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P

Phil Hobbs

Guest
On 11/19/20 5:56 PM, Steve Wilson wrote:
Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observatory-to-be-
decommissioned-in-wake-of-cable-breaks/
RIP. Aricibo was one of the things that encouraged me to study
astronomy. They did a lot of cool stuff there.

Cheers

Phil Hobbs
(B.Sc. Astronomy & Physics, UBC \'81)

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
P

Phil Hobbs

Guest
On 11/20/20 6:10 AM, Phil Allison wrote:
Martin Brown wrote:
================


Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observatory-to-be-
decommissioned-in-wake-of-cable-breaks/


** So who is listening for \"little green men\" now ?

They only did a tiny amount of that.

** What about Ellie Arroway ?


Though they did once transmit a
signal for the LGM towards M13 back in the Carl Sagan days.

** Reply expected, any day now.

..... Phil
It\'s 2020. Ctulhu is liable to wake up much sooner. Call up and
discuss it.

https://www.youtube.com/watch?v=-DsgZ4JXXB8

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
R

Rob

Guest
bob prohaska <bp@www.zefox.net> wrote:
Let\'s just suppose we\'re searching for a signal, from somebody with instruments
like ours. No constraint on when they did the sending, could be a billion years
ago. Easy case first, we happen to guess right on which direction to look and
what kind of signal they are sending. How far away could they be and still have
enough \"brightness\" against the background noise to be recognized using 50 years
of receiver data?

Probably there should be a constraint on the baud rate, but I\'m not sure how
to word it. Maybe ten bits with 95% confidence? It does seem intuitive that
fast signals are harder to recognize than slow.....
It is possible to calculate that using Shannon\'s formula, and it is
also possible to calculate how much a signal attennuates when travelling
over a distance. The amount of noise in the receiver and the background
noise in the universe can be measured. Ther also is the \"gain\" of
the transmit- and receive antennas, which is the inverse of the solid
angle that the antenna illuminates (a high antenna gain means there
is a small solid angle so you need better pointing accuracy).

From those formulas and parameters you can calculate how much power
you need to transmit a certain number of bits/s over a certain distance.
Engineers make such calculations when designing communication systems,
e.g. for spacecraft like Voyager. And they design their systems in
such a way that they can lower the bitrate over time to compensate for
the increased distance.
 
R

Rob

Guest
bitrex <user@example.net> wrote:
The reply from even a Type I civilization (which is far more advanced
than ours), that wished to communicate, would not be subtle when it
arrives. The ability of a civilization to pull signals out of the noise
and return the call massively amplified likely scales with the civilization.

If and when a civilization like that picks up our lil signal and they
decide they have something to say in response, when the reply come back
no one\'s going to be mistaking it for anything other than what it is.
You seem to assume that \"an advanced civilization\" means that it has
found how to defy the laws of nature. Or that has other laws of nature.
 
S

server

Guest
On 21 Nov 2020 12:11:48 GMT, Rob <nomail@example.com> wrote:

bob prohaska <bp@www.zefox.net> wrote:
Let\'s just suppose we\'re searching for a signal, from somebody with instruments
like ours. No constraint on when they did the sending, could be a billion years
ago. Easy case first, we happen to guess right on which direction to look and
what kind of signal they are sending. How far away could they be and still have
enough \"brightness\" against the background noise to be recognized using 50 years
of receiver data?

Probably there should be a constraint on the baud rate, but I\'m not sure how
to word it. Maybe ten bits with 95% confidence? It does seem intuitive that
fast signals are harder to recognize than slow.....

It is possible to calculate that using Shannon\'s formula,
Shannon tells how many bits/s can be transferred with a specific
bandwidth and S/N ratio.

and it is
also possible to calculate how much a signal attennuates when travelling
over a distance. The amount of noise in the receiver and the background
noise in the universe can be measured. Ther also is the \"gain\" of
the transmit- and receive antennas, which is the inverse of the solid
angle that the antenna illuminates (a high antenna gain means there
is a small solid angle so you need better pointing accuracy).
The Friis equations
https://en.wikipedia.org/wiki/Friis_transmission_equation tells the
expected received power, when both antenna aperture areas, distance
between antennas and wavelength is known.

