magnetic field

[Bob Myers]

"Dbowey" <dbowey@aol.com> wrote in message
news:20030729213355.02417.00000935@mb-m21.aol.com...

Bob posted, in part:
I don't think it's "too hard" (been licensed for about 30 years,
and have at one time been quite comfortable at well over
20 WPM), but more and more, I DO have to agree that it's
become irrelevant.

Since when is having fun irrelevant?

Obviously it's not, but I think the context was implied
as "from the perspective of determining who should get
a license."

Bob M.

 

[Bob Myers]

"Dbowey" <dbowey@aol.com> wrote in message
news:20030730131424.03081.00000695@mb-m01.aol.com...

I enjoy QRP cw. Running about a half watt input power on 80M at 2am and
having
a ZL come back is a lifetime thrill.

And don't get me wrong - I ENJOY this sort of thing, too. But
it's about as relevant as a "requirement for admission" into the
amateur community as the ability to repair a teletype machine.
I hardly think that eliminating the CW requirement from the test
would eliminate it as a popular operating mode.

Bob M.

 

[Bob Myers]

"Sir Charles W. Shults III" <aichipREM@OVEcfl.THISrr.com> wrote in message
news:seKVa.2304$K4.74695@twister.tampabay.rr.com...

You know, digital is not restricted to binary. Morse code is most
certainly
digital, as it is based on a two valued logic level system, but it also
includes
a time parameter.

My point had nothing to do with this; I'm just tilting at one of
my favorite windmills, which is the massive level of confusion that
surrounds the terms "digital" and "analog".

Simply being an on/off system doesn't make something "digital" -
for example, consider the action of a switch-mode power supply.
Fundamentally, this would have to be considered an "analog" system
(if we MUST use one of these two terms - my personal preference
is to restrict them to those systems carrying information), as the
"on" time of the switch directly controls (i.e., IS ANALOGOUS
TO) the output voltage level (which is what's being regulated) for
a given load condition.

Morse code is a trinary system, in the most rigorous sense.

Sorry, I don't see that, either, unless you're going to suddenly
start calling any sequential logic system (hey, if it's sequential,
it includes a "time parameter", right?) "trinary".

Bob M.

 

[Bob Myers]

"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0307300445.3a9e58ef@posting.google.com...

I will violently agree that all digital systems are made out of analog
components. But Morse code is undoubtedly digital communications.

I have no idea what "analog components" are. "Analog" refers to
a system in which one parameter (say, voltage) is used to directly
represent variations in (i.e., behaves ANALOGOUSLY TO)
another (say, sound). "Analog" and "digital" both refer to means of
encoding information - components cannot be either "analog" or
"digital", although certainly some circuit designs are more useful in
handling one type of communications over the other.

Bob M.

 

[Little Monster]

On Mon, 28 Jul 2003 22:05:23 +0000, scada wrote:

Some early scanners used SCSI cards connected to the ISA bus.

Yahh. What I've read is that the scanner sees an ISA interface. Maybe I
have misinterpreted this.

Monster
--
Spam will eat itself

 

[Jim Thompson]

On 30 Jul 2003 17:14:24 GMT, dbowey@aol.com (Dbowey) wrote:

Michael posted in part:
"When I was a kid and learned of amateur radio, neither the code test
nor the written exam were an obstacle. They were something I had to
pass in order to be licensed, but they were also a sign of accomplishment."

I totally agree. It was a worthy challenge.

Too many people today want THINGS, such as to be able to have and operate a ham
station, but they do not want to put in the effort. They prefer to whine about
how difficult it is. There is no challenge for them, because in their minds
they have already been defeated.

I enjoy QRP cw. Running about a half watt input power on 80M at 2am and having
a ZL come back is a lifetime thrill.

A previous poster commented on the ability of some hams to "make-do" and get
operational with junk. I think that skill is valuable, and ham radio is the
best place to develop it.

