Monday, April 3, 2017

Can incandescent light bulbs cause interference?

In an article I wrote several years ago, I implied that in our quest for energy efficient lighting solutions, the move from incandescent to alternatives such as LED lighting have introduced some new problems with radio interference that we didn't have with incandescent light bulbs.  Well, actually that wasn't exactly true. We did have interference and the "problems" are not new but, a different manifestation of an old problem.

Recently the European market surveillance authorities (AdCos) on EMC have been investigating the potential of incandescent light bulbs to cause radio interference. The investigation began with reports that some incandescent lights may be the cause of reported interference to FM broadcast reception. The findings show that a specific type of incandescent bulb can interfere with radio reception.  The type is referred to as a 'squirrel cage' Edison bulb in the report.

As an Electromagnetic Compatibility engineer, this came as a bit of a surprise to me. It's been accepted by EMC experts that an incandescent light bulb on its own wouldn't emit radio signals, in fact, the European standard covering interference from lighting states; 
"incandescent lights "are not expected to produce electromagnetic disturbances"  
yet this new data proves otherwise. So what's changed?  After a bit of research I found the answer, nothing, we've just stumbled on an old problem inherent to the once obsolete but now trendy retro vintage style vacuum Edison bulb.

In the United States, the problem was known in the 50s to cause interference with T.V. reception. Although not in production in the U.S. at the time, there were still a number of the straight tungsten-filament Mazda bulbs in use. Tungsten-filament bulbs of the Mazda type were initially more costly than carbon filament bulbs but used less electricity. A direct comparison to the LED vs Incandescent light bulb today

This Popular Science article from 1953 titled "U.S. declares war on static", a campaign of hams and hobbyist sponsored by the FCC shows an example of how to identify T.V. interference from an obsolete light bulb. Today's filament light bulbs use an inert gas and relatively small coiled filament rather than a hard vacuum and a long zigzag filament structure.

An investigation of the science and physics behind the phenomenon indicate this is caused by the filament oscillations coupled with thermionic emissions from the heated filament in a hard vacuum, similar to properties found in vacuum tubes. This post "Rustika lightbulb FM measurements " provides data and analysis and links to other works. 

So in conclusion, if you're having new and strange problems with radio reception, and you've installed one of those vintage light bulbs, try unscrewing it.

Did you find this helpful, or informative? Please leave a comment or like below!

EUANB (17)003 Report from EMC WP 25 (February 2017)
When Technologies Collide! Radio Interference from Light Bulbs (May 2010)

Me: I work for Compatible Electronics, Inc. an accredited U.S. test lab and product certification body.

Monday, March 27, 2017

FCC expands AB accreditation of labs in non-MRA countries

On March 23, 2017, the Federal Communication Commission daily digest published the expansion of scope to include accreditation of labs in non-MRA countries for two United States based laboratory accreditation bodies (AB), the National Voluntary Accreditation Program (NVLAP) administered by NIST and the American Association for Laboratory Accreditation (A2LA).

The term MRA stands for Mutual Recognition Agreement. This reciprocal agreement between nations in its simplest form is an agreement to accept one another’s local conformity assessment body’s assessment of local laboratories and inspection bodies for testing and certification to the other country’s requirements. 

In an over-simplified sense, “You accept my test results, we’ll accept yours”. You can find a more thorough explanation and a list of countries with which the United States has an MRA in place on this FCC page.

For non-MRA countries there is no established government to government agreement to accept the other’s compliance assessment, many of these non-MRA countries require an inspection to be carried out by their own domestic labs or by an appointed government department making it far more expensive and time consuming to import into such economies. 

Some non-MRA countries follow other MRA programs such as the ILAC MRA that help to lower the time and costs associated with testing/inspection and facilitate trade.

The largest example, by population, of countries that do not have an MRA with the US, is commonly referred to as “BRICS” which stands for Brazil, Russia, India, China, and South Africa. 

With the expansion of scope for the two US accreditation bodies to include non-MRA countries the FCC opens a path for laboratories in non-MRA countries to test products for import to the US and provides a mechanism for quality control. 

Some have suggested that this may disincentivize non-MRA countries from pursuing a future MRA, which ultimately may have a negative impact on domestic test laboratories and small to medium scale domestic manufacturers.

What are some other considerations, good or bad, on the acceptance of non-MRA country assessments to US requirements?

Me: I work for Compatible Electronics, Inc. an accredited U.S. test lab and product certification body