Author Topic: Interference and Noise (Read 94616 times)

Cutty Sark Sailor · « **Reply #75 on:** April 15, 2014, 06:14:04 AM »

Quote from: Dr Obbins on April 15, 2014, 04:22:38 AM

I woke up at 1:00am with one of those "Duh " moments. The pet fence has a adjustment knob on it. I turned it down from 7 to 5 and while the noise is still there, it was greatly reduced. The collar will still work, just not quite as far from the buried wire as before. My wife was wondering why I was running up and down the steps from the basement to the 2nd floor in the middle of the night. LOL

My spouse has become used to all the "run and adjust" "run and observer"..RaA, RaO, RaA, RaO... between lightning and cameras, etc... . They seem to learn to accept it after awhile... especially running through the house and yard with am radios and EMI meters trying to find sources of EMI, and that exact camera adjustment etc,.. . Usually about all she'll say is "while you're out there, will you put feed in the bird feeders?"...

Dr Obbins · « **Reply #76 on:** April 15, 2014, 08:46:25 PM »

Over the weekend, I was able to set the unit so it was in the 90+ efficiency long range. Then in the evening, it went into interference mode. With the house to my self tonight, I did a little researching into interference sources.

First with the pet fence turned down a pinch and nobody home all day, it was consistently reading in the 45% EL range. We have recessed lighting through the house and in the kitchen, there are 10 screw in florescent bulbs. With all 10 on, there was not any noticeable interference. Then the microwave was turned on and had a large impact. Also the light dimmers wreak havoc.

So the question is, is here a way to balance good reception and still live in the house? If the gain is turned down enough not to go into interference mode, the station stays in the 15% EL range. Is there another adjustment that should be considered?

Dr Obbins · « **Reply #77 on:** April 16, 2014, 08:38:35 PM »

Today I called the manufacturer of the light dimmers and explained the issue with the dimmers creating interference. To make a long conversation short - he said that I had to choose between using the dimmers or the lightning detector. At lunch I went out and purchased 3 non dimming light switches.

Cutty Sark Sailor · « **Reply #78 on:** April 18, 2014, 06:10:56 AM »

Lots of new Kits being built. Let me call this to your attention... it may happen:
When you connect the controller ground wire to the ground block, it is just possible that the torque from tightening the connector will snap the pin going through the circuit board... this nearly drove me nuts with intermittent high levels of noise.

I then placed a tiny drop of hot glue on the base of the replacement

So if you've got a noise issue, you might go back and check that...
I think the same thing could be possible with the antenna connection terminal block, though with 4 pins the twisting would be lessened.

Mike

DaleReid · « **Reply #79 on:** April 19, 2014, 10:41:35 AM »

How are you guys grabbing images of the signal level that you're showing?

I am running FireFox and when this signal tracing is displayed, when I right click and view or save the image, I get a grey block that has none of the info in it.

Is there another routine or app that I can get to ride on the top of firefox to grab those images?

Dale

Dr Obbins · « **Reply #80 on:** April 19, 2014, 10:48:49 AM »

I hit the "Print Screen" button real quick.

Cutty Sark Sailor · « **Reply #81 on:** April 19, 2014, 11:21:30 AM »

I import screen capture into one of my versions of Paint Shop Pro, crop it there, etc.... The image you see on your web interface is a 'fake' image... server generated.

miraculon · « **Reply #82 on:** April 19, 2014, 07:46:47 PM »

I have been pleasantly surprised about the electrical environment here in Rogers City, MI. I took my RED lash-up down for permanent installation, and got the old "green" ( USB 6.8 ) up and running. I have the "green" jumpers set to maximum gain without interference mode. RED was working well in the temporary setup in an upstairs bedroom, with higher gain than in my Livonia, MI home.

I have the threshold set to the default (same as the original fixed values) for now, but I was experimenting with much lower thresholds at the high gain.

I'll get RED back up and running in a few days. I am hoping for good results, since I used the "green" amplifier/antennas with a 9V battery and headphone to sniff out noises. I am installing both detectors in a detached garage, with a wireless client connecting to my Wireless Access Point.

Apparently my neighbors don't own a plasma TV.. $\:D/$

Greg

Dr Obbins · « **Reply #83 on:** April 30, 2014, 03:42:48 AM »

Any ideas what this might be. It is currently showing up at 2:30am with no activity in our house or either of the 2 neighbors. I live way out in the country. No street lights, no HVAC running, nothing at all going on around here.

It is not a brief event, but one that is showing up many times and stays on the screen for up to 30 seconds.

Cutty Sark Sailor · « **Reply #84 on:** April 30, 2014, 09:30:33 AM »

Quote from: Dr Obbins on April 30, 2014, 03:42:48 AM

Any ideas what this might be. It is currently showing up at 2:30am with no activity in our house or either of the 2 neighbors. I live way out in the country. No street lights, no HVAC running, nothing at all going on around here.
It is not a brief event, but one that is showing up many times and stays on the screen for up to 30 seconds.

