The AM Forum

I have recently had an awful load of RFI show up at the shack. I can hear it from the BC band all the way to 10 meters. It peaks at about 2.087 MCS where it is 20 over. On 20 meters it sounds more like a white noise but is S-6

It is 24/7 and stays the same in signal strength. It sounds like power line noise but I did not think I would see the various peaks. I have been able to shut off all power in the house (except shack) so far with no impact.

Before I start signal hunting and possibly talking with neighbors, does anyone recognize this pattern?
Thanks,
Carl
WA1KPD

I had a problem like that once and turned out to be the neighbor across the street. 1 phase connection at the peak of the house was loose. Power Co fixed it when they went 1/2 dark.

Is that 120 KHz spacing between each pair of pulses? Any chance you could post a short MP3 audio file of what it sounds like Carl?

I had a problem with my QS1R when I first fired it up that was similar. It turned out to be the PC suck-ply was bad. I replaced with an EMI suck-ply and the problem went away. I would try that first before pestering your neighbors  ;).

Mike

Gotta new one in the hood here in Springtucky, Orygun. Sounds like two or more BC stations are being mixed/detected by something. 40 dog biscuits @ 3.870 MHz on the R-390/A. About 2 dozen or more harmonic in the ham bands up to 10 meters.

Wonder if the new HD stuff is causing RFI?

Craig,

Mike,
You have a QSR1, Good Man
The exciter should be cool.
I run a modified MRI amp on my HPSDR set up.
Pair of MRF150s in the final. I modified an erbteck board that cost me $69 for a 3 stage amp P-P FETs. works 160 through 6.  PM me if you decide to go that way and I can provide the mods. CTR Surplus sells the MRI amps.
W1VD and I have modified these boards. Very nice stuff.

Streetlight? It doesnt have to be on. A neighbors light also a suspect.

Carl

Thanks guys for the help.

Here it is. It is recorded on one of the peaks, but it sounds no different no matter where you are.

No street lights within a good 1/2 mile and all power in the area is underground. I have always had some sort of nose that seems to carry in on the underground feed for the poweline, but never this bad.

I am wondering if it was something that changed during the hurricane- we were out of power for a week. But since I have not been in the shack much I really cannot say when it got this bad.

Yes, I am dabbling in SDR now. Phil's support is top notch, and its a great product.
I can't wait for the exciter and the front end filter board. Surplus ripoff of Neb. also has 200 watt amps with a heat sink and basic control circuitry, but I will be interested in what you have.

Comparing the qs1r to an r390a is night and day. The r390 sounds good untill battle mode, the qs1r far surpasses in featrures and options once in battle mode. I won't go back to any othe rx.

Mike

That sounds like TV video. Horizontal pulse.
Any surveillance systems nearby? We tracked down a real strange problem from a TV antenna amplifier power supply emitting something similar to this noise.
You might try to find the strongest receive frequency with the SDR and get a portable receiver and start driving around, watching or listening for an increase in signal strength.

A router or rooter ( home computer )network could cause this problem near 20M also
Fred

Doesn't sound like power line noise,  more like something running, could be almost anything.  Check your QTH by using a portable receiver outside and then shut off everything including all your electronics in the shack.  This is what you should start with.

Fred

For what it's worth that is 60 cps pulse noise. I took your wav file and cut it down to .1 seconds and it neatly shows 6 cycles of pulse noise. It sure is ratty sounding. Hope you can locate it quickly. I would not hesitate to call your local utility company for assistance if the source is not readily located with a portable receiver.

It kind of looks like it, too. Do you have a neighbor with a plasma TV? Some of them are prolific RFI generators.

Cell phone charger?  Something like that?

Just listened to the wav file, sounds like what my backyard neighbor has in their house. Gud luck!

Craig,

sounds similar to the noise I had here. determined it to be a neighbors plasma TV. 

Carl, can you pick it up on your vehicles AM radio when tuned to 1700?  Drive by your QTH with your radio tuned to the upper end of the AM dial. You may be able to localize it.  That's how figured out where my noise was coming from.

Lots of harmonics. The 60 Hz reps drop out at the higher freqs leaving just 120 Hz bands. It's doesn't sound like some of the switching supplies I've heard.

If it is a plasma tv you are probably going to have difficulty.  I understand with them it is the screen itself that does the radiating.  Try telling someone he can't use his $2000 tv anymore.  you are going to have to come up with an antenna or rx network that nulls the source.  OTOH I think you said it is there all the time.  If true, that rules out a tv set unless the viewers are so brain fried they have the set on night and day all the time  ::)  I wonder if it is something like that AT&T Uverse.

With plasma TVs, the noise changes as the scenes change.  My nieghbor had a cordless drill charger that made constant noise like this...

