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An engineer witness reports on the crime

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Anonymous
April 22, 2004 9:44:45 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

A PBS engineers witness of the "far field" difference between COFDM and
DVB-T in the real world. Hint there is none. His conclusion...

" In the fringe areas (far field or a long ways away), 8-VSB and COFDM
performance was virtually equal. In the majority of urban test sites, COFDM
worked well, while 8-VSB did not work at all."

http://web-star.com/hdtv/pbsbalit.html

COFDM AT A DISTANCE
by

Jan Pazral,
Chief Engineer
WXXI Public Broadcasting Council

August 11, 1999

Jan Pazral is the chief engineer at a public television station, and a
member of the engineering advisory group to APTS (America's Public
Television Stations). Since those PBS engineers who first observed the
Baltimore tests were unable to observe distant reception tests, we
encouraged Jan to try to see this in his subsequent trip. His report is
notable in his observations of two remote sites. His report is posted with
permission.

Regards,

Bruce Jacobs
KTCA, St. Paul

----------------------------------------------------------------------------

As most of my colleagues in the broadcast industry, I took 8-VSB as
given. This issue has been decided long time ago and explained to us on
various DTV
seminars, workshops and conferences. The term Longley-Rice has become as
familiar to us as NTSC or Subcarrier. We were told that DTV, while not as
easily receivable as NTSC, will replicate the analog coverage by simply
using adequate outdoor antennas. Then recently, it came to my attention that
field tests in urban areas, using current generation of consumer DTV
receivers and consumer antennas, revealed serious problems with 8-VSB
reception and, moreover, receivers using COFDM, a modulation method the
only thing I knew about was that it existed, provided solid reception
most of the
time. This issue became a topic of discussion at the conference call of
the APTS Engineering Advisory Group in mid-July where testimonials from
engineers who eyewitnessed the tests confirmed that the 8-VSB
transmission could not be received in densely populated areas just a few
miles from the
transmitter. I realized that in order to participate in the Advisory
Group discussions on this issue in a meaningful way, I needed to see the
tests for
myself. I took the opportunity to travel to Baltimore and observed the
field testing on August 3. The purpose of my trip was not gathering a
collection
of scientific data and compiling a list of decibels and bit-rate errors.
I wanted to find out what kind of reception an owner of a consumer DTV
receiver can expect in urban, suburban and rural settings.

The following equipment was used for reception and testing:

ATSC Receivers (8VSB):
Panasonic TU-DST50
Pioneer Elite SH-D500
DVB-T Receivers (COFDM):
Nokia View Master 9600
NDS System 3000
HP Spectrum Analyzer
Antennas:
Bow-tie dipole
Double bow-tie with reflector
13-element Yagi antenna
Winegard pre-amplifier
RF switches and RF attenuators
6-foot antenna mast
(On that particular day, Geocast Corp. was testing an 8-VSB prototype
receiver board made by Oren Semiconductor. This receiver did not have a
video output; it was interfaced to a laptop computer instead.)

The following equipment was used for transmission:

Comark IOT transmitter
Two-panel antenna, 1200 ft HAAT, 50 kW ERP
Zenith 8-VSB modulator (19.39 Mbps)
Rohde & Schwartz SFQ COFDM modulator (3/4 FEC, 1/8 Guard, 1705 total
carriers, 18.662 Mbps)

The testing started at 9:45 EDT at the DTV Channel 40 / NTSC Channel 45
transmitter site near 2000 West 41st Street in Baltimore. The performance of
all receivers was verified by a direct connection to a padded tap on the
transmission line. I will not go into a great detail about the data
collected here. I just mention that the RF threshold for the Pioneer
receiver was -82dBm, for all others about -78 dBm. The reference power for
the spectrum analyzer was -22 dBm for both 8VSB and COFDM. Subjectively,
all receivers worked well.

