[opendtv] Re: DVB-T HDTV demo using 19.7 Mbps in a 6 Mhz channel in costa rica
- From: Bob Miller <bob@xxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 06 Mar 2006 12:52:30 -0500
Manfredi, Albert E wrote:
>John Shutt wrote:
>
>
>
>>>"...the field this difference shrank to 2 dB. Sinclair
>>>suggests that this may be due to the effect of real
>>>world impairments that add to the theoretical 'gaussian'
>>>channel values."
>>>
>>>
>>What is the point of your quote? It reinforces what was
>>actually observed in the field by over a hundred different
>>observers over the course of a summer in 1999. You think
>>you can tell the difference in 2 dB of sensitivity in your
>>living room with your receiver?
>>
>>
>
>You didn't pay attention to the last sentence, John. Let me paraphrase:
>
>"The reason the theoretical C/N advantage was not witnessed in the field
>was probably due to some level of multipath, which degrades 8-VSB
>reception to less-than-gaussian levels of performance. In early
>receivers, these impairments degraded the C/N margin in 8-VSB
>significantly. With better demods, the expectation would be that the
>theoretical C/N advantage in 8-VSB would be restored."
>
>Watching the excellent signal monitor in the Accurian/Digital Stream
>boxes, which includes an SNR display, I can say that a 3 dB difference
>is not to be ignored. And also, that the 15 dB number is predictable and
>achievable, not theoretical or rare.
>
>And it's far better to read and understand reports rather than despair
>based on faulty assumptions.
>
>Bert
>
We are still waiting for those better 8-VSB receivers Bert and I for one
will put any COFDM receiver up against them. So far anything that 8-VSB
can do that can be received by any generation of receiver including the
prototype is a piece of cake for any COFDM receiver which will run rings
around it. And yes at any distance.
We are not talking here about theoretical 8-VSB receivers that may be
developed that will obsolete current 8-VSB receivers are we? That is the
same thing as a new modulation in my book. If and when we get to that
steam it will make sense to test all current or potential new
modulations before picking a one. Any new version of 8-VSB should also
be considered.
Bob Miller
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