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Sherlock Investigates 630 Meter Noise

Created by Paul Signorelli, W0RW on 2019-09-04

Sherlock Investigates 630 Meter Noise

Tracking 630 meter noise is really hard. I have a little AM transistor radio that helps me to track down offending radiators. I also use my BC-453 that has an "S" meter.

So to start off in a good `shot gunning' manner, I bought a dozen Schaffner FN2080-3-06 (3A) Power Line Filters (From eBay) for my low current items and put them on all the worst radiators around the house.

I have a 6A filter, Rockwell Automation 2090 for bigger power supplies that needed it.

Then I built a RFI filter for my Battery Chargers using 2 big Sprague 10JX34, 10A, feed coaxial feed filters.

I don't mind noisy things that I can switch off or unplug, I have them tagged.

(My XYL's new Speed Queen Washing machine has gobs of digital noise coming out of it, even when it is off! I contacted the factory and told them the "Off" switch doesn't turn the machine OFF! They said I need to buy a 15A line filter, that has no specs.

However there seems to still be noise out there coming through my antenna.

I installed a battery back up switch-over system for my K3s LF Rig and waited.

Yesterday, something blew a Utilities line breaker and the whole neighborhood lost power. Happy day for me, My K3s was finally operating in an area where there was no local power. The noise was still about the same and but now I have a noise base line and know most of my house noise has been eliminated.

One of the worst offenders was a Wall Wart converter that had more noise on 630 meters when the electronics it was powering was off than when it was on. That one went in the trash.

Use caution when hooking up line filters. There must be a hot line side (black wire) fuse that matches the current capability of the filter and you are going to have 110V AC terminals exposed that will need insulating. If you have a Earth Ground (green wire) line connection for the filter case try it first and then try using no neutral connection to see which is best at noise reduction.

Read the ARRL Handbook EMI section, Chapters 9 & 28 for exact methods of connection.

Sherlock, W0RW

KX4Z 2019-09-18
RE: EMI home sources
Thanks guys, for all these great tips!!! Very much appreciated. I'm going to build a loop....
AF6AU 2019-09-16
RE: EMI home sources
Any clothes washer or dryer (except an outdoor clothes drying line) in these modern times use switched mode 3 phase motors instead of gears, pulleys, and belts to change speeds. Placing a nice grounded EMI/RFI filter INSIDE the machinery where the line power enters is paramount. My washer makes horrible "Zip-Zip" noise on 20 meters. The dryer is not bad since it runs constant speed. The new dishwasher is also variable speed with the pump, so it's a new addition. Digital clocks in applicances along with processors in everything from refrigerators to toasters, also contribute.

My worse offender??? High speed DSL internet coming into the neighborhood on twisted pair telephone service lines. Every house with it mixed with poor distribution coax is a radiator. TV BUZZ all over the bands. And since the FCC makes big $$$ from the telephone people, if you report the interference, the FCC guys more or less ignore you (Long Beach Calif. office anyway).

Second worst offender? The Neighbor's Plasma TV. Thanks Lord for blowing the power supply capacitor.
DL4NO 2019-09-08
Start at Home
Most of the RFI is wire-bound. This is why it is so difficult to pinpoint it: It blows out everywere. Most sources are too small to contain effective antennas.

The first thing you should do is: Switch off one of your circuit breakers at a time. If the noise drops, you know a corner where to search. Then pull one wall plug after the other.

Common-mode yokes on 630 m are difficult to make. Pre-fabricated line filters are a good start, but cannot be used in every case. Get high-permeability ferrite cores and put as many windings on them as possible. Also remember that RFI can be differential-mode. Then you need a yoke on every single wire, not only for the cable as a whole.
KI4ZUQ 2019-09-08
Sherlock Investigates 630 Meter Noise
Don't forget those "touch" lamps! Huge noise!
W9IQ 2019-09-07
RE: Sherlock Investigates 630 Meter Noise
Using common type 31 or 43 ferrite material for EMI suppression on the 630 meter band is generally not optimum. You will likely find more success experimenting with type 77 material.
NA6O 2019-09-05
RE: Sherlock Investigates 630 Meter Noise
First, consider adding proper common-mode chokes to known RFI generators. Commercial line filters are generally ineffective on CM noise because the ground connection is common to both sides of the filter, allowing that current to pass. See

If you’re looking for quiet 5V supplies, first try to find old linear ones on ebay (they are getting rare). Or get a genuine Apple adapter which has a remarkably low noise level, both normal-mode and common-mode. See my review at

The lowest frequencies are always going to be challenging for RFI suppression and I’m interested in seeing what else you discover.
VE3LNY 2019-09-04
Sherlock Investigates 630 Meter Noise
I took around 6 5V 1A wall-warts, the kind used to charge gadgets, put a load on each one and scoped the output. Four of them were nice and quiet, two were loaded with noise and went in the trash. It's easy to screen these things and get rid of the bad ones. 73
W0RW 2019-09-04
RE: Sherlock Investigates 630 Meter Noise
Thanks for the question.
I did leave all those things out.
Most of my noise came from switching wall warts and battery chargers. Computers, routers, network wiring, display and TV screens were bad. Surveillance cameras were very noisy. Once you get a base noise level without any AC power on, you can usually find the rest. Correcting them is more difficult. One neighbor had an old folks scooter that had a powerful charger which sent me noise from 500 feet away. Neighbors fish tank heaters can be noisy. One neighbor just had a loose "F" coax connector on his TV, after I tightened it up the noise went away.
Clamp on ferrite chokes work on high frequencies but usually not too good at 630 meters, I add them anyway too keep HF clean.
You have to be able to DF (Direction Find) the sources.
An old transistor radio tuned to 540 kHz will do a good job.
AA4MB 2019-09-04
Sherlock Investigates 630 Meter Noise
Dear Mr. Holmes,

First, thanks for the article. There's a metric crapton of local noise on HF period ... but on 630 meters, at this location, it's much worse. However, what isn't present in what you wrote may be at least as important as what is there:

> I bought a dozen Schaffner FN2080-3-06 (3A) Power Line Filters (From eBay) for my low current items and put them on all the worst radiators around the house.

> I have a 6A filter, Rockwell Automation 2090 for bigger power supplies that needed it.

> Then I built a RFI filter for my Battery Chargers using 2 big Sprague 10JX34, 10A, feed coaxial feed filters.

You go on to talk about what some of the worst offenders are/were, and that's great. I do wish that you had gone into more detail and given a more comprehensive list of what the 'worst radiators' were. Also, are the 'battery chargers' you described all wall warts? Do you have a car battery trickle charger also?

Please understand, this isn't criticism of the article, but using a few more examples makes this far more useful for everyone. For what it's worth, the new washing machine that my wife purchased when I was out of town on business (don't get me started) is an excellent RFI source. Unlike yours, thankfully it only radiates when it's actually operating. :)


- Matt, AA4MB