[opendtv] Re: News: FCC Floats Cash-For-TV-Spectrum Scheme
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 31 Oct 2009 08:37:27 -0400
At 3:25 PM -0500 10/30/09, Manfredi, Albert E wrote:
>
The RF energy density is far more uniform and at lower power
levels that the big sticks.
Are you kidding me?
The power density impinging on people using hand-held phones, with
transmitter inches from their bodies, is much greater than big
sticks create, unless you're very close to the big stick.
Come on Bert, don't change the subject. Yes, holding a transceiver
close to your head does increase the energy density locally; this is
somewhat analogous to CRT TV displays, for which we were warned not
to sit too close because of X-ray emissions.
http://en.wikipedia.org/wiki/Cathode_ray_tube#Health_concerns
The subject of this discussion was RF levels in the environment and
the power needed to create these levels of RF. There have been
multiple legal battles around the country, brought by NIMBY home
owners who did not want to live in the high RF fields near TV
transmitters.
No such equivalent with Cell and SFN towers, other then fighting them
because they are often eye-sores.
You must look at the energy density of a big stick based on
distance from that stick.
So do so, Craig. Give me numbers.
The big stick is 1 MW, transmitting at 600 MHz.
The hand-held is 100 mW, also at 600 MHz.
The big stick is 1 Km away, i.e. very close for a big stick, and the
hand-held is 5 cm away.
The power received by a receive antenna at your location from the
big stick is +2 dBm. Increase the distance to the big stick to 2 Km,
and the power at the receive antenna is -4 dBm.
The power received from the handheld is +18 dBm!
See the difference? What kind of silly hype would pretend that
hand-held devices are green?
Apples and Oranges Bert.
The only concession I will make is that it is likely that any mobile
TV SFN receiver may ALSO be a packet data transceiver in the future.
So when the device is close to your head, yes the energy density
increases (for the transmitter, not reception). This is far different
than high RF levels in the ambient environment, which is what we were
discussing.
Regards
Craig
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