Don

I found "hamming" a useful way to learn how to design... build a lot
of circuits you don't understand, then try to figure out why they
work.

I was fortunate to grow up while my father operated a radio/TV repair
shop. So parts were easy to come by... I even had my own parts
account at the local wholesaler.

Since I've never been much of a "chatty-Cathy" I let my license lapse
(K7ZAE) after I cut my design teeth on building solid state stuff for
2-meters.

I consider the folk who won't learn the code real weenies... after all
these years of dis-use I think I could still pass the test, as long as
it's not too fast ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| Jim-T@analog_innovations.com Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

For proper E-mail replies SWAP "-" and "_"

Get Lolita Out of Debt... Add Three Inches to Your Mortgage!

 

[Sir Charles W. Shults III]

"Bob Myers" <nospamplease@addressinvalid.com> wrote in message
news:3f280f4e$1@usenet01.boi.hp.com...

"Sir Charles W. Shults III" <aichipREM@OVEcfl.THISrr.com> wrote in message
news:seKVa.2304$K4.74695@twister.tampabay.rr.com...
You know, digital is not restricted to binary. Morse code is most
certainly
digital, as it is based on a two valued logic level system, but it also
includes
a time parameter.

My point had nothing to do with this; I'm just tilting at one of
my favorite windmills, which is the massive level of confusion that
surrounds the terms "digital" and "analog".

Okay, let me try to understand why you take exception to me calling Morse a
three state digital system.

Simply being an on/off system doesn't make something "digital" -
for example, consider the action of a switch-mode power supply.
Fundamentally, this would have to be considered an "analog" system
(if we MUST use one of these two terms - my personal preference
is to restrict them to those systems carrying information), as the
"on" time of the switch directly controls (i.e., IS ANALOGOUS
TO) the output voltage level (which is what's being regulated) for
a given load condition.

I agree that being on or off does not make it digital, but when you settle
on a small number of discrete, well defined states, you have then defined the
system as being digital. Any time you disallow a continuous spectrum of values,
you lose the whole concept of the system being analog. This is particularly
true of a system of storing or transmitting information. Computers and serial
communications are notable examples.

Morse code is a trinary system, in the most rigorous sense.

Sorry, I don't see that, either, unless you're going to suddenly
start calling any sequential logic system (hey, if it's sequential,
it includes a "time parameter", right?) "trinary".

Nope. I have pointed out that there are two and only two states in the time
regime.