The location of the first test site was in Downtown Baltimore, Lombard
at Greene Street. While the spectrum analyzer showed strong and
reasonably flat
RF signal using any of the three antennas (we tried aiming them in
different directions), none of the two 8-VSB receivers produced any
video. The OREN
receiver did not establish a lock either. Having the bow-tie antenna on
a stick in my hand, I was unable to find a spot within a reach of the
antenna
cable where 8-VSB would work. The COFDM reception was a different story.
While the RF signal on the spectrum analyzer looked virtually identical,
receivers locked instantly. Again, walking around with a bow-tie dipole
antenna in my hand, it was hard to find a spot where the reception would not
work. Even then, the disturbance was limited to an occasional glitch,
rather than a complete loss of signal.

The second site was on the top level of the parking garage of BWI
airport. The transmitting antenna was clearly visible. All receivers worked
flawlessly using a bow-tie dipole.

The third site, an open parking space randomly found at the bottom level
of the same parking garage, was a tough spot to receive UHF. Analog
reception
of channel 45 was ghosty and noisy. There was no 8-VSB reception using
any of the three test antennas. There was, however, solid, glitch-free COFDM
reception using the double bow-tie antenna. The difference in quality
between the COFDM and analog reception was so dramatic that if I was a
viewer having the same conditions, I would gladly pay for a COFDM
receiver to achieve that level of picture quality.

The last two sites were distant sites, picked on-the-fly. In Waldorf,
MD, 48.8 miles from the transmitter site (distance measured be a GPS
instrument), we were able to receive both COFDM and 8-VSB using
13-element YAGI. There were several interesting things about this site:
Adjacent DTV
channel 39 out of Washington D.C. was about 15 dB stronger than channel
40. The site was next to a busy road and antennas were aimed across the
road.
There were trees in the direction of the transmitter about 200 to 300 ft
away and there were airplanes crossing the RF signal path. My observation
was that both 8-VSB and COFDM signals were receivable at this location.
The aim and location of the antennas for 8-VSB reception was much more
critical
than that for COFDM. The road traffic did not seem to have any effect on
either 8-VSB of COFDM, but the airplanes flying overhead produced
considerably more disturbance to 8-VSB than to COFDM.

The fifth and last test site was Mechanicsville, MD, 62.2 miles from the
transmitter, outside of the grade B contour. I had the opportunity to select
the test point myself. This test site was located about 200 ft from a
busy divided highway, about 150 ft from a parking area with two idling
diesel
trucks and about 250 ft from a gas station. Using the single bow-tie
antenna with a pre-amp did not provide a satisfactory reception on any
available
receiver. Subjectively, there were slightly more glitches using COFDM
than using 8-VSB. The 13-element YAGI and the double bow-tie with reflector,
however, produced solid, glitch-free reception for both COFDM and 8-VSB.
(The aiming of the Yagi was not critical reception was maintained within ±
40 degrees for both systems.)

Based upon my observations I came to the following conclusion: The
Baltimore tests are believable. I was favorably impressed with the
methodology and the
documentation of those tests. In the fringe areas, 8-VSB and COFDM
performance was virtually equal. In the majority of urban test sites, COFDM
worked well, while 8-VSB did not work at all.

We can expect spotty 8-VSB reception in other urban areas elsewhere in
thecountry.

While there may be advancements in the receiver technology, 8-VSB (based
on single carrier and high data rates) in multipath environment will pose
greater challenge to receiver manufacturers than COFDM (based on
multiplecarriers and low data rate).

Jan Pazral,
Chief Engineer
WXXI Public Broadcasting Council
April 22, 2004 11:38:27 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Bob Miller" <robmx@earthlink.net> wrote in message
news:hZIhc.6572$e4.5013@newsread2.news.pas.earthlink.net...
> A PBS engineers witness of the "far field" difference between COFDM and
> DVB-T in the real world. Hint there is none. His conclusion...


"My argument against 8-VSB is purely personal...". -Bob Miller, 8-11-03
alt.tv.tech.hdtv
Anonymous
April 22, 2004 12:04:54 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

On Thu, 22 Apr 2004, David wrote:
> "Bob Miller" <robmx@earthlink.net> wrote in message
> news:hZIhc.6572$e4.5013@newsread2.news.pas.earthlink.net...
>> A PBS engineers witness of the "far field" difference between COFDM and
>> DVB-T in the real world. Hint there is none. His conclusion...
> "My argument against 8-VSB is purely personal...". -Bob Miller, 8-11-03
> alt.tv.tech.hdtv

Note that the memo that Miller dredged up is dated August 11, 1999 -- as
if everything remained the same in the intervening 4 years and 9 months.

