[opendtv] Re: 20050509 Mark's Monday Memo

  • From: Bob Miller <bob@xxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Wed, 11 May 2005 22:29:21 -0400

Manfredi, Albert E wrote:

>Mark Schubin wrote:
>
>  
>
>>    - 5th-generation LG chip in non-LG receivers - There was another test at 
>> my apartment this week.  It was
>>dramatically better than the last.  One participant characterized it as 
>>"4th-generation plus," and I won't
>>dispute that, but it didn't have the magical plug-&-play of the 
>>5th-generation LG chip in the LG box.  Notably,
>>with a loop antenna, the receiver appeared to be sensitive to people walking 
>>around the room.
>>    
>>
>
>The weird thing about this is that the 5th gen LG chip has the same smarts to 
>fight the multipath in both the LG
>box and in this new unnamed one. So the difference in performance can only be 
>attributed, one would think, to
>"the basics" of good receiver design.
>
>In the NYC environment especially, less than excellent selectivity can create 
>that intermodulation distortion
>we have seen well explained on the list, which in turn means the receiver 
>loses some C/N margin. Maybe that
>explains why any slight extra degradation of the signal, either by people 
>moving about or by a less well aimed
>loop antenna, causes the dropout of signal even when the same decoding 
>algorithms are used.
>
The LG prototype tested last summer at Mark's apartment performed as 
Mark has described. And that was all but perfect for a fixed location. 
But when we had tested it an hour before above Canal St. I should say 
that when we could position ourselves between a dual bow tie and the 
Empire State Building we could cause the receiver to fail. This was true 
when we stood in two positions to the right or left of the antenna and 
when more than one person walked around in front of the antenna.

At Mark's the antenna was mostly in the window, it was a loop and it 
seems unfased by traffic or our movements behind it in the room. We 
never were in front of the antenna AFAIR. Maybe Mark could comment.

But the point is that even the first LG prototype was easily defeated. 
Still would love to be able to get my hands on an equivalent.

Bob Miller
 
 
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