SETI: call to arms!

Rob,

"Rob Dekker" wrote in message
m...

"Alfred A. Aburto Jr." wrote in message
. com...
....
The most powerful sources are radars. They operate all over the 1-100
GHz
band. Long range radars operate in the so-called "L-Band" which runs
from 1
to 2 GHz. There are also "S-Band" radars in the 2-4 GHz ("C-Band is
4-8GHz,
..., "O Band" is 60-90GHz) ... notice that the L-Band radar covers the
water-hole region near 1.420406 GHz.

Radars are used for many purposes and they are found around the world
operating day and night ...

I'm almost ("almost" because I'm lacking specific and sufficient data)
certain that, say, the Parkes (210 ft? diameter) radio telescope could
detect emissions from an equivalent Earth place at the distance of Alpha
Centauri.

Well, Here goes. Use seti FAQ formula :

If we have a 300ft diameter dish (radius==50m), receiving a signal
from 5 LYs (Alpha Centauri) away, and lets assume we need 10dB S/N ratio
to make it recognizable, with receiver system temp of about 100K (pretty
good receiver in microwave), then the transmitter needs to radiate with
40GW EIRP.

That is assuming it is a CW pulse (not modulated, only one pulse), and
that we are
using all information in the signal, so that a 1ms pulse of this power (by
definition at
least 1kHz wide) will not go unnoticed.
I'm not sure if such pulses would go by unnoticed by seti@home. Do you
know ?

40GW EIRP.

I don't know enough about radar to tell you if that is frequently used
here on
earth, and for which purpose, but to radiate that around 1.4GHz you need a
lot of line-power, (10's or 100's of KW's) and a pretty decent size dish
(10's of meters).
A airtraffic control radar signal will not make it I think.

So only radar for very special applications (military high-sensitivity
radar) or
astroid radar would create that amount of power. And these are not
transmitting
too frequently. And thus the signal would not be 'reproducable', and thus
we can't prove or dis-prove if the signal is actually artificial and from
Alpha Centauri.

So I think we can't detect a earth-like civilisation even it there is one
around Alpha Centauri.

..
snipsnap

Ah! So you read the FAQ. Humm :-) That's great!

I'll check into this too ...
(I wish I knew more about military radars myself ... space surviellance
radars for example)

You're right though, sounds like a special radar is needed.

Arecibo, of course, is a very special radar and very powerful one too used
in part for pinging off Solar System objects (planets, asteroids...)
(100 KW omni power isn't much though generally speaking nowadays)

(Arecibo, I think, transmits at 1-10 Megawatts ...it "can" put 10's of
terrawatts of power in a narrowband beam)
I wouln't count Arecibo though, because the odds of detection, even with
great SNR, would be very slim (one might need to look our way for ages
before one saw a ping ...)

I distinctly remember that some of the military radars could be detected 100
LY's away ... but I'll recheck all this ...

I'll get back here soon ...
Al

"Alfred A. Aburto Jr." wrote in message om...
Rob,

"Rob Dekker" wrote in message
m...

"Alfred A. Aburto Jr." wrote in message
. com...
....
The most powerful sources are radars. They operate all over the 1-100
GHz
band. Long range radars operate in the so-called "L-Band" which runs
from 1
to 2 GHz. There are also "S-Band" radars in the 2-4 GHz ("C-Band is
4-8GHz,
..., "O Band" is 60-90GHz) ... notice that the L-Band radar covers the
water-hole region near 1.420406 GHz.

Radars are used for many purposes and they are found around the world
operating day and night ...

I'm almost ("almost" because I'm lacking specific and sufficient data)
certain that, say, the Parkes (210 ft? diameter) radio telescope could
detect emissions from an equivalent Earth place at the distance of Alpha
Centauri.

Well, Here goes. Use seti FAQ formula :

If we have a 300ft diameter dish (radius==50m), receiving a signal
from 5 LYs (Alpha Centauri) away, and lets assume we need 10dB S/N ratio
to make it recognizable, with receiver system temp of about 100K (pretty
good receiver in microwave), then the transmitter needs to radiate with
40GW EIRP.

That is assuming it is a CW pulse (not modulated, only one pulse), and
that we are
using all information in the signal, so that a 1ms pulse of this power (by
definition at
least 1kHz wide) will not go unnoticed.
I'm not sure if such pulses would go by unnoticed by seti@home. Do you
know ?

40GW EIRP.

I don't know enough about radar to tell you if that is frequently used
here on
earth, and for which purpose, but to radiate that around 1.4GHz you need a
lot of line-power, (10's or 100's of KW's) and a pretty decent size dish
(10's of meters).
A airtraffic control radar signal will not make it I think.

