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PICList Thread
'[EE]5 kHz wireless'
2004\11\26@032441 by Per Linne

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face
A potentional client has approached me. They are in the
physiological niche. They want me to develop a thing to
some equipment they have. I understand that it has to do
with some kind of (human) pulse measurement device. They say
that this equipment communicates wirelessly over 5 kHz!!??
With the risk of making a fool of myself (which I do now and then),
I ask: I there really such a thing? (5 kHz wireless,  that is.)
I have never seen anything about such a low frequency. Must
be vveerryy long waves!!?? Or have they (or I) misinterpreted
the devices data?

Regards,
Per Linne

____________________________________________

2004\11\26@041606 by Russell McMahon

face
flavicon
face
>A potentional client has approached me. They are in the
> physiological niche. They want me to develop a thing to
> some equipment they have. I understand that it has to do
> with some kind of (human) pulse measurement device. They say
> that this equipment communicates wirelessly over 5 kHz!!??
> With the risk of making a fool of myself (which I do now and then),
> I ask: I there really such a thing? (5 kHz wireless,  that is.)

This is very probably (ie almost certainly) intended to do much the same job
as the "Polar" heart rate monitors which transmit a burst signal over up to
a few metres at 5 kHz. This is near field communications rather than true
RF. End result is about the same.

For a complete description of a do it your self receiver with circuit and
more see

       http://www.ricksunfinishedstuff.com/hrm/index.html

Transmitter circuits are usually a little rarer as they have to compete with
the Polar circuits which run off the smell of an oily battery for months. As
i recall they typically use a 4069 inverter IC which is triggered into a
burst of oscillation by the heart signal.



       Russell McMahon




____________________________________________

2004\11\26@044611 by Luis.Moreira

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face
Hi Per
It's probably the signal not the carrier.
Regards
       Luis

-----Original Message-----
From: Per Linne [spam_OUTper.linneTakeThisOuTspamswipnet.se]
Sent: 26 November 2004 08:24
To: PICLIST
Subject: [EE]5 kHz wireless

A potentional client has approached me. They are in the
physiological niche. They want me to develop a thing to
some equipment they have. I understand that it has to do
with some kind of (human) pulse measurement device. They say
that this equipment communicates wirelessly over 5 kHz!!??
With the risk of making a fool of myself (which I do now and then),
I ask: I there really such a thing? (5 kHz wireless,  that is.)
I have never seen anything about such a low frequency. Must
be vveerryy long waves!!?? Or have they (or I) misinterpreted
the devices data?

Regards,
Per Linne

____________________________________________

2004\11\26@051055 by Gerhard Fiedler

picon face
> ... which transmit a burst signal over up to  a few metres at 5 kHz. This
> is near field communications rather than true  RF. End result is about
> the same.

Why do you say "rather than /true/ RF"? Aren't both about elecromagnetic
fields, and the difference is just in the reach and other properties
related to the wavelength or frequency? If this is the case, someone also
could say that the UHF and higher ranges aren't really true RF because they
don't go around the globe... :)

Gerhard
____________________________________________

2004\11\26@060127 by andrej.nemec

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face
Russian transmitter ZEVS works (worked ?) on 82 Hz (yes, 82 Hertz), US called
SANGUINE works on 76 Hertz.

So 5kHz (5000 Hz) is almost high frequency...;-)


On 26 Nov 2004 at 9:23, Per Linne wrote:

{Quote hidden}

> ______________________________________________

2004\11\26@062535 by Alan B. Pearce

face picon face
>So 5kHz (5000 Hz) is almost high frequency...;-)

I remember seeing an article many years ago about some guys investigating
low frequency propagation around 1kHz. They arranged a dipole in Antarctica,
which was 21 miles long IIRC.

____________________________________________

2004\11\26@070610 by Russell McMahon

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>> ... which transmit a burst signal over up to  a few metres at 5 kHz. This
>> is near field communications rather than true  RF. End result is about
>> the same.