When looking at the formulas for a point-to-point link the shorter the
wavelength the better. Thus gamma or X-ray frequencies should be used.
Unfortunately, the galactic hydrogen attenuates much of the
wavelengths below 91 nm, so slightly longer wavelengths should be used
in UV-C.

Two Hubble size (2.5 m) telescopes could maintain a quite long
distance link.

The Arecibo size but only a few GHz reflectors are quite inadequate
for interstellar communication.
 
S

server

Guest
On 21 Nov 2020 12:15:44 GMT, Rob <nomail@example.com> wrote:

bitrex <user@example.net> wrote:
The reply from even a Type I civilization (which is far more advanced
than ours), that wished to communicate, would not be subtle when it
arrives. The ability of a civilization to pull signals out of the noise
and return the call massively amplified likely scales with the civilization.

If and when a civilization like that picks up our lil signal and they
decide they have something to say in response, when the reply come back
no one\'s going to be mistaking it for anything other than what it is.

You seem to assume that \"an advanced civilization\" means that it has
found how to defy the laws of nature. Or that has other laws of nature.
An advanced civilization interested in UHF/microwave could build much
larger antennas, especially if their gravitation is low (or using
orbital dishes).

Instead of using one large dish, it is better to use a huge array of
smaller dishes as a phased array. With sufficient computational power,
instead of generating only a single very narrow beam from the multiple
antennas, a huge number of individual beams can be created to monitor
multiple direction at once, as long as the narrow beam is within the
relative wide beam of each smallish reflector.

If the advanced civilization has a energy source and could use, say 1
GW, for each antenna in a huge antenna array, a single very narrow but
extremely powerful beam could be created.

The above doesn\'t violate any laws of physics and also the human kind
could be capable of it in a century.
 
S

server

Guest
Steve Wilson <spam@me.com> wrote in
news:XnsAC7AB6702DD0Didtokenpost@69.16.179.22:

Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observatory-
to-be- decommissioned-in-wake-of-cable-breaks/
<https://en.wikipedia.org/wiki/Five-hundred-
meter_Aperture_Spherical_Telescope>

<https://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Comparison_F
AST_Arecibo_Observatory_profiles.svg/560px-
Comparison_FAST_Arecibo_Observatory_profiles.svg.png>

short url

https://tinyurl.com/y4evomaf

https://tinyurl.com/y3oj479m
 
S

server

Guest
\"Tom Del Rosso\" <fizzbintuesday@that-google-mail-domain.com> wrote
in news:rp8e8o$gfm$1@dont-email.me:

Martin Brown wrote:

Taking potshots at nearby F,G,K type stars is a much better bet
iff we want to be noticed as non-thermal radiation. For the
period where we had high power radars and analogue TV we were
obvious to anyone looking for interesting signals with a
sensitive enough radio telescope.

The change to digital TV will be misinterpretted somewhere,
someday, as the end of our civilisation, when in fact it was the
beginning of a new era of reruns from TV\'s golden age.
+1

And even from other ages. Binge watching a series is fun.

Try Lexx, for example. Some of the episodes after they came to
Earth are pretty funny.

https://www.youtube.com/results?search_query=lexx
 
S

server

Guest
Martin Riddle <martin_rid@verizon.net> wrote in
news:rj1grf1o3dod35j704pa4j2nmougmk0hmd@4ax.com:

On Thu, 19 Nov 2020 20:28:02 -0800 (PST), Phil Allison
pallison49@gmail.com> wrote:

Steve Wilson wrote:
z.
Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observator
y-to-be- decommissioned-in-wake-of-cable-breaks/


** So who is listening for \"little green men\" now ?


..... Phil

No one. Once the little green men found and capruted Jan, they
took a hyperspace jump back to Omicron Persi 8.

