On 11/1/2014 7:44 PM, wrote:
rickman wrote:
On 11/1/2014 6:20 PM, wrote:
gareth wrote:
"Brian Reay" wrote in message
...
He is confusing the current and voltage distribution plots for waves.

No, there is no confusion on my part. Please explain why you think
that, for I fear that there may be confusion on your part.

Plus,
an RF wave has a magnetic component.

Well, i think we all knew that.


That can't exist IN the antenna
element as it is conductor.

Yes, and no, for it is the magnetic componentry in the wire
that causes the skin effect.

Magnetic fields can exist in a conductor.

Electromagnetic fields can not exist in a conductor.

Now I'm very confused. How can an EM field not exist in a conductor?
Isn't it the E part that creates a gradient which propels the electrons?

Actually it is both.

As long as the antenna is made of linear material, transmit and receive
are reciprocal properties.

The only antennas I can think of that use non-linear materials is some
microwave antennas that include ferrites.

In a perfect conductor, I thought it was the M part that can't exist
inside the conductor. That is one of the causes of the loss of
superconductivity, penetration by an M field. Or do I have this mixed up?

A bit.

Thanks for clearing it up for me.

--

Rick

On 11/1/2014 7:59 PM, wrote:
rickman wrote:
On 11/1/2014 5:31 PM, wrote:
rickman wrote:
On 11/1/2014 1:03 PM, wrote:
gareth wrote:
Ignoring, for the moment, travelling wave antenna, and restricting
discussion to standing wave antennae ...

An antenna is an antenna.

Deep thoughts...


A wave is launched, and radiates SOME of the power, and suffers
both I2R losses and dielectric and permeability losses associated
with creating and collapsing the near field.

Nope, voltage is applied to an antenna causing currents to be created
which in turn cause an electromagnetic field to be created.

As antennas are made of real materials they have a resistance and the
current through that resistance leads to losses.

I thought there were *real* materials with no resistance. Isn't that
what a superconductor is?

Well, to be pendatic, there are no real materials with zero resistance
that can be used to build antennas.

Why can't you build an antenna with a superconductor?


As all the current existing superconductors require a bunch of supporting
equipment to keep them cold, they can't be used for antennas.

Really? What is the problem? There are super conductors at liquid
nitrogen temperatures and you can have that sitting in a flask on your
desk. Why couldn't that cool an antenna? Once you remove the I*R
losses, you don't even have to worry about the radiated power heating
the N2.

If one were realy determined to do it, one could build the antenna
in a non-metalic container of some sort and keep the container filled
with LN2.

I think you are confusing need with practicality. There is nothing to
stop you from making a superconducting antenna. There just isn't a need
for it unless you live in Gareth's world. Hmmm... wasn't that a movie?
Gareth's World?

It is not need versus practicality, it is practicality period.

If room temperature superconductors are ever invented...

However, those are like a cure for the common cold, practical fusion
power, and peace in the Middle East, all just around the corner for
the past half century or so.

I've never heard anyone say either a cure for the common cold or fusion
was "around" the corner. I've never heard anyone say at all that peace
is expected in the middle east.

You must not be very old then...

No, I'm not, I'm much less than a century old.


I believe there are rather cold temperatures in space. A
superconducting antenna could be used there with *no* supporting
"apparatus".

You mean other than the shade screen?

You do understand two big problems with space stuff is how to get rid of
any generated heat and Solar heating?

Is there a lot of solar heating near Jupiter? I didn't realize...



In any case, why?

I^2R losses only become significant in very small antennas and there is
all the space you could ask for in space to build an antenna.

You snipped the part of my post that addressed your questions. It would
be better if you read posts before trimming them.

--

Rick

On 11/1/2014 8:18 PM, wrote:
Wayne wrote:

snip

I was going to point out to Gareth that he is describing behavior in an
antenna system, not an antenna.

I doubt he will EVER understand the difference.

But, I'm done now. No more.

It does become tiresome correcting the same nonsense over and over again.

Then there is no need at all to reply, no?

--

Rick

rickman wrote:
On 11/1/2014 7:59 PM, wrote:
rickman wrote:
On 11/1/2014 5:31 PM, wrote:
rickman wrote:
On 11/1/2014 1:03 PM, wrote:
gareth wrote:
Ignoring, for the moment, travelling wave antenna, and restricting
discussion to standing wave antennae ...

An antenna is an antenna.

Deep thoughts...


A wave is launched, and radiates SOME of the power, and suffers
both I2R losses and dielectric and permeability losses associated
with creating and collapsing the near field.

Nope, voltage is applied to an antenna causing currents to be created
which in turn cause an electromagnetic field to be created.

As antennas are made of real materials they have a resistance and the
current through that resistance leads to losses.

I thought there were *real* materials with no resistance. Isn't that
what a superconductor is?