> Why do you say "rather than /true/ RF"? Aren't both about elecromagnetic
> fields, and the difference is just in the reach and other properties
> related to the wavelength or frequency? If this is the case, someone also
> could say that the UHF and higher ranges aren't really true RF because
> they
> don't go around the globe... :)

"True RF" occurs when the electric and magnetic components settle down to a
fixed ratio and propagation through the medium occurs without anomalous
behaviour or changes of impedance with position. The impedance of free space
is about 377 ohms (120 Pi).
For locations close to the aerial where this is not the case we are said to
be in the "near field".
Here's a brief but useful summary of this far from intuitive subject

       http://whatis.techtarget.com/definition/0,,sid9_gci845268,00.html

Those who do not run screaming and dive under a bed when Maxwell is trotted
out (I often have a very strong inclination to do so) and those who wish to
see how complex something can be that sounds potentially simple if one could
but understand it, may enjoy.

       http://www.hydrino.org/Maxwell/mxsec798.pdf

8 or 9 pages of differential equations.
Answer = 377 ohm :-)

Measurements of antenna performance are normally carried out beyond the near
field. Some antennas have an immense near field - the Jodrell Bank radio
telescope near field extends to beyond the atmosphere, making testing
antenna characteristics "difficult".

Near field energy transfer is predominantly by electric field. There is a
whole new industry growing up around near field short range communication
devices. A useful page on basic concepts

       http://www.conformity.com/0102reflections.html

Nokia introduces NFC (near field communications) in phones for short range
interaction

   http://www.mobileburn.com/news.jsp?Id=939&source=SIDEBAR

When it gets an industry forum you're in trouble :-) (Nokia again)

       http://www.nfc-forum.org/

The mighty Philips gets in on the act

       http://www.semiconductors.philips.com/markets/identification/products/nfc/

They say;    Acting as a secure gateway to the connected world, tomorrow's
NFC-enabled mobile devices will allow consumers to store and access all
kinds of personal data - at home or on the move. Simply by bringing two
NFC-enabled devices close together, they automatically initiate network
communications without requiring the user to configure the setup.
Muscling in one Bluetooth's territory :-)

The market researchers get in on the act

       http://www.abiresearch.com/reports/NFC.html

Super luminal propagation voodoo posing as formal physics (may be true
though ;-) )

   http://arxiv.org/abs/physics/0009023


Google does 495,000 hits on "near field"



      RM



____________________________________________

2004\11\26@092921 by Roy J. Gromlich

picon face
I would guess they mean they need a kHz bandwidth, but
that is just a guess.  A kHz wireless link is certainly
possible, but I suspect that - with a kHz carrier, the data
signal bandwidth would be only 10-20 Hz. There are
certainly physical parameters which change that slowly.

Roy
{Original Message removed}

2004\11\26@120140 by Peter L. Peres

picon face

On Fri, 26 Nov 2004, Per Linne wrote:

> A potentional client has approached me. They are in the
> physiological niche. They want me to develop a thing to
> some equipment they have. I understand that it has to do
> with some kind of (human) pulse measurement device. They say
> that this equipment communicates wirelessly over 5 kHz!!??
> With the risk of making a fool of myself (which I do now and then),
> I ask: I there really such a thing? (5 kHz wireless,  that is.)
> I have never seen anything about such a low frequency. Must
> be vveerryy long waves!!?? Or have they (or I) misinterpreted
> the devices data?

It works. Just use inductive antennas and it will work.

Peter
____________________________________________

2004\11\26@142301 by madscientist

picon face
and this extremely low frequencies are used to communicate with
submerged submarines as the higher bands simply don't work under water. of course this limits them to various types of code service.  hence in
some movies the long reception time when they receive an "EAM" or other
communication.  it takes a long time to send a few sentences at the very
low data rate required along with error checking and redundancy.  there
are a number of amazingly low frequency services, there are also some in
the 10's of khz range, also very, very long wave.