So only radar for very special applications (military high-sensitivity
radar) or
astroid radar would create that amount of power. And these are not
transmitting
too frequently. And thus the signal would not be 'reproducable', and thus
we can't prove or dis-prove if the signal is actually artificial and from
Alpha Centauri.

So I think we can't detect a earth-like civilisation even it there is one
around Alpha Centauri.

..
snipsnap

Ah! So you read the FAQ. Humm :-) That's great!

I'll check into this too ...
(I wish I knew more about military radars myself ... space surviellance
radars for example)

You're right though, sounds like a special radar is needed.

Arecibo, of course, is a very special radar and very powerful one too used
in part for pinging off Solar System objects (planets, asteroids...)
(100 KW omni power isn't much though generally speaking nowadays)

(Arecibo, I think, transmits at 1-10 Megawatts ...it "can" put 10's of
terrawatts of power in a narrowband beam)
I wouln't count Arecibo though, because the odds of detection, even with
great SNR, would be very slim (one might need to look our way for ages
before one saw a ping ...)

I distinctly remember that some of the military radars could be detected 100
LY's away ... but I'll recheck all this ...

I'll get back here soon ...
Al


Yeah. We need to know more about radar, and the signals they produce
(frequency/power/modulation/rotation speed etc). I dont know enough about that.

I'm sure there are some radar systems which indeed transmit in this 40GW EIRP range.
Arecibo will easily be able to do that, but only points at a fixed point in the sky
twice a year or so. Not much repetition for any ET that is listening.

So the question is how many of these high-power radar systems are actually operating
say, on a dayly basis, and how often their beam points to an fixed point in the sky.
That would say something about the probability that a high-power transmitter
actually points at us (again assuming an earth-like civilisation 5 LYs away).

The other thing that is interesting is the 'application' for these high-power radar's.
If ET is smart, they will find an optimal frequency band, and optimal modulation
technique/bandwidth/pulse, and optimal sky-coverage repetition rate depending on
the application they have in mind. An astroid radar for example would not need to
cover the sky more often than once/day, but needs deep space (sensitive) detection
requirements. Also the reflected signal will take minutes to hours to return, which
also impacts the design of the system.
We need a radar expert to give us some better idea of trade-offs of
what kind of signal we could expect to hear from what kind of application.

We know from previous SETI's (project Phoenix etc) that there are no obvious,
super-loud microwave signals out there. And beacons are also hard to find.
At least around 1.42 GHz. But we do not produce super-loud microwave signals,
and we also don't have a beacon round 1.42 GHz. So why would ET have that ?
Maybe it is time to focus on applications that ET really could use, and then
figure out how the signals of these applications would sound like here, and where
we could find them in the spectrum.

If in the end it turns out that we would need to build a $100B device to detect
(with some certainty) a civilisation of our own level within a 1000LY range from earth,
but it would only take $10B to build a device which can detect (with some certainty)
oxygen on planets in a 1000LY range, then I'd put my money in the oxygen detector first...)
Now we've come full-circle on the science and funding aspects of SETI.

"Alfred A. Aburto Jr." wrote in message om...
Rob,

"Rob Dekker" wrote in message
m...

"Alfred A. Aburto Jr." wrote in message
. com...
....
The most powerful sources are radars. They operate all over the 1-100
GHz
band. Long range radars operate in the so-called "L-Band" which runs
from 1
to 2 GHz. There are also "S-Band" radars in the 2-4 GHz ("C-Band is
4-8GHz,
..., "O Band" is 60-90GHz) ... notice that the L-Band radar covers the
water-hole region near 1.420406 GHz.

Radars are used for many purposes and they are found around the world
operating day and night ...

I'm almost ("almost" because I'm lacking specific and sufficient data)
certain that, say, the Parkes (210 ft? diameter) radio telescope could
detect emissions from an equivalent Earth place at the distance of Alpha
Centauri.

Well, Here goes. Use seti FAQ formula :

If we have a 300ft diameter dish (radius==50m), receiving a signal
from 5 LYs (Alpha Centauri) away, and lets assume we need 10dB S/N ratio
to make it recognizable, with receiver system temp of about 100K (pretty
good receiver in microwave), then the transmitter needs to radiate with
40GW EIRP.

That is assuming it is a CW pulse (not modulated, only one pulse), and
that we are
using all information in the signal, so that a 1ms pulse of this power (by
definition at
least 1kHz wide) will not go unnoticed.
I'm not sure if such pulses would go by unnoticed by seti@home. Do you
know ?

40GW EIRP.

I don't know enough about radar to tell you if that is frequently used
here on
earth, and for which purpose, but to radiate that around 1.4GHz you need a
lot of line-power, (10's or 100's of KW's) and a pretty decent size dish
(10's of meters).
A airtraffic control radar signal will not make it I think.