Well, to be pendatic, there are no real materials with zero resistance
that can be used to build antennas.

Why can't you build an antenna with a superconductor?


As all the current existing superconductors require a bunch of supporting
equipment to keep them cold, they can't be used for antennas.

Really? What is the problem? There are super conductors at liquid
nitrogen temperatures and you can have that sitting in a flask on your
desk. Why couldn't that cool an antenna? Once you remove the I*R
losses, you don't even have to worry about the radiated power heating
the N2.

If one were realy determined to do it, one could build the antenna
in a non-metalic container of some sort and keep the container filled
with LN2.

I think you are confusing need with practicality. There is nothing to
stop you from making a superconducting antenna. There just isn't a need
for it unless you live in Gareth's world. Hmmm... wasn't that a movie?
Gareth's World?

It is not need versus practicality, it is practicality period.

If room temperature superconductors are ever invented...

However, those are like a cure for the common cold, practical fusion
power, and peace in the Middle East, all just around the corner for
the past half century or so.

I've never heard anyone say either a cure for the common cold or fusion
was "around" the corner. I've never heard anyone say at all that peace
is expected in the middle east.

You must not be very old then...

No, I'm not, I'm much less than a century old.

And I'm the better part of one and heard all of those many times now.

I forgot to add true artificial intelligence to the list.

I believe there are rather cold temperatures in space. A
superconducting antenna could be used there with *no* supporting
"apparatus".

You mean other than the shade screen?

You do understand two big problems with space stuff is how to get rid of
any generated heat and Solar heating?

Is there a lot of solar heating near Jupiter? I didn't realize...

Not a lot but the point is cooling options in space are limited and
you said nothing about where in space.

In any case, why?

I^2R losses only become significant in very small antennas and there is
all the space you could ask for in space to build an antenna.

You snipped the part of my post that addressed your questions. It would
be better if you read posts before trimming them.

I snipped nothing when I responded.



--
Jim Pennino

Jeff Liebermann wrote:
On Sat, 01 Nov 2014 18:47:32 -0400, rickman wrote:

I think you are confusing need with practicality. There is nothing to
stop you from making a superconducting antenna. There just isn't a need
for it unless you live in Gareth's world. Hmmm... wasn't that a movie?
Gareth's World?
(...)
I believe there are rather cold temperatures in space. A
superconducting antenna could be used there with *no* supporting
"apparatus".

You don't need to go to outer space to see cryogenic radios in
operation.

You can see space a lot better with a cryogenic radio.


--
Jim Pennino

rickman wrote:
On 11/1/2014 8:18 PM, wrote:
Wayne wrote:

snip

I was going to point out to Gareth that he is describing behavior in an
antenna system, not an antenna.

I doubt he will EVER understand the difference.

But, I'm done now. No more.

It does become tiresome correcting the same nonsense over and over again.

Then there is no need at all to reply, no?

Other than to prevent a casual reader from thinking his nonsense is
reality, not really.

Well, that and I really have a thing about deflating long winded gas
bags.

--
Jim Pennino

On 11/2/2014 1:24 AM, wrote:
rickman wrote:
On 11/1/2014 7:59 PM, wrote:
rickman wrote:
On 11/1/2014 5:31 PM, wrote:
rickman wrote:
On 11/1/2014 1:03 PM, wrote:
gareth wrote:
Ignoring, for the moment, travelling wave antenna, and restricting
discussion to standing wave antennae ...

An antenna is an antenna.

Deep thoughts...


A wave is launched, and radiates SOME of the power, and suffers
both I2R losses and dielectric and permeability losses associated
with creating and collapsing the near field.

Nope, voltage is applied to an antenna causing currents to be created
which in turn cause an electromagnetic field to be created.

As antennas are made of real materials they have a resistance and the
current through that resistance leads to losses.

I thought there were *real* materials with no resistance. Isn't that
what a superconductor is?

Well, to be pendatic, there are no real materials with zero resistance
that can be used to build antennas.

Why can't you build an antenna with a superconductor?


As all the current existing superconductors require a bunch of supporting
equipment to keep them cold, they can't be used for antennas.

Really? What is the problem? There are super conductors at liquid
nitrogen temperatures and you can have that sitting in a flask on your
desk. Why couldn't that cool an antenna? Once you remove the I*R
losses, you don't even have to worry about the radiated power heating
the N2.

If one were realy determined to do it, one could build the antenna
in a non-metalic container of some sort and keep the container filled
with LN2.

I think you are confusing need with practicality. There is nothing to
stop you from making a superconducting antenna. There just isn't a need
for it unless you live in Gareth's world. Hmmm... wasn't that a movie?
Gareth's World?

It is not need versus practicality, it is practicality period.

If room temperature superconductors are ever invented...