This is just like the silly NTSC vs. PAL debates of a few decades ago.
Lots of so-called "experts" babbling "Never Twice the Same Color" and how
PAL was superior looked pretty stupid with the advent of TV sets with
decent electronics. All of a sudden, green and purple faces were gone
from NTSC, but the headache-inducing flicker in PAL was not.

-- Mark --

http://staff.washington.edu/mrc
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.
Related resources
Anonymous
April 22, 2004 2:28:05 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

On Thu, 22 Apr 2004, Bob Miller wrote:
> I am particularly excited by Japan and Italy. Japan has sold over a million
> HD receivers in just the first few months of broadcasting

Japan has tried repeatedly in the past 15 years or so to get a working
HDTV system. Their first attempt was an analog system which failed
miserably.

Maybe this time they'll get something which works for them. But even if
they do, it won't be of much interest for North America. Japan is an
highly-mountainous archipelago, with only about 18% of the land being
usable. The population is clustered in small and very densely populated
urban areas. People in Japan think of such-and-such place being very far
away, but when you look at a map you see that it's only 10 miles as the
crow flies. There is nothing like suburbia as we know it in North
America.

COFDM probably works well in that type of dense concrete jungle. That
isn't the case in most of North America.

-- Mark --

http://staff.washington.edu/mrc
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.
Anonymous
April 22, 2004 7:49:08 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

Bob Miller (robmx@earthlink.net) wrote:

: COFDM AT A DISTANCE
: by

: Jan Pazral,
: Chief Engineer
: WXXI Public Broadcasting Council

: August 11, 1999
^^^^^^^^^^^^^^^

Ancient history.

Yawn.

-bruce
bje@ripco.com
Anonymous
April 23, 2004 12:08:08 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

David wrote:

> "Bob Miller" <robmx@earthlink.net> wrote in message
> news:hZIhc.6572$e4.5013@newsread2.news.pas.earthlink.net...
>
>>A PBS engineers witness of the "far field" difference between COFDM and
>>DVB-T in the real world. Hint there is none. His conclusion...
>
>
>
> "My argument against 8-VSB is purely personal...". -Bob Miller, 8-11-03
> alt.tv.tech.hdtv
>
It is! So?

Personally I think that it is an outrage that our government which is
supposed to have our interest at heart sold us out.

As a business person however I pray every day that broadcasters are
FORCED to stay the course with 8-VSB. As long as they can not do
mobile/portable they can't compete.

Now comes the conflict. As long as 8-VSB hinders the transition there is
a roadblock called incumbent broadcasters who squat on spectrum already
sold for other uses. Those uses include HDTV BTW.

And while our plan does include delivering HD to buses and trains
including advertising, it also includes a lot of other good stuff. And
our plan isn't the only one.

The digital transition is being held up by those who now have
monopolies. It is in their interest to keep spectrum out of the hands of
competitors. This is why both broadcasters and wireless telcos did and
were successful at keeping this spectrum from being used till now. They
don't want to have to bid for it and don't see a crying need for it at
the moment so the next best thing is to just impede its use by others
for as long as possible.

And they are really good at it. I often wonder if those who post against
my post work for LG or a broadcaster or the NAB. I doubt it however
since they are usually just personal attacks. Can't remember the last
good critic. If I thought I was having such an affect I would have to
stop anyway. Wouldn't want to actually get rid of 8-VSB.

So personally I am for COFDM or any rational modulation and I am trying
to sound the alarm (since 1999) that should be apparent to anyone by now
that the use of 8-VSB would fail, is failing and will continue to fail.
Business wise I want 8-VSB to stay around and I want the transition over.
Anonymous
April 23, 2004 12:08:09 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Bob Miller" <robmx@earthlink.net> wrote in message
news:ICVhc.7219$e4.1540@newsread2.news.pas.earthlink.net...