The heart of the definition of digital is that there are discrete, well
defined states for the system. States that do not fall within the defined
conditions are disallowed or undefined.
Analog systems have free ranging signals and there are typically no preset
or discrete states recognized. They can be of literally any value that the
physical system or space can support.
The pedestrian definition often likens digital to a light switch, and analog
to a light dimmer. The crux of it, though, is that in analog systems, you
cannot "pigeonhole" the values in a small, well defined set of states. In other
words, anything goes.
In most straight serial communications, we have a binary system in that only
two possible states are allowed. Those two states are the logical high and
logical low state. They are represented as two distinct voltage levels in most
schemes. Now, while the world is analog, and any type of signal is permissible,
in order for a particular stream of information to qualify as binary it only
needs to exhibit two unique and easily distinguishable states.
Since we recognize the context and the definition, and no "in between"
states are intentionally sent, we would all pretty much agree that any stream of
data that regularly exhibits two and only two states can be thought of as
binary. It can be voltages, as are commonly used in serial communications, or
it can be currents such as the 20 mA system that Teletypes and other machinery
(including CNC) used. But, it could also be light pulses (like IR remote
controls use) or even squirts of water striking a microswitch- there are no
limits to a binary stream of data. Pretty nearly ANY medium can carry it. You
can use pulses of neutrinos or flashes of red and yellow light. All that
matters is that the system supports two and only two states. Are we in
agreement?
Now, since we could also decide that conditions of "signal" and "no signal"
are valid representations, we could (if we so chose) allow a carrier wave to be
sent or not- and use a "carrier detect" scheme to decode the data. Now we have
a system that sends binary states (carrier detected or not detected) and it can
be used to transmit and receive data just as any other system.
What if we encode that as long or short pulses? Now we have simply
rearranged the system so that the presence of carrier simply tells us that data
is present, and the length of the pulses can carry the actual message. I don't
think I would get any argument that this is not a valid system- I can decide
that a one clock cycle pulse is a zero, and a three clock cycle pulse is a one-
and I can disallow any other state. In other words, loss of carrier means
"nothing is being received", and when I do get carrier, I can say that those
pulses of carrier are zeros or ones based on their length.
There is precedent for this in humble serial communications, like RS-232. A
disconnected wire is free floating and can be recognized by some systems as
"hey, the wire is not hooked up!" All it takes is a resistor at the receiving
end that pulls the signal input to a midway state- "illegal". Then, when a wire
is in fact connected, you get only one or zero level signals.
Now, to merge the two systems. We use a time period as defining a one and a
zero, and we use a presence or absence of carrier to tell us when message data
is coming in. Since the state of "carrier on for one pulse" is a zero, and
"carrier on for three pulses" is a one, and "no carrier" is effectively a space,
we have a three state system. It carries a variable length word of data,
anywhere from one to five bits in length, and those bits are zeros and ones.
While there are actually four states, two of them are degenerate and cannot
be readily distinguished- a long "no carrier" state and a short "no carrier"
state will elicit the same response from the system. We end up with three
distinct conditions that the system recognizes, and that is all that is needed
to define it as being trinary.
I hope this makes my opinion (and the supporting evidence) clear.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

[Dbowey]

Bob posted, in part:
<< "Harry Conover" <hhc314@yahoo.com> wrote in message
news:7ce4e226.0307300733.788d7d9d@posting.google.com...

Bob, one argument in support for the continuing requirement for code
proficiency in amateur radio licensing stems from the presumed public
value of amateur radio in times of emergency.

You're right that amateur radio as a whole has been justified,
for years, on the grounds of its usefulness as an emergency
service, and there are countless examples of hams stepping in
and filling the gaps left in commercial or government
communications in natural disasters and so forth. >>
---------------------
I believe the ARRL planted that seed so long ago that it is "general knowledge"
that the primary justification of ham radio is emergency communications. But
THAT IS NOT CORRECT. What the FCC says is:

"Amateur Service. A radiocommunication service for the purpose of
self-training, intercommunication and technical investigations carried out by
amateurs, that is, by duly authorized persons interested in radio
technique solely with a personal aim and without pecuniary interest."

Regardless of how important it has become, there is no mention of providing
emergency services in that FCC definition.

Don

 

[Bob Myers]

"Sir Charles W. Shults III" <aichipREM@OVEcfl.THISrr.com> wrote in message
news:WkVVa.2052$qg3.135589@twister.tampabay.rr.com...

I agree that being on or off does not make it digital, but when you
settle
on a small number of discrete, well defined states, you have then defined
the
system as being digital. Any time you disallow a continuous spectrum of
values,
you lose the whole concept of the system being analog. This is
particularly
true of a system of storing or transmitting information. Computers and
serial
communications are notable examples.

Strictly speaking, that's not true either. It is certainly possible
to conceive of a purely analog system in which the transmission
involves only a small number of discrete possible values. An
analog video interface in which the video source can only do,
say, eight levels of gray is one such example. In short, while most
analog systems ARE capable of continuous variation between
values, there's no real requirement that this must be so. It's
hard to imagine a real need that would drive such a "quantized
analog" scheme, but it surely could be implemented.

The heart of the definition of digital is that there are discrete,
well
defined states for the system.

Actually, the heart of the definition of "digital" lies just where
you might expect to find in - in just what that root word "digits"
means. A "digital" system is one in which information is encoded
as what (for lack of a better term) might be viewed as "numeric"
values Ii.e., "digits") directly, as opposed to being represented in
"analogous" form by some other quantity (e.g., the "voltage for
sound pressure" example I gave earlier).