.....andrej.nemecKILLspamspam@spam@uni-mb.si wrote:
>
> Russian transmitter ZEVS works (worked ?) on 82 Hz (yes, 82 Hertz), US called
> SANGUINE works on 76 Hertz.
>
> So 5kHz (5000 Hz) is almost high frequency...;-)
-------

-- “Cowardice asks the question: is it safe? Expediency asks the question:
is it politic? Vanity asks the question: is it popular? But conscience
asks the question: is it right? And there comes a time when one must
take a position that is neither safe, nor politic, nor popular- but one
must take it simply because it is right.” : Martin Luther King Jr.
1929-1968 <http://www.guardian.co.uk/worldlatest/story/0,1280,-4614717,00.html>

___________________________________________

2004\11\26@142728 by madscientist

picon face
the distinction being that you are closer than a wavelength and a true
EM field isn't relevant, rather it's entirely a magnetic coupling of the
source and receiver with no significant electrical field generated that
close, and by the time you are a wavelength or several away the power
has dropped off to well below background noise, hence no detectable
electro-magnetic field ever forms and you are only detecting a change in
the local magnetic field.  with some of the other services that operate
at high powers of course there is a true electro-magnetic wave formed
within the detection range.  i believe some of these are/were used for
navigational purposes long before gps (i.e. in tube days, when even the
oscillators were tube type).  i've seen pictures of some of the huge,
huge tubes and coils used in the final stages of these monsters, think
very large copper tubing in coils that are bigger than you are!

Gerhard Fiedler wrote:
>
> > ... which transmit a burst signal over up to  a few metres at 5 kHz. This
> > is near field communications rather than true  RF. End result is about
> > the same.
>
> Why do you say "rather than /true/ RF"? Aren't both about elecromagnetic
> fields, and the difference is just in the reach and other properties
------

-- “Cowardice asks the question: is it safe? Expediency asks the question:
is it politic? Vanity asks the question: is it popular? But conscience
asks the question: is it right? And there comes a time when one must
take a position that is neither safe, nor politic, nor popular- but one
must take it simply because it is right.” : Martin Luther King Jr.
1929-1968 <http://www.guardian.co.uk/worldlatest/story/0,1280,-4614717,00.html>

___________________________________________

2004\11\26@170030 by Jinx

face picon face
> Muscling in one Bluetooth's territory :-)

Microchip have App Notes for a LF Magnetic link, something
I have a use for shortly

AN232 (DS00232A) - Low Frequency Magnetic Transmitter Design
AN912 (DS00912A) - Designing LF Talkback For A Magnetic Base Station

Also, I don't recall the pdf number, they have a circuit for using the
PIC's own crystal as the carrier for wireless comms


____________________________________________

2004\11\26@171658 by olin_piclist

face picon face
Per Linne wrote:
> I ask: I there really such a thing? (5 kHz wireless,  that is.)

Yes.  A common example of very low frequency "RF" are those heart rate
monitors you strap around your chest that display on a wrist watch.  I once
had to write PIC code to interpret the pulses from such a heart rate
receiver and produce beats per minute.  It's not as easy as it sounds due to
large amounts of ambient noise.  The algorithm ended up being rather
complicated, but I did manage to get better response time and the same
accuracy as the Polar (or was the Sports Intruments?) watch.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\11\26@172547 by olin_piclist

face picon face
Gerhard Fiedler wrote:
> Why do you say "rather than /true/ RF"?

