Antenna for detecting other civilization


It is a fact that for many years billions of dollars have been spent to try
to locate other civilizations, but without a success.



The method used was using high frequency radio waves using large antenna
dish antennas.



These antennas can communicate with very far spaceships, even at a distance
of 100 AU. But they are not suitable to make contact with other
civilizations because of 2 main reasons:



1.      The antenna is very much directional and receives or transmits
signal only to a very narrow angle in the sky. A 70 db antenna ha an angle
of only 1 part of 10 million of the sky. To detect signal from other
civilization using such antenna would not only require that the antenna will
be aimed exactly at the transmitting antenna of that civilization, but also
that the antenna of that civilization will be aimed exactly at Earth. The
chance that this will occur is 100 e12.

2.      A large dish antenna used today transmits in a narrow bandwidth of
64 KHz using a carrier frequency of 8 GHz. The ratio between the two
frequencies is about 1:100,000. If an antenna from another civilization will
transmit at another frequency out of 100,000 options, than we will not
receive it.



To overcome this I prepared a plan for a different antenna.



The antenna I thought of is a simple dipole antenna in space. This antenna
transmits and receives to all directions and is not limited to a very narrow
frequency.



In order to make it very sensitive to signals I thought to make it as long
as possible.



I found out that the solar storms make noise, and as we distance the sun the
frequency of the noise and the power is decreased.



At frequency of 50 KHz and 1 AU from the sun the noise is not significant.
At 2 AU the frequency is 25 KHz and at 10 AU the frequency we can use is 5
KHz.



The first possible antenna I thought of is a dipole, having a length of 3
Kilometers, placed as a satellite to Earth. To make this antenna and to put
it in space would not cost much and there are no risks.



It will be optimized for a frequency of 50 KHZ, but will also receive
frequencies of 20-200 KHz.



The effective area of the antenna will be 9 square kilometers. This is 100
times more than the largest antenna array on earth.



In order to detect a signal from outer intelligence, there is a need to
detect not more than 100 bits of information.  The time for this can be for
example 1 day or 100,000 second. The bit-rate will be about 0.001 bits per
second. The noise level of an amplifier for that antenna is e-21 watt per
Hz. The noise level for that need is e-24 watt.





The ratio between the communication distance and the transmitted signal in
this case is:



Distance^2            Wavelength^2            36

-----------------    =  -----------------------   =  ------   =~ e26

P transmitter           P receiver                e-24



In the case that the transmitter power is one million watts, the distance is
e16 kilometers, or about e8 AU. This is 1000 times more than the closest
star to us.



If we put the antenna more far from the sun, the temperature drops and than
the antenna wire will have lower electrical resistance. We will be able to
make it longer without increasing the weight. A 6 Kilometer antenna can be
at about 3 AU from the sun and will have the same weight as a 3 Kilometer
antenna.



If we further increase the distance from the sun, were the temperature is
below 77 degrees Kelvin, than we can use superconductors instead of a metal
wire. This will dramatically decrease the weight and enable us to use a 100
Kilometer antenna and frequency of 1.5 KHz that will increase the
sensitivity by 1000. The effective area of that antenna will be 100,000
times the area of the antenna arrays on earth.



At that frequency and distance from the Sun there is almost no noise from
plasma oscillation.





By Gil Teva gilteva@actcom.net.il





(1) http://www.femto.de/datasheet/DLPVA100BUNS.pdf



(2) http://www.ka9q.net/mpf_budget.html



(3) http://farside.ph.utexas.edu/teaching/jk1/lectures/node83.html

 (formula 1001)





(4) http://www-pw.physics.uiowa.edu/plasma-wave/helios/summary/summary.html



(5) http://www.amsuper.com/html/newsEvents/news/105793757741.html