So only radar for very special applications (military high-sensitivity
radar) or
astroid radar would create that amount of power. And these are not
transmitting
too frequently. And thus the signal would not be 'reproducable', and thus
we can't prove or dis-prove if the signal is actually artificial and from
Alpha Centauri.

So I think we can't detect a earth-like civilisation even it there is one
around Alpha Centauri.

..
snipsnap

Ah! So you read the FAQ. Humm :-) That's great!

I'll check into this too ...
(I wish I knew more about military radars myself ... space surviellance
radars for example)

You're right though, sounds like a special radar is needed.

Arecibo, of course, is a very special radar and very powerful one too used
in part for pinging off Solar System objects (planets, asteroids...)
(100 KW omni power isn't much though generally speaking nowadays)

(Arecibo, I think, transmits at 1-10 Megawatts ...it "can" put 10's of
terrawatts of power in a narrowband beam)
I wouln't count Arecibo though, because the odds of detection, even with
great SNR, would be very slim (one might need to look our way for ages
before one saw a ping ...)

I distinctly remember that some of the military radars could be detected 100
LY's away ... but I'll recheck all this ...

I'll get back here soon ...
Al


Yeah. We need to know more about radar, and the signals they produce
(frequency/power/modulation/rotation speed etc). I dont know enough about that.

I'm sure there are some radar systems which indeed transmit in this 40GW EIRP range.
Arecibo will easily be able to do that, but only points at a fixed point in the sky
twice a year or so. Not much repetition for any ET that is listening.

So the question is how many of these high-power radar systems are actually operating
say, on a dayly basis, and how often their beam points to an fixed point in the sky.
That would say something about the probability that a high-power transmitter
actually points at us (again assuming an earth-like civilisation 5 LYs away).

The other thing that is interesting is the 'application' for these high-power radar's.
If ET is smart, they will find an optimal frequency band, and optimal modulation
technique/bandwidth/pulse, and optimal sky-coverage repetition rate depending on
the application they have in mind. An astroid radar for example would not need to
cover the sky more often than once/day, but needs deep space (sensitive) detection
requirements. Also the reflected signal will take minutes to hours to return, which
also impacts the design of the system.
We need a radar expert to give us some better idea of trade-offs of
what kind of signal we could expect to hear from what kind of application.

We know from previous SETI's (project Phoenix etc) that there are no obvious,
super-loud microwave signals out there. And beacons are also hard to find.
At least around 1.42 GHz. But we do not produce super-loud microwave signals,
and we also don't have a beacon round 1.42 GHz. So why would ET have that ?
Maybe it is time to focus on applications that ET really could use, and then
figure out how the signals of these applications would sound like here, and where
we could find them in the spectrum.

If in the end it turns out that we would need to build a $100B device to detect
(with some certainty) a civilisation of our own level within a 1000LY range from earth,
but it would only take $10B to build a device which can detect (with some certainty)
oxygen on planets in a 1000LY range, then I'd put my money in the oxygen detector first...)
Now we've come full-circle on the science and funding aspects of SETI.

"Rob Dekker" wrote in message
m...

"Alfred A. Aburto Jr." wrote in message
om...
Rob,

"Rob Dekker" wrote in message
m...

"Alfred A. Aburto Jr." wrote in message
. com...
....
The most powerful sources are radars. They operate all over the
1-100
GHz
band. Long range radars operate in the so-called "L-Band" which runs
from 1
to 2 GHz. There are also "S-Band" radars in the 2-4 GHz ("C-Band is
4-8GHz,
..., "O Band" is 60-90GHz) ... notice that the L-Band radar covers
the
water-hole region near 1.420406 GHz.

Radars are used for many purposes and they are found around the
world
operating day and night ...

I'm almost ("almost" because I'm lacking specific and sufficient
data)
certain that, say, the Parkes (210 ft? diameter) radio telescope
could
detect emissions from an equivalent Earth place at the distance of
Alpha
Centauri.

Well, Here goes. Use seti FAQ formula :

If we have a 300ft diameter dish (radius==50m), receiving a signal
from 5 LYs (Alpha Centauri) away, and lets assume we need 10dB S/N
ratio
to make it recognizable, with receiver system temp of about 100K
(pretty
good receiver in microwave), then the transmitter needs to radiate
with
40GW EIRP.

That is assuming it is a CW pulse (not modulated, only one pulse), and
that we are
using all information in the signal, so that a 1ms pulse of this power
(by
definition at
least 1kHz wide) will not go unnoticed.
I'm not sure if such pulses would go by unnoticed by seti@home. Do you
know ?