First, "RF" stands for "radio frequencies".  Not too many radios operate on
5KHz carriers.  However, the real distinction is near field versus far
field.  5KHz at a meter or two is definitely near field.  Most "radio" is
intended for transmission over distances of multiple wavelengths.  In that
case, the receiver does not effect the transmitting antennas
characteristics.  The energy is essentially sent and forgotten.  In near
field, the receiver couples back to the transmitter.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\11\27@005209 by Ed Browne

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face
Yes.  There are "cave" radios operating at very low frequencies and I helped
design a system to receive communications from a downhole tool operating at
very low frequencies.  Already mentioned was the submarines, but some little
known applications involve listening to lightning sprites and earthquakes.
IIRC The earthquake theory is that large piezo electric discharges are given
off as a result of the stresses prior to movement.  There are a whole
variety of sprites that give off wild effects and a number of websites that
contain the sounds. Fascinating stuff.

http://www.elfrad.net/index.htm

{Original Message removed}

2004\11\27@060814 by Gerhard Fiedler

picon face
the madscientist wrote:

> the distinction being that you are closer than a wavelength and a true
> EM field isn't relevant, rather it's entirely a magnetic coupling of the
> source and receiver with no significant electrical field generated that
> close,

If I understood it correctly, it seems to be the other way round: the near
field is mostly an electric field?

see http://www.conformity.com/0102reflections.html

Gerhard
____________________________________________

2004\11\27@075132 by Gerhard Fiedler

picon face
Russell McMahon wrote:

>>> ... which transmit a burst signal over up to  a few metres at 5 kHz. This
>>> is near field communications rather than true  RF. End result is about
>>> the same.
>
>> Why do you say "rather than /true/ RF"? Aren't both about elecromagnetic
>> fields, and the difference is just in the reach and other properties
>> related to the wavelength or frequency?
>
> "True RF" occurs when the electric and magnetic components settle down to a
> fixed ratio and propagation through the medium occurs without anomalous
> behaviour or changes of impedance with position.

Thanks for the interesting intro. My doubt was more about what is
considered (or not) "RF", but this got a bit answered through the back door
:)

Is there a clear definition for what RF means (or "true RF")? Olin seems to
indicate a frequency range, Russell says it's transmission of
electromagnetic wave energy in the far field (thus a combination of
frequency and distance).

The thing is, I thought I had an understanding of the term "RF", somewhat
intuitively, but that got shaken up by the expression "true RF" :)  Or am I
chasing a fata morgana, and this all is not really well defined?


> Measurements of antenna performance are normally carried out beyond the near
> field. Some antennas have an immense near field - the Jodrell Bank radio
> telescope near field extends to beyond the atmosphere, making testing
> antenna characteristics "difficult".

This here seems to use a different meaning of "near field", right? A
meaning that is related to the construction of the antenna, rather than the
properties of a field. (Or is this an antenna designed for frequencies
under 2 kHz?)

After reading some more, it seems that "near field" has different meanings
depending on the context. Like here
http://en.wikipedia.org/wiki/Near-field_region , where one of the meanings
is dependent on the construction of the antenna.

One interesting definition of "near field" I found is: "One classical
definition of far-field is where a source behaves as a point-source,
whereas, in the near-field, the source behaves as an extended source."

Gerhard
____________________________________________

2004\11\27@083047 by Russell McMahon

face
flavicon
face
>>> Why do you say "rather than /true/ RF"? Aren't both about elecromagnetic
>>> fields, and the difference is just in the reach and other properties
>>> related to the wavelength or frequency?

>> "True RF" occurs when the electric and magnetic components settle down to
>> a
>> fixed ratio and propagation through the medium occurs without anomalous
>> behaviour or changes of impedance with position.

> Thanks for the interesting intro. My doubt was more about what is
> considered (or not) "RF", but this got a bit answered through the back
> door

> Is there a clear definition for what RF means (or "true RF")? Olin seems
> to
> indicate a frequency range, Russell says it's transmission of
> electromagnetic wave energy in the far field (thus a combination of
> frequency and distance).

I'll stick by my definition. I think it is usefully meaningful in most
cases.
Olin's definition is IMHO one based on typical cases rather than defining
anything. he is right that very little RF is used at 5 kHz but that doesn't
mean 5 kHz can't be RF.

