FCC Part 15 –5 important points you need to know for Spread Spectrum Applications

Spread-spectrum radio communications, long a15 device manufacturer must design a system
favourite technology of the military, is in the midstthat will not cause interference with, and be able
of explosive commercial development. Drivingto tolerate, the noisy primary users of the
cost down has always been a top goal of anyband.   This is where spread spectrum systems
wireless system designer. The followingexcel because of their low noise transmissions and
paragraphs detail the FCC rules and expand onability to operate in an adverse environment. The
the options available to the system operator orresponsibility for resolving any harmful
integrator.interference to radio services that might occur
Where does Part 15 fit into SCADA?from their use lies with the operator of those
The Code of Federal Regulations (CFR), thedevices.
codification of the general and permanent rulesHow to  choose an external antenna
and regulations published in the Federal Register, isFCC regulations dictate that effective isotropic
divided into 50 titles that represent broad areasradiated power (EIRP) at transmitters cannot
subject to Federal regulation.exceed 36dBm per system when using a 1 Watt
Title 47 of the CFR addressesradio, based on a 6 dBi antenna.  1 watt transmit
Telecommunications and is administered by thepower (+30 dBm) plus 6 dBi antenna gives the
Federal Communications Commission (FCC). One+36 dBm EIRP limit. More transmit power and less
of the most commonly referenced parts of Titleantenna gain, or the opposite, is ok as long as you
47 is Part 15, which covers the regulations underdon't exceed that number.
which an intentional, unintentional, or incidentalThey don't talk about losses in cables, filters or
radiator that can be operated without an individualconnectors but those must be included. As an
license. This covers as well the technicalexample, if you had 3 dB of losses and a +30
specifications, administrative requirements anddBm transmitter, then you could use a 9 dBi
other conditions relating to the marketing of FCCantenna. If you want a higher gain antenna for
15 devices.more directivity, say 12 dBi, then you need to
FCC Part 15 Subpart C governs intentionalreduce the transmit power to +27 dBm.
radiators. The various types of intentionalFor anyone selling spread spectrum wireless
radiators covered by Subpart C include cordlesssystems, these limitations are a key factor in
telephones, remote control and alarmoverall system design.  Key resources include the
transmitters, and spread-spectrum systems forradio manufacturer itself; the top manufacturers
wideband data transmission. Intentional radiatorsare quite prepared to make recommendations for
governed by Part 15 FCC must either incorporateany given application. Path profiles or actual site
a permanently attached antenna or provide asurveys provide the best methods for
unique coupler to prevent the use ofdetermining appropriate antenna gain values.
un-authorized antennas.For typical oil & gas SCADA applications, the
The FCC rules for operation of radio transmittersmost common choices for remote sites remain
are, for the most part, very detailed regardingunity gain omni-directional, or 8 dBi and 12 dBi yagi
fundamental field strength, power and/or power(directional) antennas. Typical master
density, frequency accuracy, and permittedomni-directional base station antennas are usually
harmonic and spurious emissions.5 dBi or 8 dBi models.
Part 15 FCC regulations emphasize that the Part