Cheers
https://www.youtube.com/watch?v=m3P2GNB3BDM
 
S

server

Guest
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in
news:dddabd10-2d7a-b118-6c39-de20554cb497@electrooptical.net:

On 11/20/20 6:10 AM, Phil Allison wrote:
Martin Brown wrote:
================


Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observat
ory-to-be- decommissioned-in-wake-of-cable-breaks/


** So who is listening for \"little green men\" now ?

They only did a tiny amount of that.

** What about Ellie Arroway ?


Though they did once transmit a
signal for the LGM towards M13 back in the Carl Sagan days.

** Reply expected, any day now.

..... Phil

It\'s 2020. Ctulhu is liable to wake up much sooner. Call up and
discuss it.

https://www.youtube.com/watch?v=-DsgZ4JXXB8

Cheers

Phil Hobbs
Hahahahahaa! Watch put for his noodly appendages!
 
B

bob prohaska

Guest
upsidedown@downunder.com wrote:
The Friis equations
https://en.wikipedia.org/wiki/Friis_transmission_equation tells the
expected received power, when both antenna aperture areas, distance
between antennas and wavelength is known.
There doesn\'t seem to be any consideration of either self-noise in
the receiver, nor background noise in the environment in Friis formula.
Those would seem to be the limiting constraints in the distance at
which two Arecibo-like instruments could recognize one another. The
receiving instrument must be able to detect the sender above both
its own self-noise and the background emissions.

Perhaps the question becomes one of \"how noisy is the universe\" rather
than \"how quiet/sensitive is the best receiver\"....

Thanks for reading,

bob prohaska
 
S

server

Guest
On Sat, 21 Nov 2020 18:01:11 -0000 (UTC), bob prohaska
<bp@www.zefox.net> wrote:

upsidedown@downunder.com wrote:

The Friis equations
https://en.wikipedia.org/wiki/Friis_transmission_equation tells the
expected received power, when both antenna aperture areas, distance
between antennas and wavelength is known.


There doesn\'t seem to be any consideration of either self-noise in
the receiver, nor background noise in the environment in Friis formula.
Those would seem to be the limiting constraints in the distance at
which two Arecibo-like instruments could recognize one another. The
receiving instrument must be able to detect the sender above both
its own self-noise and the background emissions.

Perhaps the question becomes one of \"how noisy is the universe\" rather
than \"how quiet/sensitive is the best receiver\"....
The Big Bang 4 K radiation is an issue, since it comes from all
directions. The 4 K black body radiation has the peak around 1 mm, so
this affects the microwave reception.

For shorter wavelengths, the question is how many warm/hot objects
are in the beam width. Ordinary stars do not radiate much in the far
UV.

Thanks for reading,

bob prohaska
 
P

Phil Hobbs

Guest
On 11/21/20 10:44 AM, DecadentLinuxUserNumeroUno@decadence.org wrote:
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in
news:dddabd10-2d7a-b118-6c39-de20554cb497@electrooptical.net:

On 11/20/20 6:10 AM, Phil Allison wrote:
Martin Brown wrote:
================


Arecibo has reached EOL.

https://arstechnica.com/science/2020/11/famed-arecibo-observat
ory-to-be- decommissioned-in-wake-of-cable-breaks/


** So who is listening for \"little green men\" now ?

They only did a tiny amount of that.

** What about Ellie Arroway ?


Though they did once transmit a
signal for the LGM towards M13 back in the Carl Sagan days.

** Reply expected, any day now.

..... Phil

It\'s 2020. Ctulhu is liable to wake up much sooner. Call up and
discuss it.

https://www.youtube.com/watch?v=-DsgZ4JXXB8

Cheers

Phil Hobbs


Hahahahahaa! Watch put for his noodly appendages!
Welcome back. How long is your parole? ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
T

Tom Del Rosso

Guest
Phil Hobbs wrote:
It\'s 2020. Ctulhu is liable to wake up much sooner. Call up and
discuss it.

https://www.youtube.com/watch?v=-DsgZ4JXXB8
Have you seen the movie from 2005? It\'s excellent in spite of it\'s
short length.

https://www.imdb.com/title/tt0478988/

It was on Hulu in 2013 but I don\'t know where you can view it now.
 
