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Dental filling radio reception?

D

Danny T

Jan 1, 1970
0
Bob said:
But the real show-stopper, I think, would be the fact that
the whole "radio" is inside the mouth, surrounded by
conductive tissue with no antenna protruding... a pretty
good Faraday cage, I reckon. (Or maybe the radio
only works when you stick out your toungue...!)

And it just so happens that your teeth are "tuned" perfectly to a local
station?
 
A

Anthony Fremont

Jan 1, 1970
0
Danny T said:
And it just so happens that your teeth are "tuned" perfectly to a local
station?

Well that's the really neat thing about AM demodulation, you don't have
to have anything tuned. You only need a simple rectifier.
 
D

Danny T

Jan 1, 1970
0
Anthony said:
Well that's the really neat thing about AM demodulation, you don't have
to have anything tuned. You only need a simple rectifier.

I don't understand - my stereo can tune into different AM stations! :-\
 
A

Anthony Fremont

Jan 1, 1970
0
Danny T said:
I don't understand - my stereo can tune into different AM stations!
:-\

That's because it is employing *selectivity*, in the front-end and in
the IF section(s). The nature of AM broadcast signals make them very
easy to convert directly to audio frequencies. An antenna, a diode, and
a ground connection are all that is needed to demodulate a strong AM
signal. A set of high impedance headphones across the diode will allow
you to listen. Just like this:
http://science.howstuffworks.com/radio9.htm
It's actually a bit more complex in that what really (as in the real
world) constitutes an antenna and a ground can get kind of odd. ;-) If
you want to do more complex things (like actually chose a station), you
will need to use tuned circuits and active semiconductors to improve
selectivity, sensitivity, output volume etc...
 
S

SioL

Jan 1, 1970
0
Danny T said:
I don't understand - my stereo can tune into different AM stations! :-\

Its quite simple, take 10-20m of wire and spread it around, if possible to a tree.
Make a simple detector with a shottky or germanium diode with smoothing cap,
attach sensitive headphones to the output of detector and you've got AM radio.

It will pick up strongest local station, no tuning needed.

SioL
 
D

Danny T

Jan 1, 1970
0
SioL said:
Its quite simple, take 10-20m of wire and spread it around, if possible to a tree.
Make a simple detector with a shottky or germanium diode with smoothing cap,
attach sensitive headphones to the output of detector and you've got AM radio.

It will pick up strongest local station, no tuning needed.

It's true about learning something new every day! I've learnt a lot more
from this group in the last few weeks though - think I'll stick around!! :)
 
B

Bob Masta

Jan 1, 1970
0
And it just so happens that your teeth are "tuned" perfectly to a local
station?

Well, it helps if your teeth look like the pushbuttons on an old
car radio... just bite down on the proper tooth! ;-)



Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
 
D

Dr Engelbert Buxbaum

Jan 1, 1970
0
Bob said:
Hi, everyone.

For years I've heard vague stories about people receiving radio
broadcasts through their dental work. The stories have all the
characteristics of a classic urban legend, and I'm pretty sure
that's exactly what they are.

Hmm, I could imagine the amalgam to act as a crystal detector, like in
the early radios in the 1920's. But what would act as ear phone, and
what as resonance circuit?
 
B

Bob Masta

Jan 1, 1970
0
Hmm, I could imagine the amalgam to act as a crystal detector, like in
the early radios in the 1920's. But what would act as ear phone, and
what as resonance circuit?

As noted in other responses, a resonant circuit is not mandatory,
especially for strong local AM stations. I suspect anyone who has
ever built a simple crystal radio (diode or traditional) in an urban
area has noted that one strong local station seems to dominate the
whole band, regardless of where tuned.

Likewise, there are electromechanical transduction processes that
work on biological tissue. The ones I have experimented with work
at higher voltages (several volts RMS), but that was to produce a
sound that was audible in free air. (This was a signal generator
with a paper clip on the hot lead. If you brushed your fingertip
on the clip in *just* the right way, you could hear the oscillator
frequency. Don't recall how the ground was connected.)

And of course the best example of a bio-electro-mechnical
transducer is an outer hair cell from the inner ear. These
guys have on the order of 100 mV across them, and when
the stereocilia ("hairs") at one end are moved by vibration,
they modulate conductance channels and the cell conducts
current at the vibration frequency. That part of the system
is of course going from mechanical to electrical. But in
response to the changing potential across the cell, it changes
its length and actually ends up boosting the mechanical
input signal. As far as I know, there has been no systematic
survey of other tissues to see if they have this
electrical-to-mechanical transduction property, unrelated
to their normal function.

So *in theory* there could be a transduction system.

My question was related to the signal level that could
be present in the first place, given what I supposed
is the Faraday shielding of the conductive tissue of
the head and mouth. I think there must be a way to
compute this, since the same issue would be involved
in (for example) using conductive foams and coatings
on electronic apparatus to get EMC compliance.

Best regards,





Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
 
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