try to isolate the path that the noise is entering your system.

The shape is characteristic of a rectified RF pulse. The leading edge is differentiated, then the 120Hz modulation appears, and then the trailing edge is again differentiated.

Does the level of the noise pulse change when you change mic gain?
Does it reduce if you drop your master gain ?

If it's unaffected by the gain settings, it may be getting in directly to your recording interface or even your computer.

It's always possible that it has nothing to do with your neighbor and may be power line related. It's clearly a "square" pulse of something. Have you noticed any light dimming or flickering during the pulse" Maybe try sticking a voltmeter on the power line and look for a line voltage fluctuation when a noise pulse occurs. At more than a half second duration, it would show on any analog voltmeter and on many digital meters.

Good Luck!!

Noise pulse waveform below:

[Richard Crowley]

It doesn't sound particularly like anything you could expect from RFI interference from a ham transmitter. I would bet against the ham being the source. But in any case, most hams should be helpful in discovering the source (and remedy) whether it is them or something else. In the even that he is not helpful, contact the local ham organization for help from his peers.

Richard
KE7GKP

[brianroth]

I am glad that Richard chimed in here, since hams are often falsely accused of causing RFI problems.

Most hams are concerned about any interference they MIGHT cause to a neighbor.

If a ham radio system is running according to specs as defined by the FCC (most are!) and a neighbor is having problems, they often attempt to solve the problem as a "good neighbor".

Bear in mind...if a licensed transmitter nearby YOUR house is running correctly, yet you have RFI probs in your system, the actual problem is YOURS.

FCC part 15 clearly declares that electronic equipment "has to accept" any RFI crapola that rolls in as long as the transmission system meets FCC regs.

EXAMPLE: I've lost track of how many "pro" recording desks get "warbles" from cell phones located in the same room.

As for detecting where the noise comes from....

Use an old, battery powered analog AM radio tuned to the low end of the band...530 to 700 kHz where there are no audible signals....and see/listen to what's there.

Use something like a OneAC line viewer and an oscilloscope to see what stuff is on the mains.

Bri

[Speedskater]

Jim Brown being both a HAM and the AES Committee Chair on EMI/RFI has many papers on the interference problem.

Audio Systems Group, Inc. Publications

[zulusound]

Hey, thanks everybody for chiming in. I'm open to everything that it could be- my fridge turning on or anything.... as I said in my original post it affects my whole house and I can hear it through all speakers in my house, such as a boom box in a bathroom.

The thing that makes me a bit suspicious that it's my neighbor (I have asked him before and he said there is "no way" it could be his equipment), is the pops seem to happen only on weekends and start in the afternoon after he comes home from work.

[zulusound]

Hi Lotus,
Thanks for your efforts in your response.
I have not noticed lights dimming, and I don't believe changing gain will affect the level of click/ pop that is captured. It affects all the outlets of my house. I have tried looking at my volt meter on one of my UPS units but they are fleeting and I haven't timed it well. They happen mostly on the weekends and late afternoons.

Originally Posted by Lotus 7

Your noise pulse looks like it may very well be a RF pulse being picked up at an input. It's a differentiated pulse with of 560 mS duration with clear 120 Hz modulation. If it's RFI from your neighbor's transmitter, it's possible it's being picked up on a mic input, a line input (through the transmitted signal), or even through your power line, although the PL-8 has very good RFI filtering so that is unlikely. You may need to try to isolate the path that the noise is entering your system.

The shape is characteristic of a rectified RF pulse. The leading edge is differentiated, then the 120Hz modulation appears, and then the trailing edge is again differentiated.

Does the level of the noise pulse change when you change mic gain?
Does it reduce if you drop your master gain ?

If it's unaffected by the gain settings, it may be getting in directly to your recording interface or even your computer.

It's always possible that it has nothing to do with your neighbor and may be power line related. It's clearly a "square" pulse of something. Have you noticed any light dimming or flickering during the pulse" Maybe try sticking a voltmeter on the power line and look for a line voltage fluctuation when a noise pulse occurs. At more than a half second duration, it would show on any analog voltmeter and on many digital meters.

Good Luck!!

Noise pulse waveform below:

[Richard Crowley]

It COULD still be your neighbor. Maybe he has an arc welder in his garage. Or an electric-fired Bessemer converter in the basement? But it doesn't sound like the kind of RFI you would hear from a communication transmitter (CW, AM, FM, SSB, or even digital).