CTR Surplus has a web site and sells on epay. I've bought a bunch of stuff from them. John usually has some MRI boards kicking around. You do need to mount the board on a bigger heat sink so it takes some work. The board is a foot square but I cut off all the control stuff and build a little bias module.
I have all the mods and pictures if you want to go that way I can send them to you. I need to put a 16 dB pad on the output of my 1/2 watt exciter to get the right drive. I also have schematics. I also have a pair of 1200 watt modules I hope to build into a linear someday.

I had similiar noise a few weeks ago and it was an old color TV that my daughter had hooked up radiating broadband garbage via the coaxial hookup.  One heterodyne was 1.882 with blips and burps high and low throughout the bands. Made good target practice.
Darrell KF4DX

Hello All!

     Sounds to me like one of the neighbors is growing pot to me.

    Tnx,

Having attempted to practice Ham Radio in Santa Cruz Mountains, I have firsthand knowledge of dealing with the growers and their ballasts.

That's NOT a ballast noise.  The digital ballast noise will go almost to 6 meters....  I detected it into the mid 40 mhz range.
 
Was interesting when I'd knock on the door.  "Hi, your digital light ballasts for your marijuana grow are causing me problems with my licensed transmissions".......

One showed me their prescription.  The others just shut the doors.

You can get radiation from the different kinds of bulbs they use if they aren't screwed in all the way, too...  But, I've not heard anything like the noise your .wav is when dealing with the growers.

TV maybe?  Bad utility connection somewhere?  Time to get the AM radio out.

--Shane
KD6VXI

See if anyone installed an automotive battery charger nearby.  Last winter I turned the receiver on one day and >60 over 9 noise/buzz.  I couldn't hear anything but noise up through 6 meters.  Got out the portable and found the noise next door, about 30' from my antennas.  He'd bought a cheapie battery charger for his boat battery.  He apologized for causing the noise.  I offered to buy him a better one, but he said he would put it on a timer, and run it after 2AM.  He did and no more problem.  But to date, that's the worst noise generator to affect me so far.   Runner ups were a floodlight with a built in photocell, and a touch lamp.   Good luck.

73
Ted  W8IXY

The only real CURE is for every ham operator to start filing complaints with the FCC every time & every day there is RFI heard on the station's receivers.

Craig,

Then you would be lucky.  He would most likely be co-operative and willing to correct the problem as quickly and with as little hassle as possible.

Well, that would be nice if the FCC actually acted on the complaints.  I brought up the problem of interference from power lines, part 15 devices, etc., to Bill Cross at the FCC forum at Dayton earlier this year.  Bill deferred to one of the FCC field engineers from Chicago to answer that question.  Oddly enough he was sitting right next to me.  His answer was basically that the FCC doesn't have the facilities or manpower to investigate most complaints directly.  I asked why the FCC hasn't appeared to be vigilant about enforcing interference limits on Part 15 devices before as well as after manufacture.  Same answer, not enough manpower. 

As we watch the circus of Congress proceed through its everyday squabbling, I doubt the FCC will ever be empowered to have any "clout" again, except for the most egregious offenses.

The FCC will spend a lot on resources to shut down some bootleg broadcaster which may interfere with a couple of dozen (or less) licensed stations in a geographical area as small as several hundred square yards, but will allow manufacture of substandard equipment which affects millions of people in thousands of locations. 

73
Ted  W8IXY

As long as amateur radio ops only p&m on the internet and never file complaints with the FCC; then Part 15 is working as intended......there is no interference.

Craig

Although this doesn't sound exactly like your interference, here's what plagued me for months until I found the time to chase it.  Open the attached file to see the waveform and hear the noise.  It turned out to be the built-in battery charger of one of those Scooter motorized wheelchairs at my next door neighbor's house.

The noise was coming in on the power line.  I used a portable AM radio to poke around the house before venturing outside.  I cut the main breaker to the house and there was no change in the noise level or characteristics.  There were hot spots all around the inside the house near electrical outlets and along wire routes inside the walls.  The biggest hot spot was near the breaker panel.  I figured that since the noise was present in the house with the breaker off that the noise was coming in on the neutral, confirming that the power line was acting as an antenna for whatever the source was.

I walked the street and saw that the noise pretty much followed the power line, with a very slight amplitude peak coming from my neighbor's house.  A quick walk through the house with the radio found the culprit.

I hope this is somewhat helpful.  Good luck with your hunt.

73,
Jim
W2BVM

Found-

It is from the Arris WBM760A modem Comcast sent me as an upgrade several months ago. It is located in the shack but I hear it in receivers all over the house. Google product and I get hits all about it. Time to deal with Comcast.

I unplug it and the lower bands drop down to the normal nise I have had here for 17 years.

I appreciate all the help

Carl

Congrats on that one. Cable modem geesh...They'll make it good. I wonder how far it was radiating into the neighborhood?