40GW EIRP.

I don't know enough about radar to tell you if that is frequently used
here on
earth, and for which purpose, but to radiate that around 1.4GHz you
need a
lot of line-power, (10's or 100's of KW's) and a pretty decent size
dish
(10's of meters).
A airtraffic control radar signal will not make it I think.

So only radar for very special applications (military high-sensitivity
radar) or
astroid radar would create that amount of power. And these are not
transmitting
too frequently. And thus the signal would not be 'reproducable', and
thus
we can't prove or dis-prove if the signal is actually artificial and
from
Alpha Centauri.

So I think we can't detect a earth-like civilisation even it there is
one
around Alpha Centauri.

..
snipsnap

Ah! So you read the FAQ. Humm :-) That's great!

I'll check into this too ...
(I wish I knew more about military radars myself ... space surviellance
radars for example)

You're right though, sounds like a special radar is needed.

Arecibo, of course, is a very special radar and very powerful one too
used
in part for pinging off Solar System objects (planets, asteroids...)
(100 KW omni power isn't much though generally speaking nowadays)

(Arecibo, I think, transmits at 1-10 Megawatts ...it "can" put 10's of
terrawatts of power in a narrowband beam)
I wouln't count Arecibo though, because the odds of detection, even with
great SNR, would be very slim (one might need to look our way for ages
before one saw a ping ...)

I distinctly remember that some of the military radars could be detected
100
LY's away ... but I'll recheck all this ...

I'll get back here soon ...
Al


Yeah. We need to know more about radar, and the signals they produce
(frequency/power/modulation/rotation speed etc). I dont know enough about
that.

I'm sure there are some radar systems which indeed transmit in this 40GW
EIRP range.
Arecibo will easily be able to do that, but only points at a fixed point
in the sky
twice a year or so. Not much repetition for any ET that is listening.

So the question is how many of these high-power radar systems are actually
operating
say, on a dayly basis, and how often their beam points to an fixed point
in the sky.
That would say something about the probability that a high-power
transmitter
actually points at us (again assuming an earth-like civilisation 5 LYs
away).

So, we're not so sure we could detect ourselves (@4 LY's) or not maybe?
There is a possibility, but one would need to look our way an awfully long
time. How long I wonder? What are the real probability of detection
statistics? That is my question ...
(rats!, need to leave ... talk more later ...)


The other thing that is interesting is the 'application' for these
high-power radar's.
If ET is smart, they will find an optimal frequency band, and optimal
modulation
technique/bandwidth/pulse, and optimal sky-coverage repetition rate
depending on
the application they have in mind. An astroid radar for example would not
need to
cover the sky more often than once/day, but needs deep space (sensitive)
detection
requirements. Also the reflected signal will take minutes to hours to
return, which
also impacts the design of the system.
We need a radar expert to give us some better idea of trade-offs of
what kind of signal we could expect to hear from what kind of application.

We know from previous SETI's (project Phoenix etc) that there are no
obvious,
super-loud microwave signals out there. And beacons are also hard to find.
At least around 1.42 GHz. But we do not produce super-loud microwave
signals,
and we also don't have a beacon round 1.42 GHz. So why would ET have that
?
Maybe it is time to focus on applications that ET really could use, and
then
figure out how the signals of these applications would sound like here,
and where
we could find them in the spectrum.

If in the end it turns out that we would need to build a $100B device to
detect
(with some certainty) a civilisation of our own level within a 1000LY
range from earth,
but it would only take $10B to build a device which can detect (with some
certainty)
oxygen on planets in a 1000LY range, then I'd put my money in the oxygen
detector first...)
Now we've come full-circle on the science and funding aspects of SETI.

"Rob Dekker" wrote in message
m...

"Alfred A. Aburto Jr." wrote in message
om...
Rob,

"Rob Dekker" wrote in message
m...

"Alfred A. Aburto Jr." wrote in message
. com...
....
The most powerful sources are radars. They operate all over the
1-100
GHz
band. Long range radars operate in the so-called "L-Band" which runs
from 1
to 2 GHz. There are also "S-Band" radars in the 2-4 GHz ("C-Band is
4-8GHz,
..., "O Band" is 60-90GHz) ... notice that the L-Band radar covers
the
water-hole region near 1.420406 GHz.

Radars are used for many purposes and they are found around the
world
operating day and night ...

I'm almost ("almost" because I'm lacking specific and sufficient
data)
certain that, say, the Parkes (210 ft? diameter) radio telescope
could
detect emissions from an equivalent Earth place at the distance of
Alpha
Centauri.

