[opendtv] Post on alt.tv.tech.hdtv of interest today
- From: Bob Miller <bob@xxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 04 Apr 2005 15:59:04 -0400
BTW I am still having my calls to broadcasters returned.
Key interest seems to be the need for MPEG4 and receiver standards which then
opens the door to consideration of looking at modulation.
Bob Miller
On 4 Apr 2005 11:18:53 -0700, "inkyblacks@xxxxxxxxx"
<inkyblacks@xxxxxxxxx> wrote:
>>There is no way in hell Congress is going to spend 10 billion dollars on a
>>digital transmission subsidy. I would guess 2 billion at most.
>>They want to make money selling off the dead airspace, not lose it to people
>>who can afford to buy new TVs or cheap adapters. The adapter
>>boxes can be $80. each or less. 2 billion buys allot of them. Even most
>>people on welfare have cable and don't use their OTA analog
>>receivers anyway.
>
>
No way in FUCKING hell is the US going to switch. COFDM is not a feasible
technology for US DTV transmissions. Period.
Besides COFDM's major/fatal impulse noise problem.. Which in turn results
in a major power problem.
It also as a significant adjacent channel interference problem. I.E.. COFDM
uses 5.7Mhz out of a 6Mhz frequency assignment..
8VSB uses only 5.3Mhz out of 6Mhz..
Thus COFDM transmissions interferes with US NTSC transmissions on adjacent
channels. (P.S.. This type channel allocation happens in
nearly every major market.. )
Oh.. increasing the COFDM power to overcome impulse noise issues, only makes
the adjacent channel interference problem worst..
This aspect also precludes.. Bob's many transmitter tower approach.. Since
existing NTSC broadcasts occur from single towers..
Mixing in many smaller transmitter towers creates zones of increasing cross
channel interference. (COFDM near the smaller towers
interferes with NTSC transmission being broadcast by a more distance
transmitters.. )
Additionally... SFN (on channel repeaters) encounters significant problems
when you go over 38km main tower.. (Side lobes from repeater
signal and main transmission lobe start canceling out) In the US, COFDM
quickly run's out of available channels without a viable SFN.
(P.S. Neither the UK nor Oz currently use SFN COFDM repeater schemes.)
That's three FATAL strikes against COFDM in the US.
1. Power/impulse noise/range..
2. Interference with existing NTSC broadcasts on adjacent 6mhz channel
assignments.
3. Insufficient # of free channels to implement. (non-viable SFN
capability..
Now you can try too imagine deploying a DTV system without a valid
transitional scheme... But it ain't going to happen in the real
world.. no way ... no how.. end of story..
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