[HATS] Re: DTV

[KB9FOHAM@aol.com]

Europe uses a COFDM system with 8 MHz bandwidth to fit their old PAL 
bandwidth channels.  There are several versions of COFDM including various 
bit rates and # of carriers. The system most likely to survive is an adaptive 
bandwidth system that can provide "low def" but visible pix on just the "most 
significant bits" and high def if it gets all the data.  there is so much 
error correction and digital manipulation going on its near impossible to 
know what you are seeing unless you  can analyze the decoder activity.  The 
test gear costs over $250,000 to test any of this stuff and find out why it 
works or doesn't. Its the most difficult testing I have ever done. Even the 
testing is difficult with all the right equipment. It is unbelievably 
complicated and at best it takes 2 hours per site to test DTV vs 15 seconds 
to test NTSC. 
I'm using my personal former ENG van stocked with equipment floor to ceiling, 
4 computers, vector signal analyzer, scopes, spectrum analyzer, special demod 
with tap energy displays, ghost (time delay) measurement, signal level 
measurement, bit error rate, and much more.  No TV store is going to have 
this stuff to tell "Joe six pack" why he isn't getting channel A, N, C, F or 
whatever. The receivers so far have no helpful tuning guide either. The 
development stage is more akin to 120 line vertical scanning with Nipkow 
disks that it is a working system. Not to mention that virtually nothing is 
reliable. Just changing antennas is a complete toss up of any "standards" and 
calibrations. Its a nightmare.   By the time the testing is done I will 
likely be one of 10 people in  the world that will know what the real truth 
is about DTV. 73  Henry AA9XW




The New KGB:
Klinton,
Gore, 
Janet "Bang" Reno.
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