Multipath question

Archived from groups: alt.tv.tech.hdtv (More info?)

It depends upon your definition of "main signal".

I used to have a situation where the signal reflected off a nearby hill
was stronger than the direct path signal which had to diffract over a
different hilltop. So you had a weak direct path signal, followed by a
stronger reflected signal. Which was the "main signal"?

Maxwell wrote:
> DTV has been designed to operate in the presence of signal reflections up to
> certain amplitudes and delays relative to the main signal. I have seen
> reports on the Web about indoor DTV tests where reflections were measured
> both to lead and lag the main signal by up to tens of microseconds.
>
> Does anyone know how reflections could lead (arrive before) the main signal?
> Seems strange that the main signal (strongest signal) wouldn't be the most
> direct path and therefore have the shortest propagation from the
> transmitter.
>
> Maxwell
>
>
>
>

Archived from groups: alt.tv.tech.hdtv (More info?)

"Maxwell" <nospam@nospammmmm.com> wrote in message
news:fqKRd.1536$DC6.53@newssvr14.news.prodigy.com...
> DTV has been designed to operate in the presence of signal reflections up
to
> certain amplitudes and delays relative to the main signal. I have seen
> reports on the Web about indoor DTV tests where reflections were measured
> both to lead and lag the main signal by up to tens of microseconds.
>
> Does anyone know how reflections could lead (arrive before) the main
signal?
> Seems strange that the main signal (strongest signal) wouldn't be the most
> direct path and therefore have the shortest propagation from the
> transmitter.
>
> Maxwell
>

One example is Cable TV where the strongest signal is behind the direct
signal from over the air. Another is a poor signal area (in a valley be it
natural or man made) where the best (signal strength) signal is a reflection
off a building.

Your logic is correct but when thinking about signal, you are looking for
best signal not direct in some cases.