Steps to Lower Noise Floor and Revitalize AM Radio

Noise interference is the menace of all wireless broadcast communications services

The author is president of Kintronic Labs Inc.

Background noise interference is degrading the quality of broadcast reception, two-way communications, mobile cellphone services and every other form of wireless communications used today at an alarming rate.

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Noise Inquiry Spurs Recommendations

Test setup.

The FCC and the ITU agree that the DC to 60 GHz+ wide-spectrum background noise floor is increasing as more and more unregulated electronic devices are used by more consumers in more ways every day.

While it is true that large numbers of these devices have been in use for some time, the question becomes: What can we do to lower the noise floor now that the floodgates of unregulated devices have been open for so long? Is this an impossible task? I believe the answer is an emphatic “no.”

On June 15, 2016, the FCC Office of Engineering and Technology Technical Advisory Council opened a noise floor technical inquiry in the form of ET Docket No. 16-191 to seek answers to the following basic questions:

1. Is there a noise problem?
2. Where does the problem exist? Spectrally? Spatially? Temporally?
3. Is there quantitative evidence of the overall increase in the total integrated noise floor across various segments of the radio frequency spectrum?
4. How should a noise study be performed?

The most prominent responses were from the American Radio Relay League, the Society of Broadcast Engineers, the NAB, the National Public Safety Telecommunications Council, the National Electrical Manufacturers Association, the State of California Governor’s Office of Emergency Services Public Safety Communications, Verizon and AT&T.

Unfortunately, most were anecdotal, not accompanied with measured quantitative data. This is largely because the responders did not have the instrumentation resources nor the budget to provide the quantitative evidence being sought.

Despite the scarcity of quantitative data submissions, one clear outcome of this TAC technical inquiry is an unmistakable consensus among the responders: A noise floor study is not only needed but overdue.

AC power cord +/- 3 V P-P impulse noise.

TESTING

In August 2016, Jack Sellmeyer, P.E., and I measured the electric field intensity and the associated (power cord) impulse noise voltages produced by various LED lights that we purchased off the shelf at a Home Depot that resulted from the lack of filter components in the lamps. One of the lights we tested was a Phillips 100 W LED light bulb.

The test setup in the image above shows the flat line trace on the oscilloscope with the LED light off, and the oscilloscope trace on the right shows the +/- 3 V peak-to-peak impulse noise that was measured using a current probe on one of the two AC power cord conductors when the light was turned on.

The associated field intensity measured at 3 MHz was 35 uV/m with the loop antenna immediately adjacent to the lamp. This value quickly decreased to the noise level in less than 1-foot distance from the lamp. Hence, the most significant noise contributor from this particular lamp was the conducted impulse noise that was due to the fact that the currents on the two AC power leads were not equal and opposite. The proper filter components had not been included in the lamp design.

Another lamp that we tested was a Philips 100 watt flood lamp. This light yielded a field intensity at 3 MHz of 400 uV/m at a distance of 3 inches from the light, which decreased to the noise level 5 feet from the lamp. We located the FIM-41 loop antenna adjacent to the lamp power cord feeding this lamp and walked it down the length of the power cord for a distance of approximately 10 feet from the lamp.

The field intensity ranged between 60 and 70 uV/m over the length of the power cord measured. It never dropped below 60 uV/m. The audible noise associated with the RF emissions from these lights at 3 MHz was undeniable. These results together with other video recorded test results were submitted in response to the TAC inquiry.

These are just a small sample of the numerous LED lights that are available. You can imagine the cumulative results for multiple LED lights in one residence or manufacturing plant.

These lights are just two examples of a plethora of RF-emitting consumer products, including compact fluorescent lights; LED traffic lights; all manner of switching power supplies associated with commonly used consumer electronic devices, such as computer modems, LCD and plasma TVs, cell phones, computers and UPS units; automobile electrical systems and controllers; and photovoltaic power systems that are now commonly used throughout the United States, Canada, Mexico and the developed world.

WHAT TO DO

We at Kintronic Labs believe that the following steps should be taken to lower the noise floor and specifically to revitalize AM radio:


1. FCC Lab should perform random off-the-shelf product testing of consumer electronic products to confirm compliance. Manufacturers found to be guilty of selling non-compliant products should be issued commensurate fines that will serve to inform them and other manufacturers that the manufacture and importation of non-compliant products into the US market will not be tolerated.

2. AM stations must become actively involved in reporting utility and Part 15 and Part 18 home device offenses to the FCC. Provisions for doing so are now available on the FCC website (https://www.fcc.gov/consumers).

3. The NAB, SBE, ARRL and other wireless communications associations need to take an active role in keeping up with new technology developments and identifying the potential impact they may have on the RF noise floor. One example is the wireless charging systems being developed for electric cars. Some of the planned systems will operate at power levels of tens or hundreds of kilowatts at frequencies of a few hundred kilohertz. One can expect that even a relatively small amount of harmonic emission from such devices could wipe out radio reception over long distances.

The author thanks Bob Weller, P.E., president of the Association of Federal Communications Consulting Engineers, for helpful comments incorporated in this article.



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