"David Woolley" skrev


In article ,
"a servant of Isa, Yeshua John15.13@Heaven" (bogus address) wrote:

[ sci.astro.seti added, as that is a more appropriate newsgroup for a
posting with a science content. ]

Subject: Request to SETI - Was: Thank You From SETI

You are addressing this to the wrong place, as there is no such
organisation as SETI (SETI is a process done by many organisations)
and Berkeley Space Sciences don't often read these newsgroups (they are
more likely to read sci.astro.seti, but even then don't often contribute).

I don't understand Your DATA i file *work_unit.sah*

You are not particularly supposed to, although they havn't taken any
steps to obfuscate it. They don't want people doing their own
analysis and either making a mistake in the analysis process and making
false claims of a detection, or even making a real detection and
getting to the press before them (the former being much more likely).

However, the parameter part is fairly obvious and the uuencode type level
of the encoding can easily be stripped. It is clear from the parameters
that the data is a sequence of complex numbers containing only the sign
bit for each of the real and imaginary parts; that part can easily be
resolved by a few experiments to determine the sequence of the data and
how it is interleaved. There is one other subtlety in that the splitting
calculations roll the spectrum, but people have solved that one as well
by trying test data.

and therefore I have NO chance to compare with own downloads from the
Univers (I have NOT make them yet, but I wish to do it)

S@H 1 work units are only suitable for antennas with the same beam width
as Arecibo, although BOINC provides additional parameters to remove
that restriction. A lot of the frequency resolution will be wasted as
well, as the frequency stability of amateur equipment is one to two
orders of magnitude worse than that for which S@H is optimised; that will
mean that an awful lot of time will be wasted processing 128K FFTs on
data that might only support 4K FFTs, unless you completely fake the
time scales of the data, in which case you will end up wasting
time processing chirp rates that are unreasonably large, will not be
using the full beamwidth in drift scan mode and will require a much
larger receiver bandwidth.

In the FUTURE people on Earth will understand, that it is important, we
use

The SETI League has been doing this for the best part of a decade
(http://www.setileague.org). Note that there are still very few active
stations and that is with a lower technical specification than you
are assuming.

a lot of small radio-telescopes, so that we can focus on many objects on
the

Focussing on many objects at the same can also be done using relatively
compact phased arrays, e.g. the Allen telescope.

sky at the same time and for a long periode (more than a week, I think).

That requires steerable antennas. Most people doing amateur SETI can
only afford, or only live with the neighbours, by using fixed antennas.

Because you have to do non-coherent averaging of the signal
above about 10 seconds, with a stable receiver and more like above 0.1s,
with an amateur system, and taking into account the relative sizes of the
antennas, you will need to observe for over a day to match 13 seconds
of Arecibo time. That means that the first order chirp (second order
Doppler) corrections in the client will be totally inadequate.

In fact, it works out that small antenna SETI is best for short duration
signals, as long duration signals will stay around to be found by the
much more sensitive large antennas. The real advantage of small antennas
is that a small number of them can, together, simultaneously cover the
whole sky, alowing the detection of short duration signals.

Here in Denmark we can NOT see around the Center of our Galaxy, ...

Note that there is a European Radio Astronomy Society (ERAC).

more stars, MORE (hypothetic) Life-2.

Using large dishes is the way to get more stars. The range scales with
diameter and volume with the cube, meaning n times diameter allows you
to search n^3 stars.

Especially for small dishes, the range limits mean that there is unlikely
to be much benefit in aiming within the galactic plane. Any contact
which is far enough out for spherical symmettry to have broken down will
have a very long round trip time. Most of the benefit that is associated
with the galactic centre would apply to any direction in the galactic
plane, but even straight out of the plane takes you to over 1000 years
round trip time.

Group 1 can watch frequency 1,42000 GHz.
Group 2 can watch frequency 1,42001 GHz

In practice, some people will have receivers that have much wider pass
bands.

