Posted by Bob Miller on 01/02/06 04:27

Roy L. Fuchs wrote:
> On 31 Dec 2005 21:18:41 -0800, "G-squared" <stratus46@yahoo.com> Gave
> us:
>
>
>>BTW ghosts (multipath) are a BIGGER problem in digital than analog.
>
>
> NOT! Look up diversity receiver! Here's a sample of why NOT!
>
> Try http://www.avalonrf.com/ for just ONE player in the digital
> realm game. They are the MASTERS at signal discrimination.
>
> Just ask anyone at a race track or anyone in Hollywood, or anyone on
> the flight deck of an aircraft carrier. They ALL use diversity
> receivers.
>
> Do a search on diversity receiver(s).
>
> Either the packet makes it in, or it doesn't. The standard
> currently rests somewhere around 10% bit error rate.
>
> There's another one for you. Research "bit error rate".

>
Roy is right. In digital ghosts or multipath are a piece of cake. The
problem in the digital world of the US is 8-VSB that was never designed
to handle multipath (ghost). Others did design for it and the problem
does NOT exist, is NOT a problem in this real world.

Multipath is ONLY a problem in the retrograde political techno gunk that
is the US digital TV transition.

As your posted URL says diversity is key.

And using diversity receivers (COFDM) and a diversity network
COFDM/SFN) with "true diversity" antennas with smart receivers would be
the best way to design a modern broadcast network.

COFDM is diversity of Frequency (Coded Orthogonal Frequency Division
Multiplexing).

Using COFDM in an SFN (Single Frequency Network)is transmitter diversity.

Using COFDM with "true diversity antennas" and smarts allow for the last
leg in the best of all reception environments.

http://www.dibcom.net/us/document/Aviero.pdf
http://makeashorterlink.com/?B3065166C

A dibcom diversity receiver is being used in this video. It is attached
to the screen attached to the seat back. This receiver not only will
allow the use of up to six antennas but will add the signals from each
to one strong signal. In this video we are using two antennas attached
to the dibcom receiver. The other two videos are using single antenna
receivers.

This is also a one transmitter test. There is no SFN which would have
been even better. And the 100 Watt transmitter is at only around 400 feet.

www.viacel.com/bob.wmv

In New York City the Dibcom diversity receiver worked best when at
higher speeds when Doppler is the main culprit of decent reception.

So Roy has it absolutely right.

Multipath is NOT even a slight factor in reception with todays modern
technology. It is only a factor when using outdated technology that was
ill designed and obviously outdated.

No one in their right mind would use 8-VSB or ENG for example. ENG is
now being used in helicopters in the US to gather HD news in real time.
If multipath were a PROBLEM then this scenario surely would not work
since the helicopter is normally MOVING pretty fast and all signals it
sends would suffer from intense dynamic multipath.

They use COFDM for ENG.

Bob Miller

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