> And while our plan does include delivering HD to buses and trains
> including advertising, it also includes a lot of other good stuff.

Please tell us about all the other good stuff in your plan.
April 23, 2004 12:08:09 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Bob Miller" <robmx@earthlink.net> wrote in message
news:ICVhc.7219$e4.1540@newsread2.news.pas.earthlink.net...
> David wrote:
>
> > "Bob Miller" <robmx@earthlink.net> wrote in message
> > news:hZIhc.6572$e4.5013@newsread2.news.pas.earthlink.net...
> >
> >>A PBS engineers witness of the "far field" difference between COFDM and
> >>DVB-T in the real world. Hint there is none. His conclusion...

> > "My argument against 8-VSB is purely personal...". -Bob Miller, 8-11-03
alt.tv.tech.hdtv
> >
> It is! So?

Purely personal, as in lining your pockets?

Why did you argue with engineering people about the advantages of COFDM?
I've seen you lose hundreds of arguments over the years.
You repeatedly display ignorance about your own cause.
You can't think clearly on the subject, because it's an emotional issue for
you.
Anonymous
April 23, 2004 1:20:01 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

On Fri, 23 Apr 2004, Bob Miller wrote:
> Our digital TV transition is on the
> life support of a MANDATE that is about to kick in

So you are claiming that the European governments did not impose a mandate
for COFDM?

-- Mark --

http://staff.washington.edu/mrc
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.
Anonymous
April 23, 2004 5:34:23 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

David wrote:
> "Bob Miller" <robmx@earthlink.net> wrote in message
> news:ICVhc.7219$e4.1540@newsread2.news.pas.earthlink.net...
>
>>David wrote:
>>
>>
>>>"Bob Miller" <robmx@earthlink.net> wrote in message
>>>news:hZIhc.6572$e4.5013@newsread2.news.pas.earthlink.net...
>>>
>>>
>>>>A PBS engineers witness of the "far field" difference between COFDM and
>>>>DVB-T in the real world. Hint there is none. His conclusion...
>
>
>>>"My argument against 8-VSB is purely personal...". -Bob Miller, 8-11-03
>
> alt.tv.tech.hdtv
>
>>It is! So?
>
>
> Purely personal, as in lining your pockets?
>
> Why did you argue with engineering people about the advantages of COFDM?
> I've seen you lose hundreds of arguments over the years.
> You repeatedly display ignorance about your own cause.
> You can't think clearly on the subject, because it's an emotional issue for
> you.
>
>
No Dave if you read all those post you would have read that I am arguing
against my own self interest. If broadcasters could use COFDM there
would be little room for a mobile service by someone else. 8-VSB the
failure breeds opportunity.

The only argument I am having is over the merits of 8-VSB and whether it
will survive. I think so far I an winning. Our digital TV transition is
on the life support of a MANDATE that is about to kick in and faith in a
miracle receiver due in 2006 or over SIX years since the controversy
started. Even if in 2006 8-VSB became a raving success the intervening 6
year delay would still count as a massive failure. 8-VSB is already a
failure no matter the future.

One aside. Do you know that more IP for COFDM is American and that most
IP for 8-VSB is S. Korean? The basis of COFDM was invented by Bell Labs.

BTW do you have a list of all those arguments I have lost so I can keep
track of them?
April 23, 2004 7:18:24 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Bob Miller" <robmx@earthlink.net> wrote in message
news:zo_hc.5710$eZ5.4239@newsread1.news.pas.earthlink.net...
>
> BTW do you have a list of all those arguments I have lost so I can keep
> track of them?

Every one of them is available for viewing.
Do a search in Google (groups).
This is how I've found all the current COFDM/interference complaints from
England and Australia.

Try a search for your name (in quotes), COFDM, and "LIAR" and you'll see
about 25,000 postings over the last 6 years.
April 26, 2004 5:35:37 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

Short and to the point. Bob get over it. They are not going to change
standards now and bitching ain't gonna help. Maybe they should have
used a different standard but, they didn't. Remember shoulda, coulda,
mighta and aughta are some of the biggest words in the english
language, cause hidsight is always 20/20. Do us all a favor and give it
a rest dude.
!