On the other hand, there is no evidence that large enough numbers of
people
are interested to be able to form multiple groups.

("Hello"-signal time-interval perhaps every 2 weeks)

Small dish SETI is only likely to produce comparable detection rates to
big dish SETI (approximately zero in 20 years).

Arecibo:
305m - 73.062 m^2

The effective diameter is rather less (about 100m for the line feed on
the carriage house and up to 200m for the Gregorian).

Antenna signal-minimum:
1*10^-23 Watt / m^2 * 73.062 m^2 = 7,3*10^19 Watt

Depends on detection thresholds and integration time. Your estimate
is rather pessimistic. See below.

Little-Radio-reflector:
2m - 3,14 m^2

Typical amateur SETI is 3 or 4m, ex C-Band TVRO (in the USA). ERAC claims
to be able to source dishes in Europe.

7,3*10^19 Watt / 3,14 m^2 = 2,3*10^19 Watt/m^2

This is a rather round about way of doing things. The threshold power,
as described in the FAQ, is kT per Hertz, where the bandwidth for Arecibo
is about 100 times better than a typical amateur system, and the system
noise
is likely to be less as well. The SERENDIP system has an overall T of
about 45K. About 12K of this is extrasterrestial, so irreducible.

You can't use this as the actual threshold, but must multiply it by a
factor
to produce an acceptable false positive rate. That's 8 for Phoenix and 22
for S@H; S@H is larger because of the large number of different parameters
it tries.

k is 1.38066...E-23 J/K.

So the noise is about 3E-23 W in 0.05Hz. Using an 8 times threshold
(basically assumes signal is source chirp compensated) it's about 2.4E-22.

Multiplying by the capture area and using a SERENDIP type 100m radius,
gives about 3E-26 W/m^2 in 0.05Hz.

Such kind of antenna, You use, must be very expensive!

A cheap one (around 200 US $) - how good is it ?
(1*10^10 Watt ?)

The antenna won't make much difference, once you have a big enough
area (1m is probably too small for 1.4GHz as it's only five wavelengths
across). What matters is the low noise amplifier, which should be around
US$100 to get well within an order of magnitude of the Arecibo figure,
and the stability of the receiver, and most people seem to assume 10Hz
in the short term. Being pessimistic on the noise, the threshold power
will be about 400 times worse, so 1E-19 W in 10 Hz.

You'll need to under illuminate the dish, to avoid looking at the hot
ground, so maybe use 0.5 * pi. That gives about 6E-20 W/m^2 in 10 Hz.

Can a little radio-telescope be inable to get contact with big-signals ?
(like 1*10^10 Watt ?)

If you are talking about effective isotropic power (EIRP) that is not
big in a SETI context. Arecibo can do over 1E13 Watts. However, the
answer is that you are many orders of magnitude below the 10 second
integration detection threshold, even from the nearest star, at that
level. If you go to a four metre dish, get the receiver stable to
1 Hz, and average over 200 seconds, you begin to achieve a few 10s of
light year range (see the FAQ for details).

If it can, I find it important, that You create a program we all can
understand and use together to synchronization our positions.

Who is you. Berkeley SSL are probably not even reading the thread, and
they have no mandate to fund your research. There are a number of
pieces of software, e.g. SETI-Fox, for processing amateur SETI inputs,
available on the web.

The servant of Michael

Drop this and your From line name, as they devalue your contribution.

PS. You have a broken newsreader. You have posted this as a followup,
but it doesn't have a References header.

PPS. I hope all the arithmetic is right!


Thank you for your responce.

I'm very bad in english (I'm danish), so it will take me a long time to
understand, what you have been written.

I will be back :-)

-

Another thing:

Are you in able to crack the code, se ...

2233
english version ...
2305

(You can win around 140 US $, if You are the first one)


With kind regards,
Mogens Kall
The servant of Michael

File-number:
2338