Well, Here goes. Use seti FAQ formula :

If we have a 300ft diameter dish (radius==50m), receiving a signal
from 5 LYs (Alpha Centauri) away, and lets assume we need 10dB S/N
ratio
to make it recognizable, with receiver system temp of about 100K
(pretty
good receiver in microwave), then the transmitter needs to radiate
with
40GW EIRP.

That is assuming it is a CW pulse (not modulated, only one pulse), and
that we are
using all information in the signal, so that a 1ms pulse of this power
(by
definition at
least 1kHz wide) will not go unnoticed.
I'm not sure if such pulses would go by unnoticed by seti@home. Do you
know ?

40GW EIRP.

I don't know enough about radar to tell you if that is frequently used
here on
earth, and for which purpose, but to radiate that around 1.4GHz you
need a
lot of line-power, (10's or 100's of KW's) and a pretty decent size
dish
(10's of meters).
A airtraffic control radar signal will not make it I think.

So only radar for very special applications (military high-sensitivity
radar) or
astroid radar would create that amount of power. And these are not
transmitting
too frequently. And thus the signal would not be 'reproducable', and
thus
we can't prove or dis-prove if the signal is actually artificial and
from
Alpha Centauri.

So I think we can't detect a earth-like civilisation even it there is
one
around Alpha Centauri.

..
snipsnap

Ah! So you read the FAQ. Humm :-) That's great!

I'll check into this too ...
(I wish I knew more about military radars myself ... space surviellance
radars for example)

You're right though, sounds like a special radar is needed.

Arecibo, of course, is a very special radar and very powerful one too
used
in part for pinging off Solar System objects (planets, asteroids...)
(100 KW omni power isn't much though generally speaking nowadays)

(Arecibo, I think, transmits at 1-10 Megawatts ...it "can" put 10's of
terrawatts of power in a narrowband beam)
I wouln't count Arecibo though, because the odds of detection, even with
great SNR, would be very slim (one might need to look our way for ages
before one saw a ping ...)

I distinctly remember that some of the military radars could be detected
100
LY's away ... but I'll recheck all this ...

I'll get back here soon ...
Al


Yeah. We need to know more about radar, and the signals they produce
(frequency/power/modulation/rotation speed etc). I dont know enough about
that.

I'm sure there are some radar systems which indeed transmit in this 40GW
EIRP range.
Arecibo will easily be able to do that, but only points at a fixed point
in the sky
twice a year or so. Not much repetition for any ET that is listening.

So the question is how many of these high-power radar systems are actually
operating
say, on a dayly basis, and how often their beam points to an fixed point
in the sky.
That would say something about the probability that a high-power
transmitter
actually points at us (again assuming an earth-like civilisation 5 LYs
away).

So, we're not so sure we could detect ourselves (@4 LY's) or not maybe?
There is a possibility, but one would need to look our way an awfully long
time. How long I wonder? What are the real probability of detection
statistics? That is my question ...
(rats!, need to leave ... talk more later ...)


The other thing that is interesting is the 'application' for these
high-power radar's.
If ET is smart, they will find an optimal frequency band, and optimal
modulation
technique/bandwidth/pulse, and optimal sky-coverage repetition rate
depending on
the application they have in mind. An astroid radar for example would not
need to
cover the sky more often than once/day, but needs deep space (sensitive)
detection
requirements. Also the reflected signal will take minutes to hours to
return, which
also impacts the design of the system.
We need a radar expert to give us some better idea of trade-offs of
what kind of signal we could expect to hear from what kind of application.

We know from previous SETI's (project Phoenix etc) that there are no
obvious,
super-loud microwave signals out there. And beacons are also hard to find.
At least around 1.42 GHz. But we do not produce super-loud microwave
signals,
and we also don't have a beacon round 1.42 GHz. So why would ET have that
?
Maybe it is time to focus on applications that ET really could use, and
then
figure out how the signals of these applications would sound like here,
and where
we could find them in the spectrum.

If in the end it turns out that we would need to build a $100B device to
detect
(with some certainty) a civilisation of our own level within a 1000LY
range from earth,
but it would only take $10B to build a device which can detect (with some
certainty)
oxygen on planets in a 1000LY range, then I'd put my money in the oxygen
detector first...)
Now we've come full-circle on the science and funding aspects of SETI.

Rob,

[snip,snip]

Ah! So you read the FAQ. Humm :-) That's great!

I'll check into this too ...
(I wish I knew more about military radars myself ... space surviellance
radars for example)

You're right though, sounds like a special radar is needed.

Arecibo, of course, is a very special radar and very powerful one too
used
in part for pinging off Solar System objects (planets, asteroids...)
(100 KW omni power isn't much though generally speaking nowadays)

(Arecibo, I think, transmits at 1-10 Megawatts ...it "can" put 10's of
terrawatts of power in a narrowband beam)
I wouln't count Arecibo though, because the odds of detection, even with
great SNR, would be very slim (one might need to look our way for ages
before one saw a ping ...)