P

Phil Hobbs

Guest
On 11/21/20 7:28 PM, Tom Del Rosso wrote:
Phil Hobbs wrote:

It\'s 2020. Ctulhu is liable to wake up much sooner. Call up and
discuss it.

https://www.youtube.com/watch?v=-DsgZ4JXXB8


Have you seen the movie from 2005? It\'s excellent in spite of it\'s
short length.

https://www.imdb.com/title/tt0478988/

It was on Hulu in 2013 but I don\'t know where you can view it now.
Nah, I haven\'t watched a movie in over 30 years, apart from a private
showing of a documentary about the family of a good friend.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
R

Rickster C

Guest
On Saturday, November 21, 2020 at 10:32:36 AM UTC-5, DecadentLinux...@decadence.org wrote:
\"Tom Del Rosso\" <fizzbin...@that-google-mail-domain.com> wrote
in news:rp8e8o$gfm$1...@dont-email.me:
Martin Brown wrote:

Taking potshots at nearby F,G,K type stars is a much better bet
iff we want to be noticed as non-thermal radiation. For the
period where we had high power radars and analogue TV we were
obvious to anyone looking for interesting signals with a
sensitive enough radio telescope.

The change to digital TV will be misinterpretted somewhere,
someday, as the end of our civilisation, when in fact it was the
beginning of a new era of reruns from TV\'s golden age.

+1

And even from other ages. Binge watching a series is fun.

Try Lexx, for example. Some of the episodes after they came to
Earth are pretty funny.

https://www.youtube.com/results?search_query=lexx
Futurama has a character Lrrr, ruler of the planet Omicron Persei 8, who watches an Earth TV series that, coincidentally, arrives at his planet 1,000 years after broadcast from Earth. When the show is interrupted by Fry (of course), 1000 years later Lrrr is infuriated and attacks Earth insisting they complete the performance. I\'ll let you find the rest. Lrrr likes to binge watch Friends too.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209
 
B

bitrex

Guest
On 11/21/2020 10:32 AM, DecadentLinuxUserNumeroUno@decadence.org wrote:
\"Tom Del Rosso\" <fizzbintuesday@that-google-mail-domain.com> wrote
in news:rp8e8o$gfm$1@dont-email.me:

Martin Brown wrote:

Taking potshots at nearby F,G,K type stars is a much better bet
iff we want to be noticed as non-thermal radiation. For the
period where we had high power radars and analogue TV we were
obvious to anyone looking for interesting signals with a
sensitive enough radio telescope.

The change to digital TV will be misinterpretted somewhere,
someday, as the end of our civilisation, when in fact it was the
beginning of a new era of reruns from TV\'s golden age.


+1

And even from other ages. Binge watching a series is fun.

Try Lexx, for example. Some of the episodes after they came to
Earth are pretty funny.

https://www.youtube.com/results?search_query=lexx
They will assume our civilization is going through that phase where it
takes 25 years to evolve from OTA broadcast TV to a form of
entertainment delivered over terrestrial links that\'s pretty much the
same except you watch the shows on a computer. and you can pick what
shows you wanna watch when.

25 years to make this technological breakthrough. They\'ll then change
the encyclopedia galactica entry back from \"mostly harmless\" to \"harmless\"
 
M

Martin Brown

Guest
On 20/11/2020 13:01, Tom Del Rosso wrote:
Martin Brown wrote:

It is a shame to lose a grand old instrument even if it could only
look at a fraction of the sky around the zenith it was a *very* big
dish.

Something farther from the equator could scan a lot more sky even if was
also a stationary dish. Why did we put it in Puerto Rico?
The stripe of sky you can see varies with latitude like Cos(latitude) so
near the equator is about as good as you can get for maximising utility.
I think that finding a crater with almost the right shape played a part.

Think about what would happen at the pole...