My favorite example, which I've often used in classes on this
topic, is as follows:

Suppose you're supposed to record the temperature at a
certain location at various times during the day. You might do
this in either of two ways. First, you could get yourself a
piece of graph paper, and every time you take a temperature
reading, make a point on the graph and draw in the next line
segment to connect it to all the previous points. Or you might
simply write down your readings in the form of a table:

12 noon: 72 degrees
1 PM: 73 degrees
2 PM: 75 degrees

and so forth.

The graph paper is an "analog representation" in this model -
the line varies just like the temperature did, to within the limits
of how often and how accurately you took your readings (and
could draw the line!). The table is a "digital" representation -
information stored as symbols that represent numbers directly,
but which have no real quality that varies in a manner akin to the
original parameter.

Bob M.

 

[Dbowey]

Chip posted, in part:
<< Now, to merge the two systems. We use a time period as defining a one and a
zero, and we use a presence or absence of carrier to tell us when message data
is coming in. Since the state of "carrier on for one pulse" is a zero, and
"carrier on for three pulses" is a one, and "no carrier" is effectively a
space,
we have a three state system. It carries a variable length word of data,
anywhere from one to five bits in length, and those bits are zeros and ones.
While there are actually four states, two of them are degenerate and cannot
be readily distinguished- a long "no carrier" state and a short "no carrier"
state will elicit the same response from the system. We end up with three
distinct conditions that the system recognizes, and that is all that is needed
to define it as being trinary.
I hope this makes my opinion (and the supporting evidence) clear.>>
--------------------
Not for me. Everything down to this quoted info was excellent. But I view the
signal as digital for the following.......

Well sent CW is a conbination of dots, dashes, and a couple types of spaces.
The dot period is the standard from which the dashes, and the couple types of
spaces are constructed. I don't recall off-hand the numbers, but this is
close enough for discussion:

dot = 1 unit interval (1 bit)
dash = carrier on for 3 dot intervals.
space between letters = carrier off for 4 dot unit intervals
space between words = carrier off for 7 dot unit intervals

nothing is sent that is not a construct of THE dot unit interval, aka one bit.

The code is sent using a non-return-to-zero (NRZ) code.

Clock is recovered by the mind by simply hearing the signal and syncing up with
the overall rhythm

It sounds and looks binary to me.

Don

 

[Sir Charles W. Shults III]

"Bob Myers" <nospamplease@addressinvalid.com> wrote in message
news:3f284e4d$1@usenet01.boi.hp.com...

"Sir Charles W. Shults III" <aichipREM@OVEcfl.THISrr.com> wrote in message
news:WkVVa.2052$qg3.135589@twister.tampabay.rr.com...


I agree that being on or off does not make it digital, but when you
settle
on a small number of discrete, well defined states, you have then defined
the
system as being digital. Any time you disallow a continuous spectrum of
values,
you lose the whole concept of the system being analog. This is
particularly
true of a system of storing or transmitting information. Computers and
serial
communications are notable examples.

Strictly speaking, that's not true either. It is certainly possible
to conceive of a purely analog system in which the transmission
involves only a small number of discrete possible values. An
analog video interface in which the video source can only do,
say, eight levels of gray is one such example. In short, while most
analog systems ARE capable of continuous variation between
values, there's no real requirement that this must be so. It's
hard to imagine a real need that would drive such a "quantized
analog" scheme, but it surely could be implemented.

I agree with this also. I have seen systems that did use analog channels to
carry specific signal levels.

The heart of the definition of digital is that there are discrete,
well
defined states for the system.

Actually, the heart of the definition of "digital" lies just where
you might expect to find in - in just what that root word "digits"
means. A "digital" system is one in which information is encoded
as what (for lack of a better term) might be viewed as "numeric"
values Ii.e., "digits") directly, as opposed to being represented in
"analogous" form by some other quantity (e.g., the "voltage for
sound pressure" example I gave earlier).