The reason that the antenna gets in on the act and that distance varies with
antenna structure is that the manner in which it generates the field affects
how far away one needs to be before the perturbations aren't felt. A dipole,
dish, or colinear array are going to have different interactions between
driving element, driven elements if any) and this will affect how long/far
it takes for the generation method to appear "seamless".

Whether you are in near field or not is often expressed in terms of the
distance from the antenna BUT this is similar to Olin's definition - it is a
staement of what is usually seen, not a hard and fast law that governs how
far near field extends. The determiner (by definition) of whether you are in
far field is whether the E/H ratio has stabilised at the constant vaklue
which is characteristic of the transmission medium.

In the case of the Jodrell bank antenna the very very large physical size
(and probably the characeristics of the dish itself) are relevant.

Googles ....

Hmmm - can't find anything about the near field range of the  JB dish - I
think I read it in an Electronics Australia magazine some years ago. BIMBW
as always.

> Or am I chasing a fata morgana, and this all is not really well defined?

As above. While "true RF" was my terminilogy, what I was trying to point out
was that the transmission method almost certainly used predominantly
electric field transmission fwiw. You'll note that the various short range
coms devices that i mentioned are working in this mode.



       Russell McMahon


____________________________________________

2004\11\27@164020 by madscientist

picon face


Gerhard Fiedler wrote:
---------
>
> Is there a clear definition for what RF means (or "true RF")? Olin seems to
> indicate a frequency range, Russell says it's transmission of
> electromagnetic wave energy in the far field (thus a combination of
> frequency and distance).
>
> The thing is, I thought I had an understanding of the term "RF", somewhat
> intuitively, but that got shaken up by the expression "true RF" :)  Or am I
> chasing a fata morgana, and this all is not really well defined?

ok, i have no idea what "fata morgana" means.  but "RF" in this case is
a clear example of a technical terms meaning blurring.  originally "RF"
no doubt meant the range of frequencies useful for radio communications,
but over time that range extended in both directions.  indeed at the
high end it is blurring into optical frequencies, or wavelengths (the
more common term, at that end of the spectrum).

> One interesting definition of "near field" I found is: "One classical
> definition of far-field is where a source behaves as a point-source,
> whereas, in the near-field, the source behaves as an extended source."

that is doubtless the most "correct" definition.

i also suspect that some near field systems are electric field based,
and some are magnetic depending on the frequency and the intended range.
you certainly are not going to be able to use an electric field of low
frequency across a room without major filtering problems from the static
discharges that are many decibels more intense than the signal
generator, while at very short distances of inches or less you can
obviously use either.  it depends on the antenna design, i.e. whether it
is designed to produce a magnetic field or an electric field
predominantly.  a coil will produce a magnetic field, a wire connected
at only one end would produce an electric field, in the near field,
right?  in the far field the electromagnetic wave is a consequence of
the magnetic field inducing an electric field which draws energy from
the magnetic field and vice versa in quadrature in space, time, and
orientation, i think (at least for non-circularly polarized waves which
i think get more complicated).  in the far field you can't have one
without the other if the field is changing, in the near field one can be
much stronger than the other and more significant while the other one
necessarily does still exist.

--
Just the truth Corporate controlled news is white washing, the real
motives and aims of heir Bush:
www.informationclearinghouse.info/article6895.htm
<www.guardian.co.uk/print/0,3858,5069215-103677,00.html>
www.informationclearinghouse.info/article7369.htm
www.informationclearinghouse.info/article7370.htm
____________________________________________

2004\11\29@044427 by dr. Imre Bartfai

flavicon
face

Hi,

I have seen a heartbeat transmitter (actually a belt), which transmits on
50kHz.