I distinctly remember that some of the military radars could be detected
100
LY's away ... but I'll recheck all this ...

I'll get back here soon ...
Al


Yeah. We need to know more about radar, and the signals they produce
(frequency/power/modulation/rotation speed etc). I dont know enough about
that.

I'm sure there are some radar systems which indeed transmit in this 40GW
EIRP range.
Arecibo will easily be able to do that, but only points at a fixed point
in the sky
twice a year or so. Not much repetition for any ET that is listening.

So the question is how many of these high-power radar systems are actually
operating
say, on a dayly basis, and how often their beam points to an fixed point
in the sky.
That would say something about the probability that a high-power
transmitter
actually points at us (again assuming an earth-like civilisation 5 LYs
away).

The other thing that is interesting is the 'application' for these
high-power radar's.
If ET is smart, they will find an optimal frequency band, and optimal
modulation
technique/bandwidth/pulse, and optimal sky-coverage repetition rate
depending on
the application they have in mind. An astroid radar for example would not
need to
cover the sky more often than once/day, but needs deep space (sensitive)
detection
requirements. Also the reflected signal will take minutes to hours to
return, which
also impacts the design of the system.
We need a radar expert to give us some better idea of trade-offs of
what kind of signal we could expect to hear from what kind of application.

We know from previous SETI's (project Phoenix etc) that there are no
obvious,
super-loud microwave signals out there.

Wait a minute! We were just talking about how difficult it is to detect even
with a powerful radar or whatever!
I claim you can't make that claim (this statement is far from proven: "there
are no obvious, super-loud microwave signals out there.") ... First of all
Project Phoenix has only looked at several hundreds of stars ... they didn't
do an all sky search ... they only looked for a few hours at each star ...
what is the probability they missed something? I'd bet instead that their
certainty of "no one there" for those stars they have searched (to say
nothing of those billions and billions of other stars in the Galaxy) is low
to very low. Same for seti@home. Same for project META and Project BETA. I
hope that these scientists someday get down to the nitty gritty and figure
out what the real odds of detection are ....

Heck, I'll be dead in 20 years! :-) ... can't wait too much longer! :-) ...
all I can do is beat the bushes hoping that someone wakes up soon :-)

You're sort of right though. There doesn't appear to be really big
techological civilizations out there --- nothing really obvious ... it does
seem quiet out there. What I'd like to know though, clearly, is that due to
the fact that the probability of detection is so very very poor or is it due
to the fact that there _really_ isn't anyone out there. How can one model
this so that one can begin to understand? If I was at Mars for example and
looked back at Earth and did a spectrum analysis for say days (a week or two
perhaps) what would I see from Earth in terms of electromagnetic energy?
What do we look like? What's Earth's EM signature like? Once we know this,
then how far away could we detect Earth given some fixed resources (antenna
size, etc. ...)?

And beacons are also hard to find.

Yes ..

At least around 1.42 GHz. But we do not produce super-loud microwave
signals,

Arecibo does ...
Maybe others too ...

and we also don't have a beacon round 1.42 GHz. So why would ET have that
?

There have been a few Russian transmissions of signals to specific stars (or
areas in space say) ...

Maybe it is time to focus on applications that ET really could use, and
then
figure out how the signals of these applications would sound like here,
and where
we could find them in the spectrum.

If in the end it turns out that we would need to build a $100B device to
detect
(with some certainty) a civilisation of our own level within a 1000LY
range from earth,
but it would only take $10B to build a device which can detect (with some
certainty)
oxygen on planets in a 1000LY range, then I'd put my money in the oxygen
detector first...)

Sounds reasonable doesn't it. SETI is on the fringe ...

Now we've come full-circle on the science and funding aspects of SETI.

Rob,

[snip,snip]

Ah! So you read the FAQ. Humm :-) That's great!

I'll check into this too ...
(I wish I knew more about military radars myself ... space surviellance
radars for example)

You're right though, sounds like a special radar is needed.

Arecibo, of course, is a very special radar and very powerful one too
used
in part for pinging off Solar System objects (planets, asteroids...)
(100 KW omni power isn't much though generally speaking nowadays)

(Arecibo, I think, transmits at 1-10 Megawatts ...it "can" put 10's of
terrawatts of power in a narrowband beam)
I wouln't count Arecibo though, because the odds of detection, even with
great SNR, would be very slim (one might need to look our way for ages
before one saw a ping ...)

I distinctly remember that some of the military radars could be detected
100
LY's away ... but I'll recheck all this ...