Yes, and digits are exact and discrete representations. And if I make any
electronic system, I can show that it is all analog, but by convention (and
clever design), we can label a small number of well defined states, and make
sure the hardware cannot (under normal circumstances) produce anything other
than those states.
We agree on the convention that (for example) in TTL logic, anything below
0.6 volts is a zero and anything above 2.4 volts is a one. If we measure the
actual voltages present, we are likely to see just about anything from 2.4 to 5
volts present on an output when a logical one is produced. Depends on the exact
logic family and the loading, but we agree on those boundaries.
Likewise, we also see anything from 0.6 volts down to 0 volts as a logical
zero. We have assigned the digits ourselves, and we accept that the hardware is
digital because it is designed not to dally about at some halfway state. Of
course, we have also built specific "guard bands" into the levels to be certain
that no such signal is made. A 1.5 volt level is likely to be interpreted as
anything if applied as an input, but it will not be produced by the system
unless something is broken.
Now, if we built logic that uses a four valued system, we would set four
well defined intervals, along with "guard bands" to isolate them and be certain
that they will not be confused with each other. Three little voltage windows
will be "no man's land" here, and our four logic states would likely be 0, 1/3
of supply, 2/3 of supply, and the supply.
Making it monotonic like this helps us to decide what an errant signal
should be interpreted as- and the key is interpretation.
If I were presented with a signal that showed only 5 discrete signal levels
or values throughout, I would have no problem in accepting that as being a
digital representation. If I can reproduce it with a small handful of states,
and each is clearly unique, then it exhibits "digital-ness".
If, however, it shows stretches of continuous value, then it is an analog
signal that happens to have stretches of digital type data. We know that
television is analog, but nothing prevents us from using that timing and framing
to encode and store digital data. In fact, it has been done. Somebody made
data backup recorders from VCRs a few years back. You could store the data as
video frames.
Here they were clearly storing digital data in an analog medium. But so
does any of the old audio frequency modems.

My favorite example, which I've often used in classes on this
topic, is as follows:

Suppose you're supposed to record the temperature at a
certain location at various times during the day. You might do
this in either of two ways. First, you could get yourself a
piece of graph paper, and every time you take a temperature
reading, make a point on the graph and draw in the next line
segment to connect it to all the previous points. Or you might
simply write down your readings in the form of a table:

12 noon: 72 degrees
1 PM: 73 degrees
2 PM: 75 degrees

and so forth.

The graph paper is an "analog representation" in this model -
the line varies just like the temperature did, to within the limits
of how often and how accurately you took your readings (and
could draw the line!). The table is a "digital" representation -
information stored as symbols that represent numbers directly,
but which have no real quality that varies in a manner akin to the
original parameter.

Once again, I agree with you.
Now, at the point where you decide what the closest integer value to your
reading is, you have quantized your data. Yes, the graph paper is an analog
representation, and yes, the table is digital. Each has a completely different
"flavor" to it.
But nothing (other than the problem with noise creeping into the system)
prevents us from using a 100 valued system. And there are those ISD audio
storage and platback chips which actually break the audio into one of 256
discrete levels and save it in a flash chip of sorts. These pretty much
straddle the border between analog and digital because they have enough
resolution that they are right at the noise limit for what you can tell apart in
terms of "byte" value for each sample.
They are designed to be digital in some respects, but clever work has made
them store roughly sampled audio. I suppose the best way to put this whole
thing is that we label those systems by convention, and we use the criterion of
"ability to represent the contents in a small number of discrete states".
As an aside, I find no problem with requiring Morse to be known to get a
license. We can't reasonably claim it is too difficult- look at all the
programmers who know most of the ASCII code table. And my kids can each
remember about a hundred Pokemon cards with no problem- the difficulty argument
is a hollow one.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

[Sir Charles W. Shults III]

"Dbowey" <dbowey@aol.com> wrote in message
news:20030730185142.00649.00000647@mb-m25.aol.com...