I have to say Comcast was a pleasure to deal with. The woman I dealt with was a real pleasure, knew her stuff and is sending me a different make/model modem. Said there was no need for me to have that one since I do not have telephone with them.

This was an "upgrade" they provided this summer and I just have not been on that much to really notice it.

Would it be useful for us to catalog these "noisemakers?" We could have a sticky thread or even a forum section just for people to post known RFI generators. The make and model would be listed along with RFI info like freq ranges, type of noise (pulsed, steady, warbling, etc) and of course, recordings and spectrum shots.

Or is there something like this already on the Web?

What say?

Steve
I think that is a great idea
Carl

Good idea, Steve.

There was thread about plasma TVs on either eHam or QRZ some time ago, that listed some that were quiet, and other that were notorious, incorrigible RFI generators. If you decide to start such a thread, let me know and I'll see if I can find it.

Not unusual for a noise like you had to be coming from something nearby, especially with all the junk electronics, light bulbs, chargers, etc. that we all use or have to use.

Fred

I'm looking around to see if any such listing or catalog already exists. The ARRL has a good section on RFI on their website.

http://www.arrl.org/radio-frequency-interference-rfi


One part of the RFI info includes recording which may be of use in tracking down or determining the cause of interference.


http://www.arrl.org/sounds-of-rfi

Steve,

I think it would be very useful. There is information all over the web, but much of it is not terribly useful and to be honest, there's a lot of misinformation and monkey-see-monkey-do myths everywhere. It would be great to have a section where users here could list problematic appliances and hardware they have encountered and effective resolutions for issues they have run into. I will always be grateful for one post in this forum several years ago that mentioned RFI from Philips DVD players. I had put up with that weak but incessant mosquito-like whine on 75 meters for 2 years and had no clue it was my own DVD player causing it!

There is a lot of expertise floating around in this forum that might help others to mitigate the onslaught of noise that is growing daily. We are all at the mercy of what our neighbors pick up off the shelves at Walmart and plug into the grid.

Rob

The voice and data modem here from Comcast is a RCA (by Thomson) Model DHG536C.  With just the lines wrapped around FT-240-77 or -31 toroids its quiet in an old Zenith tube radio 5' away from BCB-18MHz using a 20' hunk of hookup wire on the floor.

Carl

Glad you found the problem.  Every once in a while, I have an RFI "HUNT".  I use a SW radio tuned to 6.5 to 7mhz. 

You will find that most modern consumer gear blasts out RFI.  The latest culpret here was a Neighbors Cell phone charger.  It took out the 40 meter band.

C

It would be interesting to know what caused the noise. My guess rectificers.

Gotta love those switching power supplies.


--Shane
KD6VXI

They may have been a pleasure but they screwed up. The "new" modem arrived today. Exact same model, exact same noise. After all the discussion about sending me a different make and model

The good news is I have been cleaning the shack today and I found the old modem. I thought i had lost it and they had billed me for it. I swapped that out, noise is gone and my speed test produces better results. Interesting the new modem was supposed to be part of a speed increase and at the time did show better speeds. Go figure. Maybe the modem just needed a rest  ;D

So I'm returning both of the Arris WBM760A modems using the older and now faster one and having the rental charge removed.

It all worked out

Hi Carl,

There are so many layers of bureaucracy in cable companies that simple things like a cable modem swap can be bungled easily.

The Arris WBM760A is a Docsis 3.0 modem that supports multiple channel bonding on the downstream and the upstream. My guess would be that the old modem is probably a Docsis 2.0 modem that utilizes a single channel for downstream and another single channel for upstream. You really should stay on them to get the alternate Docsis 3.0 modem sent to you. You will typically have much more downstream bandwidth, less packet loss, and lower pings with the Docsis 3.0 modem assuming the cable company's infrastructure has been upgraded to take advantage of it. Most cable companies are preparing to also deploy multiple upstream channel bonding to allow greater uploading performance within the next 2 - 3 years. I have Cox Cable at my location and have a Motorola SB6120 (Docsis 3.0) sitting 3 feet from the operating position that is RF silent and it doesn't flinch when I run full legal limit on any band.

Rob W1AEX

Rob
I respect your opinion and will do so. But why do the speed tests on line show much faster downloads?

It's possible that the power level and SNR of one or more bonded channels might be off a bit. They refer to this as "tilt" but all it means is that the lower frequencies typically have more gain than the upper frequencies. There could be other factors involved as well. If you can access the diagnostics page of the modem you can see what's going on and bring it to their attention. They should be able to view your modem diagnostics page remotely and send someone out if it needs attention. Once it's set up correctly a Docsis 3.0 connection is far more robust than the older standard.

The picture below shows the frequency, signal to noise, and power level of each bonded downstream channel on my connection. The SNR and power level should not vary by a value greater than 2 between any of the channels. They have been out here all week getting it right and have pretty much nailed it.