Subject: [NEXTEL-1] RE: BPL

From: [email-masked]
Date: Sat, 13 Sep 2003 11:57:31 -0400

------- Original Message --------
   From: "Todd Ellis" <[email-masked]>
Subject: RE: BPL

Guys - I agree with you!  But!!!!!  Please keep your minds open.  I'm the
narrow-minded one on this subject?  Read on, from Ed Hare (of the ARRL):

Measurements were made of the field strength present at several of the test
locations. At test site #1, the user had linked his home computer to a streaming
video site to provide a constant signal during testing at that location. On 12
MHz, the BPL-noise field strength at this location was measured as high as 23.0
dBuV/m with the short-dipole antenna located approximately 5 meters below the
overhead power lines, with the mobile installation parked on the street. Another
measurement was made on 5.3 MHz, using a 7-MHz half-wave dipole, matched to 5.3
MHz using an antenna-matching network. This antenna was located a height of
approximately 6 meters, 3 meters in front of the house, approximately 12 meters
from the street. This would be a reasonable amateur installation for that
neighborhood of close-spaced houses. The level on 5.3 MHz at that antenna was 6.6
dBuV/m[4]. The measured ambient noise level when BPL signals could not be detected
averaged around -6 dBuV/m on 5.3 MHz to -3 dBuV/m on 14 MHz.

At test site #3, measurements made from the street, across the street from the
lines, ranged from +28 dBuV/m at one location measured from the vehicle parked
across the street from overhead power lines to +35 dBuV/m at another where the
antenna was raised to a height of about 5 meters above ground. In test site #4,
ARRL measured +32 dBuV/m at one location about 10 meters diagonally from the power
lines, with the test antenna located at a height of about 3 meters[5].

Now - here's some questions I have - why weren't the tests run at 3.999 MHz or
7.001, in the ham band?  Why was 5.3 MHz used?  One test was done 15 feet from the
power line, and another was 40 feet.  What happens at 100 feet? 150 feet? 200
feet?  The argument that 40 feet is a good judge of distance is interesting, since
the antenna at 7 MHz (assuming a dipole, as used in the test) will be about 66
feet long all by itself.  This gets back to OET-65 and radiation issues, too.  My
75 meter antenna at 124 feet long was 150 feet from a power line parallel, and 80
feet perpendicular (I was on a corner lot), and the power entrance was on the
other side of the ranch house, 80 feet from the near tip.  What I'm getting at is
that these tests were done in worst-case situations, and were done in such a way
as to especially expose the problem, not to clarify the issue.

To compare, when my NorthStar engine was eating 6 quarts of oil in 1,000 miles, I
was asked to drive it in 500-mile increments and let the Cadillac folks monitor
the level.  Sure, they ripped the engine down at long last and replaced the rings
(and a few other things that were busted), but I endured the 2,500 miles to verify
the problem.  I see the ARRL test as being close to the first stop at the
dealership.  We need more data.

I am especially interested in the Manassas test they ran, see below.

Test Area #2 -- City of Manassas, VA

ARRL made only one visit to this trial area, so only limited testing was
performed. In this area of underground wiring, the interference level was
moderately strong. A single example of this is shown in the video documentation.

This system is underground, and pops up into shielded utility boxes where they
inject the signal using inductive coupling.  How is it leaking to the surface?  Is
the interference coming from the power entrances or leaking from underground?  How
high above the ground and how far away horizontally do you have to be before the
signal attenuates significantly?  Since most HF antennas are mounted 20-60 feet
above the ground for optimum performance, these questions are valid.  No answers
yet!

On to Mark's point, which the ARRL understands, but states:

[3] To ARRL's knowledge, neither ARRL nor any of the BPL manufacturers have made
testing at heights above the power lines to determine the true points of maximum
emissions from the lines. These would have significant applicability to the impact
of the radiated emissions on aeronautical communications, areas located above the
lines on hilly terrain or to antennas located on towers that are taller than the
lines.

I think MORE TESTS are needed.  Perhaps airborne communications are potentially
the most significant to be affected.  In that case, folks like ARINC and the Air
Force need to test immediately, and then report their findings to the Commission
and the public.  Has anyone run such tests?

Guys and gals, as I started to say, I agree with you - this technology has some
potentially bad interference issues to contend with.  Yet where are the tests to
show these statements are valid?  As a ham who only operates HF mobile and who
would be directly affected, I'd like to see them!

I suggest that someone hire an independent consulting professional engineer with
telecom and power engineering backgrounds to investigate the issue conclusively.
Contact me off line if you need to find such a firm, I have several suggestions of
good firms who can do the work from various places across the country.

In all of my professional experience, the question has to be why - why - why.  All
I hear is fire - fire - fire, and no one is getting past the first whiff of
smoke.

Todd Ellis

-----Original Message-----
From: A10382 [mailto:[email-masked]]
Sent: Friday, September 12, 2003 9:11 PM
Subject: Re:  BPL

Thanks Neil... This is great stuff.
The ARRL has been doing some structured testing:  A very interesting article, and
links to other papers at:
http://www.arrl.org/news/stories/2003/08/21/4/?nc=1
The test vehicle looks a bit like a rolling-hamshack.
ARRL also produced a downloadable movie, w/sound, from one of their neighborhood
interference hunts.

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