Richard Clark wrote:
On Thu, 17 Mar 2011 12:52:28 -0700, Jim Lux
wrote:

Certainly he predicts that the temporal dispersion is going to be 0.1ps
for near IR, which is, shall we say, challenging to measure.

Why?


measuring things to tenths of a picosecond, repeatably, can be tricky..
That's like measuring the phase difference between two 10 GHz signals
to 0.3 degrees. Or, another way to look at it is 1 picolightsecond is
about a third of a millimeter.

You're looking at
a) figuring out how to generate two signals at near IR that has a
frequency offset that can be accurately controlled. Probably some sort
of heterodyne mixing scheme would be easiest.
b) sending those two signals over the optical path through
interplanetary space.
c) recovering the signals, measuring the propagation time variation
(say, by looking at the phase difference between the modulation
signals), and then removing atmospheric effects.
d) it's probably going to be a pretty weak signal, so you'll need to
average. That means your measurement system has to be picosecond stable
over the averaging interval.

None of those steps are particularly simple or easy.

I've worked on systems to measure the (microwave) distance to Jupiter
and back with an accuracy of around 1 part in 1E15 at 32 GHz,
integrating over 1000 seconds. That's tenths of a picosecond out of 1000
seconds. It's challenging.

http://en.wikipedia.org/wiki/Juno_%28spacecraft%29
http://juno.wisc.edu/spacecraft_instruments_GSE.html

On Thu, 17 Mar 2011 17:19:09 -0700, Jim Lux
wrote:

Certainly he predicts that the temporal dispersion is going to be 0.1ps
for near IR, which is, shall we say, challenging to measure.

Why?

measuring things to tenths of a picosecond, repeatably, can be tricky..
That's like measuring the phase difference between two 10 GHz signals
to 0.3 degrees. Or, another way to look at it is 1 picolightsecond is
about a third of a millimeter.

A third of a millimeter is no big deal and for an optical (or
sub-optical) signal - trivial. Perhaps, when stated in terms of two
10 GHz signals, "near IR" is being vastly over stated.

You're looking at
a) figuring out how to generate two signals at near IR that has a
frequency offset that can be accurately controlled.

Controlled? This is dreaming in technicolor (or near IR color) if the
source is celestial.

I thought the discussion was about dispersion, the characteristic of
the medium, not sources.

Probably some sort
of heterodyne mixing scheme would be easiest.

Heterodyning is extremely commonplace and accurate - why would it be
pondered as an alternative method?

b) sending those two signals over the optical path through
interplanetary space.

This blurs my understanding of celestial where two signals is a
poverty of what is available from ANY celestial source.

c) recovering the signals,

If there is a problem of recovery, it seems it is more a practical
matter of source selection. Given the billions of celestial sources
available, I don't understand the problem.

measuring the propagation time variation
(say, by looking at the phase difference between the modulation
signals), and then removing atmospheric effects.

Why worry about the atmosphere when you can get above it?

d) it's probably going to be a pretty weak signal, so you'll need to
average. That means your measurement system has to be picosecond stable
over the averaging interval.

OK, so I am lost. This laundry list of difficulties seems to be
prepared to anticipate failure.

Name the near IR source and defend its choice in light (no pun) of
these intractable difficulties.

None of those steps are particularly simple or easy.

I've worked on systems to measure the (microwave) distance to Jupiter
and back with an accuracy of around 1 part in 1E15 at 32 GHz,

32 GHz is what photonics would call far-far IR at roughly 3 to 4
orders of magnitude distant from "near IR."

integrating over 1000 seconds. That's tenths of a picosecond out of 1000
seconds. It's challenging.

No doubt - like trying to push a peanut up Pike's Peak with your nose.
That too has been done with challenge in mind.

How did this slip from "near IR" to 32 GHz?

73's
Richard Clark, KB7QHC

On 3/18/2011 1:16 PM, Richard Clark wrote:

How did this slip from "near IR" to 32 GHz?

Hello Richard!

I'm back, and I see the old neighborhood hasn't changed much, although I
haven't seen anything from Art - hopefully the chap hasn't had a bed turn.

Here is a question or two for those who have some doubt as to the speed
of light.

A probe recently inserted itself into orbit around Mercury. How does
some presumed superluminal velocity affect the insertion?

The idea that "we" have a transmitter on Mars notwithstanding, Jupiter
has been transmitting RF for a long time. There are enough other
spacecraft running around in our solar system, and certainly if radio
waves traveled at some other velocity than what we thought they did, it
would mean a strange and useless conspiracy to hide that fact.

Cue up the twilight zone music and grab your aluminum foil hats everyone.

- 73 de Mike N3LI -

"Mike Coslo" napisal w wiadomosci
...
On 3/18/2011 1:16 PM, Richard Clark wrote:

How did this slip from "near IR" to 32 GHz?

Hello Richard!

I'm back, and I see the old neighborhood hasn't changed much, although I
haven't seen anything from Art - hopefully the chap hasn't had a bed turn.

Here is a question or two for those who have some doubt as to the speed of
light.

A probe recently inserted itself into orbit around Mercury. How does some
presumed superluminal velocity affect the insertion?

The idea that "we" have a transmitter on Mars notwithstanding, Jupiter
has been transmitting RF for a long time. There are enough other
spacecraft running around in our solar system, and certainly if radio
waves traveled at some other velocity than what we thought they did,

Not we but you.

it would mean a strange and useless conspiracy to hide that fact.