Imre

On Fri, 26 Nov 2004, Alan B. Pearce wrote:

>> So 5kHz (5000 Hz) is almost high frequency...;-)
>
> I remember seeing an article many years ago about some guys investigating
> low frequency propagation around 1kHz. They arranged a dipole in Antarctica,
> which was 21 miles long IIRC.
>
> ______________________________________________

2004\11\29@155117 by Per Linne

flavicon
face
Friends,

I am overwhelmed by all the very qualified responses I got on my question.
(And a few as confused as me as well.) I also apologize for me slipping on
the K. :-) As with programming, it seems there's always something you miss.

Thank you very much. And as usual the most valuable comments came
from the persons I actually expected. How can you know all these things?...

Pity one of you never got to Sweden while you were in Europe.

One final thing I don't get. I can understand subwater and subground
wireless communication problems, but what is the point in this environment?
I guess I should take the time to read all mr McMahon's suggested links.
Even Nokia (our neighbors here in Sweden) is mentioned.

Grateful regards,

PerL


{Original Message removed}

2004\11\29@185411 by olin_piclist

face picon face
Per Linne wrote:
> One final thing I don't get. I can understand subwater and subground
> wireless communication problems, but what is the point in this
> environment?

Let's say you owned a fleet of nuclear submarines that have the capability
of annihilating your enemy.  Of course you need to send them commands like,
"Nuke Petropavlovsk now", "Oops, never mind", and "time to come home, the
IRS wants to audit your taxes".  The problem is how to send those messages
without the subs getting into danger.  Anytime a sub gets near the surface,
it runs the risk of its position being detected by enemy satellites.  You
might decide to send very low frequency radio messages, and put a very long
antenna in northern Michigan or someplace.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\11\29@212321 by Vitaliy Maksimov

flavicon
face
I think the question was "what is the point of using low frequency in
applications other than subwater and subground"?

Also, if you were to nuke Petropavlovsk-Kamchatsky I think it would make
more sense to put the antenna somewhere in Alaska.  Or do you mean the other
Petropavlovsk (in Kazakhstan)?


{Quote hidden}

> ______________________________________________

2004\11\29@225542 by Edward Gisske

flavicon
face
There are a couple of the aforementioned ELF antennas. One in the Upper
Peninsula of Michigan and another just north of me in Clam Lake Wisconsin.
They are 28 miles long beverage-style wire antennas  put up on low poles.
The reason for the location has more to do with the type of rock underground
than the proximity to the subs. The Clam Lake site was decommissioned
earlier this year. They ran at 78 Hz or so, as I remember.
Ed G.

{Original Message removed}

2004\11\30@025458 by Per Linne

flavicon
face
Yes, excactly. That's why I rerefered to:

>""Polar" heart rate monitors which transmit a burst signal over up to
> a few metres at 5 kHz.

Some difference to the submarine example.

PerL

{Original Message removed}

2004\11\30@042859 by Russell McMahon

face
flavicon
face
> One final thing I don't get. I can understand subwater and subground
> wireless communication problems, but what is the point in this
> environment?

As well as the various answers already given, in the context of short range
communications, some reasons are.

- Not covered by regulatory requirements (yet)(and maybe never).

- Cheap. Chances are the communications is only very broadly tuned with
everyone sharing the channel. Maybe a few channels would be provided.

- Allows short range coms between eg PDA's, cell phone, laptops etc at a far
far lower cost than using eg Bluetooth or 802.11x

- At very low frequency with small poorly defined aerials (the user may be
part of the aerial system) it's almost impossible to do short range coms
that isn't near field so one may as well sell it as a feature :-)


       RM



____________________________________________

2004\11\30@075102 by olin_piclist

face picon face
Vitaliy Maksimov wrote:
> Also, if you were to nuke Petropavlovsk-Kamchatsky I think it would make
> more sense to put the antenna somewhere in Alaska.

I think they had a variety of places in mind, most of them not in
Kamchatsky.  However, with such long wavelengths you can get away with one
location that covers a good portion of the globe.  I'm sure they gave it a
lot of thought before they picked the Michigan upper penninsula.  Hmm, well
then again maybe it had more to do with a porkbarrel project for a
particular senator.  Either way I'm not privy to the reasoning.

