5/18 Has anyone tested the range of those 2.4 GHz cordless phones? My
home is less than a mile away from my office. Yes, I'm serious.
\_ Why don't you just forward your calls to your office.
\_ why would you want to broadcast your telephone conversations
to anyone within a mile radius who happens to own a cheap
scanner?
2.4 GHz cordless phone?
\_ I'm no RF expert but I never understood why higher frequency
\_ Can cheap scanners decode transmissions from a typical
2.4 GHz cordless phone? The answer is no.
\_ you're not RF expert *BUT* you don't understand?? what the
hell does that juxtaposition mean?
\_ I'm no RF expert so I never understood why higher frequency
means greater range.
\_ E =hv ??? more energies?
\_ you're confusing equations. this is for a single particle. you
can transmit a 10khz signal and give it just as much energy
as a 10Mhz signal by uppingthe amplitude (or the intensity,
if you like particles). i'm no RF expert either, but I think
the answer is that wavelengths get interference from objects
of similar size. there are lots of large obstacles, so low
frequencies don't perform well, and there are lots of very
tiny obstacles, so light and doesn't do well, but somewhere
in between, you get good shit. -ali
\_ Stupid fuzzy universe. Why wasn't Planck's constant set
to 0, damn it!
\_ ali, or someone else with clue, please explain to me
why IR tends to bounce around, but microwave is
directional
\_ AFAIK, it is just as ali said--that is, your wall will
absorb and re-emit the IR. IR is very close to the
visible spectrum in wavelength whereas microwave further
away. The physical transitions for visible and infrared
are similar, whereas microwave is different. Hence
materials that reflect visible light will likely reflect
infrared the same or nearly the same way. See
http://www.scimedia.com/chem-ed/light/em-spec.htm for a
spectral breakdown. -emarkp
\_ Huh? All you said was that IR is like visible
and microwave is different. Why does IR tend
to bounce around, but microwave tend to be
directional?
\_ It bounces around for the same reason that visible
light bounces around. Absorption and reemission.
\_ Now what about microwaves?
\_ Microwaves are caused by molecular rotations,
instead of electron level jumps. That's why
it makes stuff hot--it rotates/vibrates water
molecules, and the friction warms up the
food. Broadcast microwaves have shorter
wavelengths yet and ignore most atmospheric
matter. Since the matter (in the air or in
your wall) isn't the right size to absorb the
energy, it just goes right on by.
\_ Different wavelengths definetly have different absorption
and reflection properties. However, I don't think
a 2.4 GHz signal has a longer range because of less
reflection/absorption. A 2.4 GHz can bounce off
walls and buildings pretty easily. One possible reason
for the longer range of a 2.4 GHz signal could be higher
bandwidth. I think the FCC allows 80 Mhz of bandwidth
for 2.4 GHz signals, but don't know the numbers for
other frequencies. Also there might be less interference
in the 2.4 GHz band than in other bands. -emin
\_ what does it mean by "80Mhz of bandwidth for 2.4
GHz signals? and why does microwave oven need to
shield the microwave from escaping while cell phone
uses signal in microwave region "openly"?
\_ Because microwaves in an 'oven' are specifically
tuned to vibrate water, which is in most living
things. But cellphone radiation supposedly is
on frequencies that do not affect living things.
Yeah, right.
\_ Well I'm no microwave expert but I'd say that
your roommate's parrot would heat a lot less quickly
with microwaves leaking out of your microwave
instead of reflecting inside.
\_ it means that you can transmit more signal per channel,
which means that you can use a higher bandwidth
modulation technique which is more robust to noise.
i think emin is actually right, and it has nothing
to do with reflections and transmissions. it's more
likely a bandwidth issue. -ali
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