Chip posted, in part:
Now, to merge the two systems. We use a time period as defining a one and
a
zero, and we use a presence or absence of carrier to tell us when message data
is coming in. Since the state of "carrier on for one pulse" is a zero, and
"carrier on for three pulses" is a one, and "no carrier" is effectively a
space,
we have a three state system. It carries a variable length word of data,
anywhere from one to five bits in length, and those bits are zeros and ones.
While there are actually four states, two of them are degenerate and
cannot
be readily distinguished- a long "no carrier" state and a short "no carrier"
state will elicit the same response from the system. We end up with three
distinct conditions that the system recognizes, and that is all that is needed
to define it as being trinary.
I hope this makes my opinion (and the supporting evidence) clear.
--------------------
Not for me. Everything down to this quoted info was excellent. But I view
the
signal as digital for the following.......

But I never claimed otherwise- I clearly said it was a digital system. Just
keep in mind that digital is not the exclusive property of "binary". ANY system
that defines a set of discrete levels and disallows all else is digital,
because, by definition, it can be represented using nothing more than digits.
You can have any number of logic levels in a digital system- 2, 3, 5, 9...
as long as the individual states cannot be confused with each other, your system
is still useful. We limited ourselves to binary just because the logic was easy
to make. It has often been suggested that trinary would be somewhat more
friendly because the three states can carry more information in a given
representation. But practical design and use of trinary computers is still a
problem, and conventions rule.

<snip rest>

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

[Dbowey]

Chip posted in part:
<< It has often been suggested that trinary would be somewhat more
friendly because the three states can carry more information in a given
representation. >>
---------------
Very true. Look at the line code for many DSLs (and basic rate ISDN). They
use quaternary coding to pass more info in less bandwidth.

Don

 

[R. Steve Walz]

Harry Conover wrote:

While not wishing to sound like a "survivalist krank", I do believe
that the aftermath of a nuclear attack is once again surfacing as a
disaster mode that the amateur radio service must be prepared to deal
with. In this connection it must be realized that nearly all of the
solid state based ham gear in use today is not radiation hardened or
protected, hence would be useless in regions nearby such an attack.
-----------

Erroneous. In that case, anyone near it wouldn't either, so there
wouldn't be enough qualified personnel to operate it either, so it
evens out. The EMP mythology is a lie which is *FAR* too widely
propagated. Anywhere EMP would render equipment unusable, it would
also kill the personnel and destroy everything else close at hand
as well by blast. Those very levels of energy density go together
intimately! No such thing occurs as seen in cheap sci-fi movies
where magically everything solid state becomes unusable.

-Steve
--
-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public

 

[Fred Abse]

On Wed, 30 Jul 2003 23:24:31 +0100, Dbowey wrote:

and technical investigations carried out by amateurs

That bit seems to have largely been forgotten by today's "black box"
operators, whose interest seems solely to lie in operating equipment
that they have never even taken the covers off.

Radio is a branch of electrical engineering, which is a branch of applied
physics.


--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Michael Black]

Fred Abse (excretatauris@cerebrumconfus.it) writes:

On Wed, 30 Jul 2003 23:24:31 +0100, Dbowey wrote:

and technical investigations carried out by amateurs

That bit seems to have largely been forgotten by today's "black box"
operators, whose interest seems solely to lie in operating equipment
that they have never even taken the covers off.

Radio is a branch of electrical engineering, which is a branch of applied
physics.

It's suffering from runaway feedback.

Things changed so you could buy increasingly fancy equipment, which
in turn made it easier for people not interested in technical matters
to get into the hobby, which gave enough people to want simpler
entry requirements, which reinforced the number of non-technical people
in the hobby.

Let's make the test simpler --> let's have licenses that don't require
a code test --> let's drop the code test completely.