I'll get back here soon ...
Al


Yeah. We need to know more about radar, and the signals they produce
(frequency/power/modulation/rotation speed etc). I dont know enough about
that.

I'm sure there are some radar systems which indeed transmit in this 40GW
EIRP range.
Arecibo will easily be able to do that, but only points at a fixed point
in the sky
twice a year or so. Not much repetition for any ET that is listening.

So the question is how many of these high-power radar systems are actually
operating
say, on a dayly basis, and how often their beam points to an fixed point
in the sky.
That would say something about the probability that a high-power
transmitter
actually points at us (again assuming an earth-like civilisation 5 LYs
away).

The other thing that is interesting is the 'application' for these
high-power radar's.
If ET is smart, they will find an optimal frequency band, and optimal
modulation
technique/bandwidth/pulse, and optimal sky-coverage repetition rate
depending on
the application they have in mind. An astroid radar for example would not
need to
cover the sky more often than once/day, but needs deep space (sensitive)
detection
requirements. Also the reflected signal will take minutes to hours to
return, which
also impacts the design of the system.
We need a radar expert to give us some better idea of trade-offs of
what kind of signal we could expect to hear from what kind of application.

We know from previous SETI's (project Phoenix etc) that there are no
obvious,
super-loud microwave signals out there.

Wait a minute! We were just talking about how difficult it is to detect even
with a powerful radar or whatever!
I claim you can't make that claim (this statement is far from proven: "there
are no obvious, super-loud microwave signals out there.") ... First of all
Project Phoenix has only looked at several hundreds of stars ... they didn't
do an all sky search ... they only looked for a few hours at each star ...
what is the probability they missed something? I'd bet instead that their
certainty of "no one there" for those stars they have searched (to say
nothing of those billions and billions of other stars in the Galaxy) is low
to very low. Same for seti@home. Same for project META and Project BETA. I
hope that these scientists someday get down to the nitty gritty and figure
out what the real odds of detection are ....

Heck, I'll be dead in 20 years! :-) ... can't wait too much longer! :-) ...
all I can do is beat the bushes hoping that someone wakes up soon :-)

You're sort of right though. There doesn't appear to be really big
techological civilizations out there --- nothing really obvious ... it does
seem quiet out there. What I'd like to know though, clearly, is that due to
the fact that the probability of detection is so very very poor or is it due
to the fact that there _really_ isn't anyone out there. How can one model
this so that one can begin to understand? If I was at Mars for example and
looked back at Earth and did a spectrum analysis for say days (a week or two
perhaps) what would I see from Earth in terms of electromagnetic energy?
What do we look like? What's Earth's EM signature like? Once we know this,
then how far away could we detect Earth given some fixed resources (antenna
size, etc. ...)?

And beacons are also hard to find.

Yes ..

At least around 1.42 GHz. But we do not produce super-loud microwave
signals,

Arecibo does ...
Maybe others too ...

and we also don't have a beacon round 1.42 GHz. So why would ET have that
?

There have been a few Russian transmissions of signals to specific stars (or
areas in space say) ...

Maybe it is time to focus on applications that ET really could use, and
then
figure out how the signals of these applications would sound like here,
and where
we could find them in the spectrum.

If in the end it turns out that we would need to build a $100B device to
detect
(with some certainty) a civilisation of our own level within a 1000LY
range from earth,
but it would only take $10B to build a device which can detect (with some
certainty)
oxygen on planets in a 1000LY range, then I'd put my money in the oxygen
detector first...)

Sounds reasonable doesn't it. SETI is on the fringe ...

Now we've come full-circle on the science and funding aspects of SETI.

In article ,
Rob Dekker wrote:

I'm sure there are some radar systems which indeed transmit in this 40GW EIRP range.

40GW EIRP for Parkes would have to be in 0.1Hz, or so, bandwidth. Most
radars will have 100kHz of bandwidth, and might therefore need 1,000
times the power.

Arecibo will easily be able to do that, but only points at a fixed point in the sky
twice a year or so. Not much repetition for any ET that is listening.

Even if it were fixed, it would point to the same place once every
sideral day.

However, it is not fixed; it is steerable to about 20 degrees below
the azimuth in all directions - this is done by moving the feed point.

We need a radar expert to give us some better idea of trade-offs of
what kind of signal we could expect to hear from what kind of application.

I'm not an expert, but the most powerful radar with simple signals
are, probably, the weather radars which are, I think, given as one of the
examples in the FAQ.

High power military radars will use pseudo-random coding, probably
phase modulated, with chipping rates upwards of 100kHz, so will be
completely rejected by S@H as having a flat spectrum in the 10kHz
analyzed, and will have fairly low power spectral densities. They
will be indistinguishable from natural sources.

