[opendtv] Re: 7" ATSC TV
- From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 17 Apr 2007 09:51:22 -0700
Bert wrote:
> However, the unlicensed device may be a signal null, and even if
> low powered, it will clobber any nearby receiver tuned to that
> channel. This is painfully predictable, and no tuner design will
> solve the problem.
Agreed, there is little or nothing a receiver manufacturer can do to
overcome co-channel interference. Preventing this from occurring is the
responsibility of the unlicensed device manufacturers, who assure us that
the problem will not occur in their designs...generally I expect this is
true but there are clearly exception - one which you pointed out.
Another major flaw is when the DTV viewer is using a 30 ft. (or lower) mast
mounted antenna* to receive the markets DTV services while the unlicensed
device is setting on a desktop next door. The device, which is required to
automatically scan for unused channels before transmitting, will likely not
"see" all channels picked up by the mast mounted antenna, a major flaw in
the design concept.
However, the main issue that receiver design can/must resolve is the
interference caused by the unlicensed devices lighting up on the problematic
adjacent channels. This infraction is much more likely to occur and there is
only one practical solution: the receiver RF section must be design to
operate in this environment, which also exists without the introduction of
these new devices and is an issue generally unaddressed by A/74.
* = The 30 ft. mast mounted antenna is part of the FCC criteria for DTV to
duplicate analog coverage, therefore that option must be protected when
authorizing any new service in that spectrum.
Dale
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