However, those are like a cure for the common cold, practical fusion
power, and peace in the Middle East, all just around the corner for
the past half century or so.

I've never heard anyone say either a cure for the common cold or fusion
was "around" the corner. I've never heard anyone say at all that peace
is expected in the middle east.

You must not be very old then...

No, I'm not, I'm much less than a century old.

And I'm the better part of one and heard all of those many times now.

I forgot to add true artificial intelligence to the list.

I believe there are rather cold temperatures in space. A
superconducting antenna could be used there with *no* supporting
"apparatus".

You mean other than the shade screen?

You do understand two big problems with space stuff is how to get rid of
any generated heat and Solar heating?

Is there a lot of solar heating near Jupiter? I didn't realize...

Not a lot but the point is cooling options in space are limited and
you said nothing about where in space.

lol. No, cooling in space is very easy. Heat radiates quite well.
That's why they can power the electronics with RTGs so well.


In any case, why?

I^2R losses only become significant in very small antennas and there is
all the space you could ask for in space to build an antenna.

You snipped the part of my post that addressed your questions. It would
be better if you read posts before trimming them.

I snipped nothing when I responded.

You are right, it is all there.

--

Rick

rickman wrote in :

What? For a wave to have a "bulge" above the top of the tank means
there is a trough well below the top of the tank. The amount of liquid
does not change because you make waves in the tank.


I didn't say it did. Anyway, I've been looking at images on Google,
apparently the single half-wave form is concave in a tank of liquid, not
convex. Maybe that too is possible, I don't know. If it is, then you can add
liquid to what was a brim-fill tank before it overflows once the wave is set
up, which would indicate that a form of storage has been set up.

Look at it another way... Any standing wave shape in a tank will not be flat,
and when the small amount of energy maintaining it is stopped, it will give
back energy until it is flat, so it looks like a way to store energy. A 'tank
ciruit' has to have a way to store energy too.

(As to why I go into these apparently off-topic variations, it's because I
think a person can know something by being very specific, but probably cannot
understand it unless they look at as many other things as possible in which
similar action occurs.)

Jeff Liebermann wrote in
news
Not quite. If you apply energy to a resonant circuit (electrical or
mechanical), that then remove the input, you'll get a damped wave
(i.e. exponential decay) output where the rate of decay is determined
by the losses in the system. You could build a transmission line
oscillator, which would exhibit some rather small damped wave output
when turned off, but in most cases, there's no connection with
reflected or standing waves because there is usually no transmission
line.


Well, doesn't that still mean there's energy there to power that decay? I get
the exponential bit (had to explore that a lot to code a synth. so the
energy never entirely vanishes, sort of like half-life in fissile materials.

Point taken about usually no transmission line. I remember CB'ers talking of
SWR meters and aiming for as little standing wave as possible. That seems to
go with what Jim (Pennino) said about not having a standing wave without a
transmission line.

Might as well be part of the problem. What I do in my spare time. I
recorded these in about 1998. Please forgive my screwups, plagerism,
lack of coherent style, sloppy fingering, etc:
http://802.11junk.com/jeffl/music/


Nice. Though you do what I tend to do, caught in a singular sort of chord
sequence, expression, whatever it is. I got it from listening to Tangerine
Dream. It's a nice trap (and yours is more elegant than mine too) but it is a
trap. I found a way out of it though, if I can make the effort and maintain
the habit... When walking, I hum, or whistle, and the tunage is far more
varied than when I'm in front of an instrument. I have a small USB memoery
thinger with audio recording (and annoyingly short battery life) that I
usually fail to carry with me. Shame, because a couple of days ago I
improvised for about a half hour on a Cuban tune, 'Chan Chan', very
effectively, and had never done that before. The more I learn about Beethoven
and Schubert, the more I hear about how good they were at improvisation! Most
people seem to think that 'vclassical' was all ablout written formalism. Of
course it wasn't... it was closer to jazz in the sense that it was about
capturing improvisation. Their skill was in doing exactly that. Mozart heard
Allegri's 'Misereri' at one sitting, and recalled enough to write it down
later. I can't do that, but with a bit of technical help (if I can be
bothered to persist in using it), I might make a few things, at least enough
to test the instrument I'm trying to byuild. I have no web storage, but if
you're interested I can try to put three of four bits into a Usenet test
binary group somewhere.. They're not very elaborate, just a few very varied
ideas.

rickman wrote in :

I believe there are rather cold temperatures in space. A
superconducting antenna could be used there with *no* supporting
"apparatus".


There's still such a thing as radiation resistance, I think, so it wouldn't
stay cold even there. Given the size of a body, there's a limit to how fast
it can get rid of heat at a given temperature.. I don't know the proper
terminology for it though. Anyway, at low tenperature, the rate it can
radiate heat is low, so it will quickly warm up out of low-temp
superconducting state.