Somebody wrote that the data from the Mars are available. But it is not easy
to find them.
S*

Szczepan Bialek wrote:

Somebody wrote that the data from the Mars are available. But it is not easy
to find them.
S*

Since data from Mars is less than 150 years ago I doubt you would read it
and I know you wouldn't understand it if you did.


--
Jim Pennino

Remove .spam.sux to reply.

On 3/19/2011 11:45 AM, Szczepan Bialek wrote:


The idea that "we" have a transmitter on Mars notwithstanding, Jupiter
has been transmitting RF for a long time. There are enough other
spacecraft running around in our solar system, and certainly if radio
waves traveled at some other velocity than what we thought they did,

Not we but you.

No, not at all. The problem with all the folks who have these strange
desires to debunk basic physics is this:

Things are connected.

When people come up with theorys/conspiracies or whatever that
sopmething we thought we knew is so completely wrong, it is a mark of
thier ignorance that they don't realize that there is more than one
thing negated if they are correct. Want a different speed of radio
compared to light - or rather I should say faster than C ? Better be
prepared to abandon most of what we already know.

So in the end, we're left with either a remarkable ignorance, willful
stupidity, a creationist agenda, or else that ever loving fun
interactive game of arguing with the computer.

- 73 de Mike N3LI -

On 3/24/2011 8:34 PM, Mike Coslo wrote:
Things are connected.

When people come up with theorys/conspiracies or whatever that
sopmething we thought we knew is so completely wrong, it is a mark of
thier ignorance that they don't realize that there is more than one
thing negated if they are correct. Want a different speed of radio
compared to light - or rather I should say faster than C ? Better be
prepared to abandon most of what we already know.

So in the end, we're left with either a remarkable ignorance, willful
stupidity, a creationist agenda, or else that ever loving fun
interactive game of arguing with the computer.

- 73 de Mike N3LI -

Wait. Are you saying Science Fiction isn't real?

Next thing you'll pull out of your hat is Divining Rods can't locate water!

Or, Bog forbid, Vaccines don't cause Autism.

tom
K0TAR

Good afternoon.
We are a group of volunteers who care about the fate of those who got into trouble.
We urge all people to help the citizens of Japan. In the Czech Republic we have organized a fundraising drive. They are very necessary for those who remained without a roof over your head. Hope very much for your help. One we can not cope with this tragedy. All the money will pass to the Embassy of Japan.
Provide a report on the use of money.
Requisites for conversion to U.S. dollars:

Account name:
Sergey Timofeev
Account number:
600 617 50 01
Bank code:
5500
IBAN:
CZ77 5500 0000 0060 0617 5001
SWIFT/BIC:
RZBCCZPP
Bank address:
Raiffeisenbank, a.s.
Hvezdova 1716/2b
Prague
Czech Republic

Answer all questions. Write to
Thank you all for your help.

"Mike Coslo" napisal w wiadomosci
...
On 3/19/2011 11:45 AM, Szczepan Bialek wrote:


The idea that "we" have a transmitter on Mars notwithstanding, Jupiter
has been transmitting RF for a long time. There are enough other
spacecraft running around in our solar system, and certainly if radio
waves traveled at some other velocity than what we thought they did,

Not we but you.

No, not at all. The problem with all the folks who have these strange
desires to debunk basic physics is this:

Things are connected.

When people come up with theorys/conspiracies or whatever that sopmething
we thought we knew is so completely wrong, it is a mark of thier ignorance
that they don't realize that there is more than one thing negated if they
are correct. Want a different speed of radio compared to light - or rather
I should say faster than C ?

We have the two C. One of them is a constant in the wave equation.
The second is a speed of light. It is different in different media and the
frequency dependent. Also in space. An example Pulsars are spinning neutron
stars that emit pulses at very regular intervals ranging from milliseconds
to seconds. Astronomers believe that the pulses are emitted simultaneously
over a wide range of frequencies. However, as observed on Earth, the
components of each pulse emitted at higher radio frequencies arrive before
those emitted at lower frequencies. This dispersion occurs because of the
ionised component of the interstellar medium, which makes the group velocity
frequency dependent.
S*

On Sat, 19 Mar 2011 07:51:45 -0500, Mike Coslo wrote:

On 3/18/2011 1:16 PM, Richard Clark wrote:

How did this slip from "near IR" to 32 GHz?

Hello Richard!

Hello Mike,

Welcome back to the Land of Odds.

The idea that "we" have a transmitter on Mars notwithstanding, Jupiter
has been transmitting RF for a long time.

Jupiter was one of my first DX goals back in the early 60s. However,
to expand upon your offering (I was wondering when anyone would
mention these sources), Earth, too, is a natural RF source (to
distinguish from the unnatural - such as stations carrying Fox Noise).

Quoting Wikipedia on Jupiter (nothing much said of the other planets
other than Earth):
"The intensity of Jovian radio emissions usually varies smoothly with
time; however, Jupiter periodically emits short and powerful bursts (S
bursts), which can outshine all other components. The total emitted
power of the DAM component is about 100 GW, while the power of all
other HOM/KOM components is about 10 GW. In comparison, the total
power of Earth's radio emissions is about 0.1 GW."

("emissions in the range 3 to 40 MHz are referred to as the decametric
radiation or DAM")

This decametric radiation would put us (returning to my quoted
question above) another several orders of magnitude beneath "near IR"
and into the "frigid IR" (a distinct irony with temperatures hovering
in the hundredths of a degree K).

73's
Richard Clark, KB7QHC