The Greenbank telescope collapse (big steerable dish) was much more
devastating. The observer in the control room was very very lucky!

https://public.nrao.edu/gallery/the-collapsed-300foot-telescope/

https://www.nytimes.com/1988/11/17/us/giant-telescope-collapses-big-us-research-setback.html

The telescope sadly ended its life as a twisted heap of scrap metal.

--
Regards,
Martin Brown
 
S

Steve Wilson

Guest
Martin Brown <\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 20/11/2020 13:01, Tom Del Rosso wrote:
Martin Brown wrote:

It is a shame to lose a grand old instrument even if it could only
look at a fraction of the sky around the zenith it was a *very* big
dish.

Something farther from the equator could scan a lot more sky even if
was also a stationary dish. Why did we put it in Puerto Rico?

The stripe of sky you can see varies with latitude like Cos(latitude)
so near the equator is about as good as you can get for maximising
utility. I think that finding a crater with almost the right shape
played a part.

Think about what would happen at the pole...

The Greenbank telescope collapse (big steerable dish) was much more
devastating. The observer in the control room was very very lucky!

https://public.nrao.edu/gallery/the-collapsed-300foot-telescope/

https://www.nytimes.com/1988/11/17/us/giant-telescope-collapses-big-us-
research-setback.html

The telescope sadly ended its life as a twisted heap of scrap metal.
They fixed it. Bigger and better

https://en.wikipedia.org/wiki/Green_Bank_Telescope



--
Science teaches us to trust. - sw
 
M

Martin Brown

Guest
On 20/11/2020 18:38, bob prohaska wrote:
Tom Del Rosso <fizzbintuesday@that-google-mail-domain.com> wrote:
Martin Brown wrote:

It is a shame to lose a grand old instrument even if it could only
look at a fraction of the sky around the zenith it was a *very* big
dish.

Something farther from the equator could scan a lot more sky even if was
also a stationary dish. Why did we put it in Puerto Rico?

Probably, cost. It\'s built into a natural cavity in the ground. I believe
the new Chinese instrument is constructed similarly.

An aside: Over what distance could two Arecibo-like instruments communicate if
A) they knew where to look and what to look for
A considerable distance although if you knew that much detail you might
well build a phased array to do it rather than use a single dish.

> B) they knew only where to look, but not what to look for

I\'m not sure how they could be in that position since to know where to
look someone would have had to tell them!

C) They knew not where to look and not what to look for
D) they knew not where to look, but did know what to look for
C&D are more or less the same problem and looking for stars where the
radio emissions are distinctly non-thermal, polarised and have
periodicities in the could be a frame rate zone of say 10-100 FPS would
be good hunting territory. It also coincides with naturally occurring
pulsars which when first detected at Cambridge were labelled LGM on the
chart recording!

In actuality the pulsar surveys look for stuff on a much wider range
than that since they don\'t know for sure what the ultimate bounds on
pulsar spin rates actually are.

https://en.wikipedia.org/wiki/PSR_B1919%2B21

Millisecond pulsars were missed until the kit and inspired data
processing improvements became good enough to see them.

https://en.wikipedia.org/wiki/PSR_B1937%2B21

Snag is that if we are any guide a civilisation will only be obviously
radio bright from the point where they can build high power transmitters
to the time when they master spread spectrum and fibre technologies.

The answers doubtless depend on time allocated to the search.
Let\'s assume 50 years, the approximate life of the instrument.

I\'ve done a little web-surfing and found no explicit discussions.
The answers might have some bearing on Fermi\'s paradox.
I\'m not sure how far out an Arecibo class telescope could detect a clone
of itself if they were facing each other. The SETI guys have given
considerable thought to exactly what frequency(s) to transmit on to get
the greatest possible range and stand out as non-natural emission.

The so called \"water hole\" is a favourite for SETI transmissions and
passive listening (on the assumption that all scientists think alike).

https://www.seti.org/seti-institute/project/details/seti-observations

A narrowband CW signal with near 100% linear polarisation pulsed in a
binary pattern will attract attention if seen by a scientist. Somewhere
in the window between 1 & 10GHz being probably the optimum depending on
the figure of the dish and the power of the transmitter.

--
Regards,
Martin Brown
 
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