[Scan-DC] Digital tv/radio

[W4NNG]

One of the less discussed issues with 8VSB is it's sensitity to dynamic
phase shifting which may be different then the doppler problem.   It handles
what would be called ghosting on analog tv well, but if the ghosting is
shifting it's a real problem.  An airplane going over a house would cause a
momentairy shift in an NTSC picture and no loss of audio.    On ATSC is the
picture breaks and worse the audio may be loss for a second or 2.

The folks with rabbit ears are learning this with their latest generation
chip CECB's.   As long as they sit still things are fine but if anyone move
they lose the picture.


----- Original Message ----- 
From: "Jeff Krauss" <jeff at krauss.ws>
To: <scan-dc at mailman.qth.net>; <scan-dc at mailman.qth.net>
Sent: Friday, February 06, 2009 9:20 AM
Subject: [Scan-DC] Digital tv/radio


It's not exactly correct that 8VSB performs poorly in mobile environments.
The new ATSC Mobile DTV standard operates within the existing
8VSB-modulated signal, albeit with additional error correction coding
and extra training sequences to assist reception under high Doppler
rate conditions.  More information here:
http://www.atsc.org/communications/newsletter/2008_december_standard_web.pdf
and here:
http://www.atsc.org/standards/candidate_standards.php
http://www.atsc.org/standards/cs_documents/a153/S4-131r11-A153-Part-2-RF-Transmission.pdf



>------------------------------
>
>Message: 4
>Date: Wed, 4 Feb 2009 22:07:18 -0500
>From: "Andrew Clegg" <w4jecom at w4je.com>
>Subject: Re: [Scan-DC] Digital tv/radio
>To: <scan-dc at mailman.qth.net>
>Message-ID: <EOEEKJOEEAGMBNCILONKAEGDCBAA.w4jecom at w4je.com>
>Content-Type: text/plain;       charset="US-ASCII"
>
>One of the problems with the 8VSB modulation used in the ATSC digital TV
>standard is that it apparently performs very poorly in mobile environments.
>This may mean that even if a portable audio receiver ever becomes
>available,
>it may not work that well in a car, on a train, or in other mobile
>environments.
>
>A short and slightly old blog entry on the mobile performance issue is at
>http://tinyurl.com/al2ukh (but the issue is still valid since the
>modulation
>has not changed).
>
>I realize this doesn't help your friend, but it's clear that the issue of
>an
>affordable portable DTV audio receiver is probably more complicated than he
>or she thought.
>
>Cheers,
>Andy
>

______________________________________________________________
Scan-DC mailing list
Home: http://mailman.qth.net/mailman/listinfo/scan-dc
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Scan-DC at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html