Radio World has
focused a great deal lately on the needs of the U.S. AM band, as we
cover the industry debate over how — and whether — the FCC should
help “revitalize” AM. You’ll find plenty of interesting
material at radioworld.com/amcomments.
insights are the following, filed with the commission by the Society
of Broadcast Engineers. I reproduce them because I find this section
of SBE’s comments — almost a sidebar to its main points — a
helpful addition to the many suggestions floating around regarding
translators, MDCL, efficiency standards and so forth. (I’ve added
some paragraph breaks for ease of reading.)
AM revitalization, in
SBE’s view, is not entirely a deregulatory exercise. Some existing
regulations should be better enforced, and some new regulations will
be required in order to improve ambient noise conditions in the
existing AM band. It is obvious that any interference management plan
for the AM band has to be based on rules [that] limit RF noise before
it becomes an issue, not post hoc, and those rules have to be
As but a few examples:
limits below 30 MHz in FCC Part 15 rules for unintentional emitters
such as plasma television receivers should be enacted.
[At present there] are
no radiated emission limits below 30 MHz for most unintentional
emitters. Only conducted limits exist now. This has become a
short-range problem with respect to interference from some emitters,
such as cellular telephones (especially in charge mode) and plasma
television receivers. Direct radiation from … plasma display[s] can
be problematic for AM receivers and difficult to remedy.
The commission should
consider establishing limits on the amount of noise that can be
radiated directly from such devices.
Lower limits in Part 15
for LED light bulbs should be enacted [that] are harmonized with the
lower limits for fluorescent bulbs in the current Part 18 rules.
Part 18 rules govern
fluorescent bulbs. Those Part 18 limits are lower than the Part 15
limits [that] govern LED bulbs. The Part 15 LED bulbs typically
operate at levels 12 dB higher than Part 18 fluorescent bulbs. All of
the reasons that caused the commission to establish reasonably low
limits for fluorescent bulbs exist for LED bulbs.
There are apparently
very few, if any, interference reports involving fluorescent bulbs
that meet Part 18 consumer limits. There are, however, substantial
numbers of complaints of harmful interference to amateur radio
stations from LED light bulbs on an annual basis. This is a good
example of an RF management problem that must be addressed before the
devices are marketed.
There could be dozens,
if not hundreds, of RF light bulbs in range of a typical AM broadcast
receiver in a typical residential neighborhood. If harmful
interference occurs and is reported, there is no practical, post hoc
solution. Filtering of the bulb is not an option. They couldn’t all
be found, even if adequate commission resources were available to
investigate such instances. Even if they were to be found, the user
of an RF light bulb that contributed to AM receiver interference
would not likely be ordered by the commission to stop using it.
labeling on packaging for Part 18 fluorescent bulbs and ballasts
should be ordered.
Part 18 rules have
separate limits for consumer and commercial fluorescent devices. A
number of box stores and large hardware and consumer retailers,
including some well-known nationwide chains, are openly selling
commercial fluorescent bulbs and ballasts to residential consumer
users. [At present] there is no information on the outside of the
packaging for these devices indicating that they are not legal to use
in residential environments. These same big box stores are all
selling Class A industrial lighting ballasts.
There is material in
the Office of Engineering and Technology’s “Knowledge Database”
(KDB) clarifying that such marketing is not legal and that the
labeling, or even signage and warning, is not enough. If this policy
(it is not a specific rule) were to be enforced, the big box store
would claim that they can sell commercial environment ballasts
because they also sell them to buyers for that market, but the
devices are on display and the general public is not informed of the
proper environment in which to deploy them.
and/or conducted emission limits for incidental emitters such motors
or power lines should be enacted.
commission rules, there are no specific emission limits for
incidental emitters such as power lines and non-pulsed motors. There
are requirements for manufacturers of incidental emitters to use good
engineering practice and a requirement that the operator of an
incidental emitter use them in a way that does not cause harmful
interference to licensed users of spectrum. Those rules are neither
enforced, however, nor practically enforceable.
limits would set an upper level on the worst of the power-line noise
cases and would require manufacturers to pay at least minimal
attention to design and utilities to evaluate their entire systems at
least sporadically, assuming that they perceive that there is a risk
of actual commission enforcement. Although conducted-emission limits
could be established for motors and similar 120- or 240-volt devices,
only radiated limits would be practical for medium-voltage or
high-voltage power lines.
limits on pulse-width motor controllers used in appliances should be
Under Part 15 rules,
“digital devices” used in appliances are exempt from specific
emission limits. There are instances of interference to AM receivers
from pulse-width motor controllers in washing machines, air
conditioners and pool pumps. If pulse-width motor controllers are
digital devices, then these 500- to 1,500-watt digital devices would
be exempt. Most digital devices that are used in appliances are very
low power display units, microprocessor control circuitry and similar
devices [that] have a much lower interference potential than
1,500-watt motor controllers.
The commission should
substantially increase, and increase the visibility of, enforcement
in power line interference cases.
There are numerous
complaints from amateur radio operators of severe interference from
power line noise annually. Power line radiation in the HF and MF
amateur allocations will in most cases directly translate to
preclusive noise in the AM broadcast band.
The commission has
relied completely on the good-faith efforts of electric utilities to
resolve these. In some cases, those efforts have been successful.
However, more often, utilities do not have available to them and are
not willing to retain persons skilled in RF interference resolution
and the cases at FCC are allowed to languish unresolved for years,
and in some cases more than a decade, without any enforcement action
at all. …
AM radio interference
inevitably goes unreported by listeners. A few visible enforcement
actions by the commission would create some incentive on the part of
electric utilities industry and perhaps lead to the development of
effective industry programs to address the burgeoning power line
Improvement in the
noise environment in the AM broadcast band will, over time,
contribute substantially to the revitalization of AM broadcasting.
The commission should commence this longer-term initiative without
This was just a
portion of SBE’s comments, which included several specific
important recommendations. Read the rest at radioworld.com/amc