With your a channel gain set so low it's hard to tell, but it's showing only on the b channel, so it's directivity is at right angles to that antenna which might help locate. When it's occurring, this link will show you your signals and frequency spectrum:
(link removed - shared privately) (2.5 second sampling)
(easier for me to do, and probably less confusing for now... let me know when/if you want the page down....)

Mike

Dr Obbins · « **Reply #85 on:** April 30, 2014, 09:34:25 PM »

Interesting info.

This weekend I will have to go back to the attic and see which antenna is facing which direction and then analize the data being presented. The Direction Indication looks useful also. Please leave the page up for a bit.

Cutty Sark Sailor · « **Reply #86 on:** April 30, 2014, 09:55:50 PM »

Quote from: Dr Obbins on April 30, 2014, 09:34:25 PM

Interesting info. This weekend I will have to go back to the attic and see which antenna is facing which direction and then analize the data being presented. The Direction Indication looks useful also. Please leave the page up for a bit.

Well, don't put a whole lot of 'faith' in being able to determine 'direction', because of the way the signals are received and processed, it's more of a 'fun' experimental thought, although it does have its uses and value at times, with a lot of practice.

Mike

miraculon · « **Reply #87 on:** May 07, 2014, 10:25:54 PM »

It looks like we need to replace the furnace in the house, so we have it shut down due to fumes and incomplete combustion. To take the chill off, I bought a "Vornado" heater with thermostatic control. I noticed in the "participants" list that #668 was offline. I checked the output web page and it is into interference mode. The Vornado is the cause of this, when I turn off the heater the station immediately comes out of interference mode. Turn it back on, interference mode. A-B-A test.

Strangely enough, the 6.8USB antennas (ferrite rod) are out in the garage and the heater is in the family room area at the rear of the house. I did have my threshold adjusted a little lower than normal, but the noise looks like it would exceed the default threshold as well.

It has a continuous motor control, so I expect that it is the culprit. I tried a clamp on ferrite to no avail. I'll attach the waveform shown in the screen-shot of the tracker.

UPDATE: This thing is going back to the store. It wipes out AM reception all over the house with a loud buzz. Again, I can make it come and go with the heater power switch.

Greg

miraculon · « **Reply #88 on:** May 08, 2014, 10:21:58 AM »

Quote from: dfroula on March 17, 2014, 09:25:30 AM

I took some additional oscilloscope measurements that verified the effectiveness of the choke in attenuating the noise. Updated report at link:

http://projectmf.homelinux.com/station_pics/Harmonic_Distortion_EMI.pdf

Don

I may be utilizing these fixes, since I am replacing my furnace. We'll see how it goes and if it is a big problem. That portable Vornado heater was obliterating the AM band and causing reduced gain on RED and on the "Green" it was in constant interference mode that could not be eliminated with the threshold control. If this is the "baby brother" of the furnace one, I am in for some headaches....

Greg

dfroula · « **Reply #89 on:** May 08, 2014, 11:38:43 PM »

The culprit is the variable speed DC blower and/or inducer motors in the furnace. The choke has continued to be very effective in attenuating the noise from the blower.

My inducer motor is a standard shaded-pole job, so doesn't contribute to the issue.

Don
WD9DMP

miraculon · « **Reply #90 on:** May 09, 2014, 10:12:37 AM »

Don,

Do you have the manufacturer, part number and inductance value of the PFC choke?
I found this York article that has filter kits. I will need to see how many fractional HP the motor is before I order one.
http://yorkcentraltechtalk.wordpress.com/2011/09/26/pf-choke-for-ecm-motors/
What do you think about getting one of these kits (appropriate to the motor size)?

Greg

miraculon · « **Reply #91 on:** May 14, 2014, 06:49:04 PM »

Good news. The new furnace isn't causing any interference mode problems. I can watch it before, during and after the furnace running and I don't see any change in the waveforms on both the "green" and RED detectors.

Greg

dfroula · « **Reply #92 on:** May 14, 2014, 08:07:24 PM »

Greg,

Good deal. Hopefully, they integrated the chokes into the motor!

The noise I was seeing in the controller signal display was subtle - just a small bump in the noise floor. It took an oscilloscope connected to the test outputs of the amp to spot the very narrow spike on positive and negative peaks of the AC waveform. It was so narrow, that sometimes the auto-noise floor reacted to it, sometimes not.

I just saw your request for info on my choke. Genteeq never gave me a precise value. The choke was made by Tyco, with a GE part number. The engineer said it was old stock from before Genteeq bought the motor division from GE. I can get the numbers if you like, but I plugged them into Google and found nothing.

Regards,

Don
WD9DMP

miraculon · « **Reply #93 on:** May 14, 2014, 08:36:03 PM »

Quote from: dfroula on May 14, 2014, 08:07:24 PM

Greg,

Good deal. Hopefully, they integrated the chokes into the motor!