> Or do you mean the other Petropavlovsk (in Kazakhstan)?

I didn't know there was one in Kazakhstan.  I'll have to look that one up.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
____________________________________________

2004\11\30@210812 by Vitaliy Maksimov

flavicon
face
Russell wrote:

> As well as the various answers already given, in the context of short
> range communications, some reasons are.
[snip]
> - Allows short range coms between eg PDA's, cell phone, laptops etc at a
> far far lower cost than using eg Bluetooth or 802.11x

This sounds very interesting.  How woud it compare to IrDA in terms of range
and maximum baud rate (~1.0m, 115k)?  Also, wouldn't this system be more
susceptible to noise?

Best regards,

Vitaliy

____________________________________________


'[EE]5 KHz wireless'
2004\12\01@072127 by Gerhard Fiedler
picon face
Vitaliy Maksimov wrote:

>> As well as the various answers already given, in the context of short
>> range communications, some reasons are.
> [snip]
>> - Allows short range coms between eg PDA's, cell phone, laptops etc at a
>> far far lower cost than using eg Bluetooth or 802.11x
>
> This sounds very interesting.  How woud it compare to IrDA in terms of range
> and maximum baud rate (~1.0m, 115k)?  Also, wouldn't this system be more
> susceptible to noise?

What they seem to target are communications up to a few centimeters of
range. This is different from IR, and allows a higher certainty with what
device you are communicating.

>From http://www.nfc-forum.org/aboutnfc/index.html :

"NFC operates in the 13.56 MHz frequency range, over a distance of a few
centimeters. Operating at data rates of 106 kbits/s and 212 kbits/s, NFC is
compatible with Philipsÿ MIFARE® (ISO 14443 A) and Sonyÿs FeliCa smart card
protocols, respectively. However, higher transmission speeds can be
achieved between dedicated NFC devices -- initially up to 424 kbits/s --
with potential for higher bit rates."

Gerhard

___________________________________________

2004\12\01@150614 by Vitaliy Maksimov

flavicon
face
Gerhard,

>From what I understand, Russell was referring to low frequency (5kHz) near-field communication:

> - At very low frequency with small poorly defined aerials (the user may be
> part of the aerial system) it's almost impossible to do short range coms
> that isn't near field so one may as well sell it as a feature :-)

At distances up to a few centimeters, I think you can use simple inductive coupling.

Gerhard Fiedler <listsspamKILLspamconnectionbrazil.com> wrote:

[snip]
{Quote hidden}

___________________________________________


'[EE]5 kHz wireless'
2005\11\03@033153 by Per Linne
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Almost a year later this question comes up again, for a project
in which I am partly involved. In your comment you say:
"...from such a heart rate receiver...". Do you mean that there
already was (is) a receiver that you could add your solution to?
So you didn't have to make the receiver as well?
If I've got you right, where can one get this receiver?

Regards,
PerL

{Original Message removed}

2005\11\03@094626 by olin piclist

face picon face
Per Linne wrote:
> Almost a year later this question comes up again, for a project
> in which I am partly involved. In your comment you say:
> "...from such a heart rate receiver...". Do you mean that there
> already was (is) a receiver that you could add your solution to?
> So you didn't have to make the receiver as well?
> If I've got you right, where can one get this receiver?

I don't know if there are off the shelf receivers for OEMs to integrate into
their equipment.  Talk to Sports Instruments and Polar.  Those were the two
big players 5(?) years ago when I wrote the PIC code to interpret the pulses
for the bike logger.  A custom receiver was designed for that product
although I wasn't the one that did that design.

By the way, this was done for the ancestor of what is now the PowerTap
bicycle ride logger from CycleOps.  The product was sold to different
companies twice I think and I haven't been envolved with it for years.  I
think they are now using TI micros although the earlier versions used PICs.


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consultant in 2004 program year.  http://www.embedinc.com/products

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