Joined: Sun, Oct 30th 2011, 02:35 Roles: N/A Moderates: N/A

Latest Topics

Topic Created Posts Views Last Activity
Wall_Wart RFI and Where did all those linear wall-warts go? Nov 18th 2016, 21:50 2 107 on 19/11/16
RFI and Residential Marijuana Grow Operations Jul 4th 2016, 15:26 2 322 on 4/8/16
ARRL News Hotline Jun 17th 2014, 00:09 1 861 on 17/6/14
E&M Modeling Software? Jan 1st 2012, 05:36 2 1,617 on 1/1/12
Xcvr Repairs? Jan 1st 2012, 05:05 4 2,212 on 6/2/12
Broad Band Interference Jan 1st 2012, 03:51 14 3,013 on 14/2/12
Kenwood TR-751A Memory? Dec 17th 2011, 05:37 3 2,323 on 20/12/11
Wideband RFI Bursts - Please Help! Nov 20th 2011, 21:49 11 2,959 on 11/5/12

Latest Posts

Topic Author Posted On
Wall_Wart RFI and Where did all those linear wall-warts go? AC0XU on 18/11/16
In my perpetual battle to combat RFI, I have replaced nearly all of my household copper gigabit ethernet with fiber. However, I now find that the wall-warts that power the fiber switches and media converters generate RFI by conduction through the DC and AC lines and by radiation through the plastic cases. The Ethernet-related RFI is more localized but not much better!

I have been completely unable to find LINEAR, REGULATED wall-warts to replace the switched ones that are SO noisy. There are still some linear (transformer) wall-warts on the market, but they are not regulated, consisting of just a transformer, bridge rectifier, and capacitor. For example, a nominal 9 volt linear wall-wart may put out 12 or 13V at no load, which is too much for some electronic devices, They overheat.

While I am willing to pay more for an old-fashioned, linear regulated power supply, what is available is large in capacity, size and price (e.g., 20A+, 20Lbs, $150). There are also audiophile power supplies which are overkill and expensive. I know that some hams try to run everything off a main 12V power supply (with some other solution obtained for 9V devices), but running DC power lines all over the house is a lot of trouble and they would pick up noise that would have to be filtered out to boot.

I believe that part of the drive to switching power supplies has been to increase efficiency. Some websites praise these monsters as great innovations (obviously, not hams)! Also, it seems that the Chinese can manufacture a 60KHz tesla coil aka wall-wart much more cheaply than make 60Hz transformers. However, surely there are ways that a non-RFI-emitting power supply can handle varying loads while still providing high efficiency....

Before I break down and start building compact linear regulated supplies from scratch, does anyone know of a source for reasonably priced 9 and 12 V linear, regulated power supplies in the 0.5 to 5 amp range?


LED light bulbs cause RFI W7DRM on 4/7/16
I have found that CFL bulbs are almost universally worse than the LED bulbs, so I have replaced all the CFLs around my house with LEDs. Sounds like bad luck there with your purchasing choice. I have had good luck with Cree LED bulbs, which Home Depot sells in my neighborhood. You also might want to try Philips bulbs - I don't have RFI data on their products but in my experience Philips makes what are probably the world's highest quality light bulbs in general, so we might conclude that they engineer their products better than other manufacturers.
RFI and Residential Marijuana Grow Operations AC0XU on 4/7/16
Various other neighborhood RFI problems have come and gone. My neighbors have not been cooperative. Cable boxes have been one culprit. Others, I don't know, but after a year or more most RFI sources just go silent. It has been worrisome that Solar City installations have been going in but so far they seem to be reasonably quiet, at least compared to the following problem.

The latest RFI source which wipes out all HF operation during the day is the marijuana grow operation 2 houses away. I first found out about this when the power kept going off. The electricity linesman told me that house consumes about 10x the normal residential draw. Add to that the blacked out windows, dogs and security systems... A portal radio with a loop and a 360 degree walk around the house makes it clear where the RFI is coming from. Excel Energy installed a larger transformer, which solves the outage problem, but does not eliminate the RFI!

This is a clear zoning violation but the city won't do anything. The police have been monitoring the situation but they say they can't shut down the grow operation until they have sufficient evidence. Considering the nature of the business, I am reluctant to confront the residents.

The grow lights raise the general noise level over all the HF bands around 10 dB. With directional antennas, including several loops and a hex-beam, I can occasionally copy a few signals that come from orthogonal directions. Anything within 45 degrees of the direction to the neighbor's house is nearly impossible.


Mystery signals 53.335kHz harmonics K3KXJ on 17/6/14
This is typical of noisy switching power supplies. The signal gets into house wiring, plumbing, coax, etc and can be difficult to DF. Power off everything at the main breaker in your house. Run your radio by battery - if you are still seeing the RFI then it is not coming from your house equipment. If the RFI goes away, turn on the breakers one by one until you track down the culprit.

I have seen this kind of RFI from cable modems, satellite TV equipment, and other folks have reported it from lighting systems, electric blankets, fence chargers, and wall warts.
T8 Lamps W1MG on 17/6/14
I have done testing on T12 T8 and T5 shop lamp fixtures purchased from Home Depot. I have found that T12 are consistently noisier than T8 which are consistently noisier than T5. People say that the electronic ballasts are noisier than the transformer ballasts, but I have not found this to be the case. Fluorescent tubes are nonlinear devices and they produce high frequency EM even when driven at 60Hz (really 120 Hz). Possibly, a transformer ballast system could be combined with appropriate capacitors to reduce ringing, but such systems don't seem to be made. I recommend going with the T5's. Use the high intensity bulbs for a few more dollars if you need a lot of light - they are really bright.

With all of the above, I have the following recommendations:

1) Use only fixtures with metal shells (some are plastic - avoid these).

2) Be certain to ground the light fixture case. If you fail to do this, all of the fixtures will emit considerable RFI.

3) Little RFI appears to come from the fluorescent tubes themselves. It mainly comes from the wiring. Ground the case containing the wiring and the ballast, and you eliminate most of the emissions.

Back to Top