[South Florida DX Association] BPL

william greeson [email protected]
Wed, 7 Jan 2004 08:47:14 -0500


California firm develops interference-free BPL technology

 Canadian radio amateurs using the high frequency and VHF spectrum are =
becoming concerned that proposed broadband over power line (BPL) systems =
may render the bands unusable due to radiation from the power lines.  =
Broadcasters and government agencies also fear that BPL radiation, =
including harmonics, have the potential to cause interference to VHF TV, =
FM radio and military and public safety communications in the HF and =
lower VHF spectrum.  =20

Six weeks or so ago, I read a story that a California company, Corridor =
Systems, had demonstrated a BPL system that works at 2.4 and 5.3 GHz. =
The system, is designed to provide broadband  (250 MHz) transmission =
suitable for high speed Internet access, using the existing power =
distribution system, but which does not pose any threat whatever to =
amateur radio or other users of the rf spectrum.=20

 I tracked down Corridor Systems Chief Technology Officer, a radio =
amateur, Glenn Elmore N6GN, and he assured me that their BPL technology =
would not interfere with the HF ham bands. The story below is based on =
information found on the Corridor Systems web site.=20

 Corridor Systems has developed and patented core technology that =
enables very high capacity, symmetric and full-duplex information =
transport over a variety of propagation medium types. Power Corridortm =
is an implementation of this fundamental technology which operates, in =
part, over a single conductor of an unmodified, existing power line. In =
Power Corridortm, information-carrying energy is coupled on and off the =
conductor by identical launch devices at each end of conductor segments. =
This energy, which may extend from VHF through the microwave portions of =
the spectrum, is launched as a surfacewave mode around the conductor.

Surfacewave transmission on an insulated single conductor was first =
discovered and presented by Goubau1 in the early 1950's and known as =
G-Line2 after the inventor. The characteristics of surfacewave  =
propagation, when used with a variety of dielectric types, thickness and =
specially prepared conductors, have been taught and available in =
reference texts for many years3. Though not widely utilized in practice, =
the mode can exhibit extremely low radiation and transmission losses =
from VHF into the microwave regions.

Corridor Systems has discovered, extended, developed and patented a much =
more general surfacewave mode for operation on lines which may be =
completely uninsulated and which need not have any special surface =
preparation. Additionally, lines which are much larger in diameter than =
those of previous work may be utilized. This invention, which makes =
possible very high rate information transport over existing =
medium-voltage electric utility power lines, is called E-linetm. As with =
G-line, the vast majority of energy propagates within a volume located =
relatively close to the single conductor. In Power Corridortm the =
diameter of this volume is only a few inches. Since the energy =
propagates at very nearly the speed of light, the relative velocity of =
propagation in this mode is quite close to unity.

Combined with the normal clearances maintained for aerial medium and =
high-voltage power lines and Corridor System's specially developed and =
patented launching devices, E-linetm provides an extremely effective =
mechanism for the transport of very high speed information over existing =
power line grids.=20

 Measurements at ground level directly under the power line used during =
the test showed a maximum radiated power level of less than -10 dBm, 20 =
dB less than the typical power level from 802.11 based wireless cards.=20

Corridor Systems has tested and demonstrated simultaneous operation of =
its BPL technology and amateur radio HF communications. Utilizing a 100 =
watt, 7 MHz, 21 MHz and 28 MHz amateur SSB/CW transmitter connected to a =
dipole antenna located within 20 feet of an operating BPL system, there =
was not any evidence whatsoever of the operation of one system in the =
other. Amateur UHF communications at 446 MHz and at a 25-watt power =
level were similarly unaffected and in turn were not detected by the BPL =
system. Examination of the .1-30 MHz HF spectrum with a quality =
communications receiver also revealed no evidence of the BPL system.=20

 Glenn also told me that Corridor's demonstration not only used the =
unlicensed bands, FCC Part 15 in the US, but also simultaneously =
supported fast scan amateur television with stereo audio under Part 97 =
of the US Rules. So while the system was being used to support high =
speed internet traffic it also served as an "open band" for amateur =
radio uses-- even with one end of the TV link mobile on the roadway near =
the power lines!=20

 More information and photos can be found at:=20

http://www.corridor.biz/news.htm and=20

http://www.tvtechnology.com/dlrf/one.php?id=3D259 =20


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