The noise I was seeing in the controller signal display was subtle - just a small bump in the noise floor. It took an oscilloscope connected to the test outputs of the amp to spot the very narrow spike on positive and negative peaks of the AC waveform. It was so narrow, that sometimes the auto-noise floor reacted to it, sometimes not.

I just saw your request for info on my choke. Genteeq never gave me a precise value. The choke was made by Tyco, with a GE part number. The engineer said it was old stock from before Genteeq bought the motor division from GE. I can get the numbers if you like, but I plugged them into Google and found nothing.

Regards,

Don
WD9DMP

Thanks, Don. It looks like it is moot point since the motor is quiet. The "Vornado" experience had me nervous. Fortunately, they took that space heater back and I got an old-fashioned type. It looks like the Carrier/Payne (my new furnace) folks actually know how to spell "EMC"...

Greg

DaleReid · « **Reply #94 on:** May 14, 2014, 09:24:48 PM »

Speaking of noise clamps, are there sources for good clamp-around ferrites that one can snap over the power cords going from the USB supply to the controller, or around the various CAT 5 coming in, too?

I had some a few years ago that were rings and you had to wind stuff through them, then once while trying to reduce feedback in a radio intercom installation in a fiberglass homebuilt aircraft, we had some that were sort of slip and you just snapped the holder around the wire. I'm not sure where those came from, or if it was even worth applying them to see if noise is cut down further.

miraculon · « **Reply #95 on:** May 15, 2014, 08:14:42 AM »

They certainly make them. I have used them, with mixed results. Sometimes they help, sometimes not.
Intermark USA has some low frequency versions. Most of the ferrites are effective in the 100's of MHz, which is not what we need for the Blitzortung system.

Here is the link to the Intermark LF ferrites. http://intermark-usa.com/products/emc/emi-ferrite-emi-ferrite-cores/low-frequency-khz-ferrite-cores/

I think that TDK has some too. Mouser sells the TDK ZCAT series. http://www.mouser.com/Passive-Components/EMI-RFI-Components/EMI-RFI-Suppressors-Ferrites/Ferrite-Clamp-On-Cores/_/N-bw7t7/

Try eBay, there are some sellers there.

Greg

dfroula · « **Reply #96 on:** May 15, 2014, 08:37:19 AM »

I tried some Radio Shack snap-on ferrite chokes on the USB power leads, but noticed no effect. As Greg mentioned, they work well at VHF/UHF frequencies, but do little at the high-audio frequencies we are concerned with.

You might be able to find some ferrite torroids of appropriate material and wind the power cord through those. I would think you would want high-permeability (2000u) to be most effective - the same stuff the antenna ferrite rods are made of.

Regards,

Don
WD9DMP

Quote from: DaleReid on May 14, 2014, 09:24:48 PM

Speaking of noise clamps, are there sources for good clamp-around ferrites that one can snap over the power cords going from the USB supply to the controller, or around the various CAT 5 coming in, too?

I had some a few years ago that were rings and you had to wind stuff through them, then once while trying to reduce feedback in a radio intercom installation in a fiberglass homebuilt aircraft, we had some that were sort of slip and you just snapped the holder around the wire. I'm not sure where those came from, or if it was even worth applying them to see if noise is cut down further.

DaleReid · « **Reply #97 on:** May 15, 2014, 01:14:55 PM »

What if I take a ferrite rod and wrap the power line from the wall wart to the USB plug around it a few times, right near the board? Exercise in futility or maybe worth a try? Just thinking. I have a lot of those rods...

dfroula · « **Reply #98 on:** May 15, 2014, 03:06:39 PM »

Worth a try. Toroids are nice because they are self-shielding, but the rods should work in this application. Put a few in a bundle....

Don
WD9DMP

Cutty Sark Sailor · « **Reply #99 on:** May 30, 2014, 09:36:58 AM »

Many of you who've ordered E field kits, and have had issues with interference on the H field location are going to be pleasantly surprised.
I had determined my environment was heavily H field noise, with little or no E field issues, but was still a bit concerned, being who and what I am.
Some of my EMI is 'seasonal', so the jury is still out on what the environment will be like come cold weather, but the E Probe picks up little or none of the signals from nearby Axle plant that causes issues with my N/S H field. Also no plasma TV, believe it or not, from next door, and little or nothing from the same vapor lights that periodically mess with H field.
What E field does have is high gain. Experiments show it exceeds the H-field in many respects, so Interference mode comes simply from too dang many signals exceeding threshold.

With 5 channels running, instead of 2, it can be tricky to see where any interference is coming from. However, I've learned it's almost never related to the E field probe, and almost always due to my A amp Ch1, (the N/S aimed at the axle factory ferrite

)

The point is, I think, that if you've had issues with H field reception, you may do a lot better adding E field.

Cheers!

News:

Author Topic: Interference and Noise (Read 94616 times)