And after a certain point, the next "logical" step after this
is a desire to drop the technical test completely.

On one hand, people are lamenting that amateur radio (and other
technical hobbies) can't compete in a world of cellphones, internet,
and video games. Yet, too many think the solution is to try to compete,
ie promote amateur radio as a communcations utility, when in reality
it isn't nearly as reliable for that as any of the common devices
available.

Promote it as in the old days, and maybe you won't get so many
newcomers, but you will get a better quality of newcomer.

Mind you, I don't think amateur radio does a good job of promoting
it. Too much effort has gone into reducing the entry requirements,
and not enough of being visible so the kid who is interested in
technical things will find it.

I'm not sure if it's perception or not, but it seems like the local
astronomy clubs here are making an effort to promote their events
beyond those already in the know. Public telescope parties were
an annual thing when I was a kid, but up until, there was a long
period when I was never seeing anything about this.

Michael

 

[Dbowey]

Fred posted:
<< On Wed, 30 Jul 2003 23:24:31 +0100, Dbowey wrote:

and technical investigations carried out by amateurs

That bit seems to have largely been forgotten by today's "black box"
operators, whose interest seems solely to lie in operating equipment
that they have never even taken the covers off. >>
-----------
But let's not let the FCC and ARRL know that. I believe that they believe that
as long as they have Advanced, Amateur Extra, and other "grades" of license
beyond General, all is well with the world.

Don

 

[CWatters]

"Patrick Leonard" <transactoid@rogers.com> wrote in message news:A1nWa.35488

3) If touch the plasma ball and a grounded source, I get shocked (not the
static kind, the current kind).

Well you shouldn't get a shock. I assume we are talking about a decorative
plasma lamp designed for use in the home? (eg not some home made ball
lightening experiment!) Perhaps you should contact the trading standards
association because this sounds like a product recall issue?

 

[Jean-Michel Friedt]

I like to think I'm reasonably knowledgeable in electronic basics....I'll be
going into 2nd year electrical engineering this year. I've never taken any
antenna courses. Anyway, I've always been the sort of person who likes to
play around with electronics and see what's going on for myself. So
recently, I've taken to experimenting with E fields and antennas.

If I am to believe
http://www.epanorama.net/documents/misc/plasmaball.html,
the AC field is at ~25 kHz, meaning you will need a VLF (read,
large/long)
antenna for decent efficiency. Otherwise I believe loop antennas should
be
the most efficient alternative when the size of the antenna is much
smaller
than the wavelength (in the case of the loop, you will be using the H
field
instead of E).

5) In my thread "Can I light an LED with just an antenna" a poster said to
hook the LED across the antenna. I tried this but it never worked. The

because the impedance of the LED is far too low compared to that of the
antenna ?

Jean-Michel

 

[Robert Monsen]

How far is the plate from the sensor? Another option would be to use a Sharp
IR sensor, which you can get for about $10 US. They are quite accurate to
about 3m, and can output distance either as a voltage or as a bit stream.

As far as ultrasonic sensors go, take a look at http://www.digikey.com for
parts. They all seem out of your price range, though.

I managed to obtain some ultrasonic transducers from http://www.allcorp.com
They were cheap, but you'll have to build up a circuit around them to do the
distance measurement. There are various circuits for this published on the
web.

Regards

"Cliff" <nospam@nospam.com> wrote in message
news:%fAWa.43571$o%2.21604@sccrnsc02...

I would like to measure the movement of a 4x4 inch steel plate as it moves
towards and away from an ultrasonic sensor.

The basic idea is to have the ultrasonic sensor pointing directly to the
flat 4x4 inch steel plate. The plate would be moving around 2 feet towards
and away from the sensor.

I don't care about the accuracy of the device; all I care is about the
repeatability of the reading.

I would appreciate if someone could give me a link to such device, I would
be needing around 60 of them so a cheap sensor would be best (under $25 US
dollars if possible)

I appreciate your help.