[opendtv] Re: 20040722 Thundering Thursday Thanks (Mark's Monday Memo)

  • From: Eory Frank-p22212 <Frank.Eory@xxxxxxxxxxxxx>
  • To: "'opendtv@xxxxxxxxxxxxx'" <opendtv@xxxxxxxxxxxxx>
  • Date: Fri, 23 Jul 2004 11:50:21 -0700

>> The most amazing thing was the obvious superiority of the simple loop
>> and rectangular antennas.

>Indeed. I suspect two problems. First, I wonder if the active antennas
>introduce some extra phase distortion, or other type of distortion,
>that was imperceptible with analog TV? Second, the more directional
>indoor antennas probably do work better at pulling in weak stations,
>but obviously not without being re-aimed. If you're looking for an
>antenna that mustn't be touched between stations, the less directional
>the better.

If you want to constructively add multiple signals, then the less directional 
antenna is superior. It may be that the "principal ray," if there is one, does 
not have enough SNR to meet threshold, so a narrow beamwidth antenna that 
selects only this ray does not result in reception. But an omni or much less 
directional antenna like a loop can collect energy from a multitude of 
different signals, that when constructively added, exceed the threshold SNR 
with margin to spare. These less directional antennas have the added advantage 
that they don't need to be re-aimed, or at least require much less re-aiming, 
to receive all available broadcasts.

This sounds like the familiar COFDM "trick" of using multipath to your 
advantage. Lynx demonstrated that it was also possible to do this with 8-VSB. 
Now perhaps LG is demonstrating this principle yet again. They are 
well-deserving of congratulations, not only for demonstrating that excellent 
8-VSB reception is possible, but for actually building a real chip that can be 
used in actual consumer products.

-- Frank
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