[opendtv] Re: 20050627 Mark's Monday Memo
- From: "John Willkie" <JohnWillkie@xxxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 1 Jul 2005 21:04:44 -0700
Just yesterday, I was talking with an engineer from KABC while I attended a
Triveni digital seminar. He was amazed with what they could away with using
COFDM relays, particularly in the short distances. KABC also has the second
US HDTV camera in a helicopter (KUSA Denver has the first). It provides
great pictures. However, he told me that it doesn't reach long enough --
the only helo receive point with cofdm is Mt Wilson -- and there are many
places where they just can't get good pictures. I'd provide the engineer's
name, but I don't have his permission.
That's almost the exact opposite of the 'running out of long island'
comment. The distances you gave for relative points seems smaller than the
county of Los Angeles; and the LA market is more counties than just LA.
Funny enough, the terrain you describe is almost completely flat -- a bit or
moraine on Long Island, and you didn't mention points to the West of the
city.
Mt Wilson is 5800 or so feet above mean sea level -- there are few manmade
obstructions that can get in the way of a helicopter operating under normal
conditions. There is a tremendous amount of terrain obstacles throughout
the region. Temperature inversions are also common, with multiple
temperature layers between the valley floors and the mountaintops. These
can tend to deflect or duct signals, depending on a variety of factors.
By the way, this is more an apples to apples comparison than to compare
omnidirectional broadcast (half power beam width >180 degrees) against
microwave Intercity relay (half power beam width <4 degrees. . But, of
course, it's not about the engineering to this particular OFDM proponent;
it's about the ability to rail here against imagined enemies, and to
"support" an impossible idea -- COFDM competing with 8-VSB -- with any
opening he's given.
Speaking of that, I did espy the channel 55 Qualcomm MediaFlo equipment
room (more room than equipment right now) and the LA-101B terrestrial relay
point for XM Radio atop Mt Harvard yesterday. Can't wait to see what unique
non-porn content is distributed by the Qualcomm system.
John Willkie
----- Original Message -----
From: "Bob Miller" <bob@xxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Friday, July 01, 2005 3:41 PM
Subject: [opendtv] Re: 20050627 Mark's Monday Memo
> Eory Frank-p22212 wrote:
>
> >John Willkie wrote:
> >
> >
> >
> >>Frank
> >>
> >>I'm suprised about your assertion re far-field. There are members of
this
> >>list who routinely send a single ATSC hop -- to serve translators --
that
> >>are several hundreds of miles in length. One is doing this every day in
> >>Arizona, on a station that you routinely watch -- assuming you watch
PBS.
> >>There are NTSC hops of more than 225 miles, with the termination point
in
> >>Arizona.
> >>
> >>
> >
> >I don't dispute what you say about single ATSC hops today. But my
'assertion' re far-field was not an assertion but rather a request for
someone to provide some honest data that compares 8-VSB and COFDM far field
reception under equal conditions. The reason is quite simple: the industry
has been sold on the idea that 8-VSB is superior to COFDM in reaching the
far-field viewers that our common in our country, with our big-stick
broadcast infrastructure. The implication is that somehow this 'advantage'
helps negate the obvious disadvantages 8-VSB has in high multipath urban
areas.
> >
> >
> >
> >>Is there a COFDM hop in existence that exceeds 60 miles? I'd be
interested
> >>in hearing about those long COFDM hops in Australia.
> >>
> >>
> >
> >Whether there is or not, I'd also be interested in hearing what ERP's
they use in Australia vs. the U.S. Apples vs. apples is all I ask.
> >
> >About all we have to go on is old tests and/or anecdotal observations,
like the one John Shutt forwarded earlier from a PBS engineer who in August
1999 wrote:
> >
> >"In the fringe areas, 8-VSB and COFDM performance was virtually equal."
> >
> >
> >-- Frank
> >
> >
>
> As far as single COFDM "hops" using COFDM ENG here in New York City an
> engineer told me of "running out of Long Island" without losing a mobile
> helicopter ENG connection to his studio back in Manhattan on the East
> Side of 42nd St. He had the same experience going in the other direction
> to the Delaware Water Gap and down to Atlantic City.
>
> The distances here are Montauk 120 miles, Delaware Water Gap 75 miles
> and Atlantic City 133 miles.
>
> Bob Miller
>
>
>
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