[opendtv] Re: DVB-T HDTV demo using 19.7 Mbps in a 6 Mhz channel in costa rica
- From: Doug McDonald <mcdonald@xxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 06 Mar 2006 11:19:44 -0600
John Shutt wrote:
> Doug,
>
> Thank you for confirming that atmospherics will cause more than a 2 dB
> difference in the received signal.
>
> John
More than 2 dB?? Of course more than 2 dB ... it's more like
20 or 25 dB!!!
HOWEVER ... its seasonal. In stable seasons it can sit
stably for weeks. Only in late summer or fall do you see
frequent sharp upward spikes of up to 25 dB. Only in early
winter do you see the small but significant downward dips.
And as I said, a 2 dB difference in signal power from the
transmitter makes a DRAMATIC difference in the useability of
a station in the presence of these fluctuations.
The fact that there are fluctuations due to tropo conditions
is a reason why a 2 dB difference DOES matter, not why it
does NOT matter. THAT'S MY POINT, in the real actual world.
Doug McDonald
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