[opendtv] Re: White spaces and 700MHz D Block could be part of new US spectrum plan
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 29 Sep 2009 13:35:38 -0500
John Shutt wrote:
> What if this gizmo is working fine, but the user turned it on
> at 1 AM, after I turned off my transmitter for the night?
> (Not all stations broadcast 24/7.)
(I think all TV stations transmit through the night in this market. Even WHUT,
although those guys only transmit their logo in the wee hours. And their logo
recently went HD and wide screen. But I digress.)
What you describe would at best reduce the likelihood of interference, seems to
me.
There are several TV receivers out there that offer no more than around 22 dB
of isolation between certain most vulnerable frequency combinations, and then
33 dB or more between the less vulnerable frequencies. So if a given channel
went dark, and the gizmo took its place, at much higher power density where
your receiver is, interference could still result on *other* TV channels.
One way OTA users accommodate these receiver anomalies is by adjusting their
receive antenna(s) to achieve good reception. That only works if the
transmitters are stationary. These mobile devices coming on randomly, at random
frequencies and azimuths, cannot help but create problems when they are close
enough.
Take the antennas in my fireplace as an example. If the neighbor kids start
playing with such devices in their back yard, or even in a room facing my
fireplace, they should have very little trouble overwhelming TV signals. We
live in a valley, not within LOS of any transmitter, so the TV signals are
attenuated more than free space path loss. But those nearby mobile signals are
only attenuated as the square of the distance (free space loss).
In essence, the FCC would be playing in the hands of the MVPDs by allowing
these auto-detection devices. OTA folk would get disgusted and cave in.
Just like the FCC did when they mandated unbundling of the telco xDSL lines. It
discouraged telcos from installing these lines, and cable had a broadband
monopoly for several years.
Bert
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