On 7/7/2012 7:18 AM, W2XJ wrote:
> You got what you got. In most cases the antenna had to be adjusted for
> each channel. With DTV this is not very practical as the TV must scan
> the channels seen by the antenna at that instant.
Reception of DTV and NTSC is no different at the antenna. Channel
scanning is channel scanning and using "cut to channel" Yagis is
still "good engineering practice" in multi customer (cable, large
apartment, etc.) installations. Whether it is NTSC or DTV, the RF
signal is still analog - only the modulation is different, much like
the differences among CW, FM and SSB.
NTSC ghosting is a function of multi-path propagation and the only
way to eliminate it is highly directional antennas to reject the
reflection. However, directional antennas only work with signals
from a common direction. Due to the modulation type, DTV allows
(even requires) processing to eliminate the multipath after the
off air signal has been demodulated to its digital component this
makes antenna directivity less important but it does not eliminate
the need for sufficient gain (signal level) and directivity (noise
rejection). One reason to reject the omnidirectional antennas is
that they typically have significantly less gain and less noise
discrimination than properly designed log-periodic/Yagi hybrids.
In any case, all of this is rather far removed from amplifiers.
73,
... Joe, W4TV
On 7/7/2012 7:18 AM, W2XJ wrote:
> You got what you got. In most cases the antenna had to be adjusted for
> each channel. With DTV this is not very practical as the TV must scan
> the channels seen by the antenna at that instant.
>
>
> On 7/7/12 7:01 AM, Bill Turner wrote:
>> ORIGINAL MESSAGE:
>> On Fri, 06 Jul 2012 22:19:21 -0400, you wrote:
>>
>>> I disagree. No one in their right mind would have used an omni to
>>> receive NTSC.
>> REPLY:
>> What about those hundreds of millions of portable TVs with "rabbit ears" or
>> monopole verticals?
>>
>> 73, Bill W6WRT
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>
>
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