Arecibo is pseudo-randomly phase modulated about half the time, but
at lower chipping rates, but is also pure CW for about half the
time, when transmitting.

We know from previous SETI's (project Phoenix etc) that there are no obvious,
super-loud microwave signals out there. And beacons are also hard to find.

I think you are assuming that anyone thought that detection was likely.

Maybe it is time to focus on applications that ET really could use, and then
figure out how the signals of these applications would sound like here, and where

I believe that, by doing targetted observations, using long averaging
times, it is practicable to detect leaked analogue TV carriers (unfortunately
analogue TV is going out of fashion after less than a century, here).


If in the end it turns out that we would need to build a $100B device to detect
(with some certainty) a civilisation of our own level within a 1000LY range from earth,
but it would only take $10B to build a device which can detect (with some certainty)

Neither of those budgets is realistic. You are talking of budgets in the
low millions.

PS Please trim the quoting. I have ignored most of this thread because
the articles exceed a quite liberal size limit designed to catch binary
posting and incompetent posters.

In article ,
Rob Dekker wrote:

I'm sure there are some radar systems which indeed transmit in this 40GW EIRP range.

40GW EIRP for Parkes would have to be in 0.1Hz, or so, bandwidth. Most
radars will have 100kHz of bandwidth, and might therefore need 1,000
times the power.

Arecibo will easily be able to do that, but only points at a fixed point in the sky
twice a year or so. Not much repetition for any ET that is listening.

Even if it were fixed, it would point to the same place once every
sideral day.

However, it is not fixed; it is steerable to about 20 degrees below
the azimuth in all directions - this is done by moving the feed point.

We need a radar expert to give us some better idea of trade-offs of
what kind of signal we could expect to hear from what kind of application.

I'm not an expert, but the most powerful radar with simple signals
are, probably, the weather radars which are, I think, given as one of the
examples in the FAQ.

High power military radars will use pseudo-random coding, probably
phase modulated, with chipping rates upwards of 100kHz, so will be
completely rejected by S@H as having a flat spectrum in the 10kHz
analyzed, and will have fairly low power spectral densities. They
will be indistinguishable from natural sources.

Arecibo is pseudo-randomly phase modulated about half the time, but
at lower chipping rates, but is also pure CW for about half the
time, when transmitting.

We know from previous SETI's (project Phoenix etc) that there are no obvious,
super-loud microwave signals out there. And beacons are also hard to find.

I think you are assuming that anyone thought that detection was likely.

Maybe it is time to focus on applications that ET really could use, and then
figure out how the signals of these applications would sound like here, and where

I believe that, by doing targetted observations, using long averaging
times, it is practicable to detect leaked analogue TV carriers (unfortunately
analogue TV is going out of fashion after less than a century, here).


If in the end it turns out that we would need to build a $100B device to detect
(with some certainty) a civilisation of our own level within a 1000LY range from earth,
but it would only take $10B to build a device which can detect (with some certainty)

Neither of those budgets is realistic. You are talking of budgets in the
low millions.

PS Please trim the quoting. I have ignored most of this thread because
the articles exceed a quite liberal size limit designed to catch binary
posting and incompetent posters.

In article ,
David Woolley wrote:
In article ,
Rob Dekker wrote:

I'm sure there are some radar systems which indeed transmit in this
40GW EIRP range.

40GW EIRP for Parkes would have to be in 0.1Hz, or so, bandwidth. Most
radars will have 100kHz of bandwidth, and might therefore need 1,000
times the power.

I did a search for "most powerful radar" yesterday; about 80% of the
hits were TV stations advertising their doppler weather radars. The
most powerful of those I found listed was a 350MW.

[ ... ]
We need a radar expert to give us some better idea of trade-offs of
what kind of signal we could expect to hear from what kind of application.

I'm not an expert, but the most powerful radar with simple signals
are, probably, the weather radars which are, I think, given as one of the
examples in the FAQ.
[ ... ]

The WSR88D (aka NEXRAD) information page claims they are the most
powerful radar--at 680MW.

Didn't find any significant references to military radars, but from
what I've heard, most of them aren't real high power--100KW or so for
things like search and tracking radars. I used to know someone who
worked on the big DEW line radars, and I think he mentioned they were
1.2MW or thereabouts.

I'd never heard of gigawatt radars before doing a search, but there do
appear to be a few that do sub-10ns pulses around 2-20GW. Not sure I'd
want to be near it when it operated, though.

Generating 1GW continuous would likely be a _huge_ task and suck most
of the earths' power generation capacity.


Gary

--
Gary Heston

Contrary to popular opinion, _not_ everyone loves Raymond.