I agree that a better approach would be to ask for help IDENTIFYING the problem than jumping to the conclusion that he is CAUSING it with his transmitter(s).

[zulusound]

My neighbor is a hard person to approach, and I'm not sure it's him or his gear, anyway. The reason it might be, is that I don't ever remember hearing the spikes the hours he is away from home at work.

I might just invest in a balanced power system and see if this quashes it. I wonder if there a way to clean up the spikes at my panel before they come into my house at all.

Originally Posted by rcrowley

It COULD still be your neighbor. Maybe he has an arc welder in his garage. Or an electric-fired Bessemer converter in the basement? But it doesn't sound like the kind of RFI you would hear from a communication transmitter (CW, AM, FM, SSB, or even digital).

I agree that a better approach would be to ask for help IDENTIFYING the problem than jumping to the conclusion that he is CAUSING it with his transmitter(s).

[Speedskater]

Why would you think that balanced AC power would cure an interference problem?

[Lotus 7]

This is really a hard one because of the very low occurrence rate, and the strange pulse character.

If it were a regular RF transmission, as rcrowley said, it would look and sound entirely different (and would be occurring much more often). The pulse shape looks like it's almost a square DC transient because of the fast rise and fall and the AC coupling recovery that's visible in the waveshape. The 120 Hz hum on top adds to the puzzle. The "hum" sounds clean (not like the random noise of an arcing motor brush or contactor. Then it stops with a clean, square edge. The approximately half-second duration is in the range of the start up timing for a large electric motor that uses a start winding and a centrifugal start switch. However, "square DC transients" can be caused by rectified strong CW (Continuous Wave) RF pulses.

Since you can hear it on your boom box and stereo it sounds like it's being carried on the power line, but may also be radiated. You might try listening for the "pop" on a battery powered portable radio to determine if it's radiated or being conducted in through the power supply.

Again, although it's obviously a real PITA, if it were me, I'd try to start disconnecting pieces of gear and trying to find exactly where it's getting into your audio chain. If it doesn't change level with changes in your master level faders, it's probably getting in somewhere near the output end of the analog audio chain or your interface. Finding out exactly where might point you to a possibility of a solution.

Sorry we can't be more helpful.

[apprenticemart2]

Have you got an outside security light with PIR that switches on/off automatically, what have you got/or a neighbour that gets switched on and off when there's people around ie evenings/weekends? Could it be a dodgy relay of some sort? Have you got a bulk milk tank in your basement that stirs the milk every 20mins after evening milking?

[brianroth]

Going back through my previous comments.....

1. Use a battery powered analog radio that can receive the AM broadcast band, and listen at the "low end" of the band (say, 530 to 640 kHz) where there are no audible radio stations. See what noises you can hear there. Years ago, I discovered that an outdoor "security" light on the side of a studio was "struggling" to come on during the day due to a defective photocell AND a faulty HID lamp inside of the fixture. The fault introduced a VERY odd audible "hash" into some of the studio's equipment. I found it by listening to the low end of my truck's (analog) AM radio band, and then walking around the building, where I spotted the defective security light fixture.

2. Since I am a test gear junkie, I bought one of these awhile back:

http://www.gryphon-inc.com/Spec%20Sh...%20ONEView.pdf

It lets me "look" at the AC mains via my Tek scope to see what sort of garbage is there on the line.

Bri

[zulusound]

Thanks, Bri. I haven't heard the pops/ clicks for a couple weeks, but I think I will buy a battery powered AM radio and walk around my house next time it happens. If it was less intermittent it would sure be easier to diagnose! It happens more often on the weekends so maybe it'll happen today.

[LeeYoo]

Hi all.
I am thinking "automatic antenna tuner".
Because of the relative long duration and frequent intervals.
Spikes from fridges etc. are short and welding etc. is long.
Keep a log of the exact times.
Talk to the man.
Leo..

[zulusound]

Well, I don't have a session today, I have been waiting for the spikes, but of course they are not happening today (the spikes usually happen on weekends). Hard to track down the issue when it's so infrequent. But I have to say it ruins plenty of takes when I do have a session going and it's spiking. And that's not the time I can say to people, hold on, after we re-do your last perfect vocal take I'm going to walk around my block with an AM radio. Then we'll re-track that part.

Originally Posted by LeeYoo

Hi all.
I am thinking "automatic antenna tuner".
Because of the relative long duration and frequent intervals.
Spikes from fridges etc. are short and welding etc. is long.
Keep a log of the exact times.
Talk to the man.
Leo..