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Re: HDTV WONDER?? Purchasing a outdoor UHF antenna.

Posted by Doug McDonald on 01/01/06 18:47

Roy L. Fuchs wrote:

>>
>>Multipath *IS* a problem for digital in situations where you don't have
>>line-of-site and the desired vs. undesired signals are approximately equal
>>in strength. In areas where the desired signal is at least 3 db stronger
>>than the undesired signal then it is normally of no consequence except
>>when you're using a directional antenna (with or without a rotator) and
>>have it aimed at the wrong signal or when unusual atmospheric conditions
>>(inversions and tropo ducting) are present.
>
>
>
> Most, if not all HDTV broadcast signals get assigned to channel slots
> that are exclusive to that broadcaster and locality. Usually an
> unassigned UHF slot. You circumstance should never be confronted,
> much less be a problem.



Mr. Fuchs, you are just plain underinformed.

Most certainly an ATTEMPT was made to assign DTV stations to
channels where nearby (in space) co-channel stations did not exist.

This was mostly successful in say, Wyoming. It was an abysmal
failure NE of a line from about Detroit to Washington DC. That's not to
say that you might not find some stations in New Your that don't have
co-channel interference problems, but there are many stations that
have very bad co-channel problems, especially in the late summer and
fall when tropo propagation of UHF is strongest. It's a real problem,
a severe problem, and in many cases there is no cure with
better antennas, since the desired and undesired stations are
in the same direction.

And adjacent channel interference is also sometimes a problem:
it's true here in central Illinois in one case.

And it would be a worse problem ... three dB worse ... had
we used COFDM.

Doug McDonald

 

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