Does it still amaze you that radio works?

Thread Starter

KL7AJ

Joined Nov 4, 2008
2,224
An S-9 H.F. signal arriving at the input terminals of a shortwave receiver has on the order of 25 PICOWATTS of power. Down at the noise threshold, the signal is on the order of a few dozen FEMTOWATTS.

After half a century I am still intrigued by the fact that you can slosh a few electrons up and down a coat hanger and be heard thousands of miles away. If this still doesn't amaze you, you have no soul.

Eric
 

MaxHeadRoom

Joined Jul 18, 2013
19,677
Another amazing feat is the capability of a Satellite station that can keep in sync with my Dish!.
On the other end of the spectrum was Rugby Radio, conceived in 1910 to transmit to anywhere in the British Empire and later to communicate with a submarine a couple of fathoms anywhere under water.
The normal working voltage of the aerial was 165,000 volts r.m.s. and the current at the base of the aerial was about 750 amps. The earth system consisted of an open network containing about 120 miles of copper wire buried a few inches in the ground and occupying a space of 1600 feet wide under the length of the aerial.:cool:
Max.
 

GopherT

Joined Nov 23, 2012
8,012
An S-9 H.F. signal arriving at the input terminals of a shortwave receiver has on the order of 25 PICOWATTS of power. Down at the noise threshold, the signal is on the order of a few dozen FEMTOWATTS.

After half a century I am still intrigued by the fact that you can slosh a few electrons up and down a coat hanger and be heard thousands of miles away. If this still doesn't amaze you, you have no soul.

Eric

Could you calculate the wattage of the signal coming from the Rosetta spaceship flying next to the comet for the past 13 months.

http://www.space.com/27697-rosetta-comet-landing-full-coverage.html
 

nsaspook

Joined Aug 27, 2009
6,704
http://blogs.esa.int/rosetta/2014/08/05/tracking-the-spacecraft-following-a-comet/
Yes; taking ESA’s New Norcia 35m station as a reference, and thanks to its 1000m2 antenna collecting surface and gain of 68.3dBi, Rosetta’s weak signal is captured and results in a received power of -157.38dBW or 1.83E-16W. This is still very small – just 1.83 femptowatts. The use of cryo-cooled low noise amplifiers working at -260oC allow the detection of such signals.
What amazes me is not radio but how our radio signals are so distinctly human in their nature that we can resolve them from naturally generated signals at levels below the noise level. Our signals are differ from most natural signals by being neither random or regular. The generation of deterministic signals with changing patterns is the sign of intelligent communication. When we want to hide our radio signals we mimic nature with deterministic randomness that looks like noise unless you have the key, So maybe what we think is space radio noise is intelligent communication between beings, we just lack the proper key to decode it.
 
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BR-549

Joined Sep 22, 2013
4,938
That's find for secure signals, but what about a beacon. How do you get someones attention?

You broadcast on an unnatural frequency. Right smack dab between the 1st and 2nd energy levels of the H atom. Any intelligent life will investigate that.

However I would not recommend it. Even though I don't believe in alien life, I could be wrong.

Life is predatory.
 

Thread Starter

KL7AJ

Joined Nov 4, 2008
2,224
http://blogs.esa.int/rosetta/2014/08/05/tracking-the-spacecraft-following-a-comet/


What amazes me is not radio but how our radio signals are so distinctly human in their nature that we can resolve them from naturally generated signals at levels below the noise level. Our signals are differ from most natural signals by being neither random or regular. The generation of deterministic signals with changing patterns is the sign of intelligent communication. When we want to hide our radio signals we mimic nature with deterministic randomness that looks like noise unless you have the key, So maybe what we think is space radio noise is intelligent communication between beings, we just lack the proper key to decode it.
I LOVE your term "deterministic randomness." I've always asserted that what we call noise is only "random" because we don't have the processing power to decode all the wave parameters at once...such as phase, direction of travel, polarization, etc. Nature abhors random.
 

atferrari

Joined Jan 6, 2004
3,627
I still measure wavelength in cubits. :) (MY cubit happens to be exactly half a meter, which is quite convenient for paying out dipole wires. :) )
It is measured with the middle finger extended?

I know that in a pinch I can estimate measurements using de distance between my thumb and little finger with my hand open and flat (gives between 21 and 22 cm).
 

nsaspook

Joined Aug 27, 2009
6,704
I LOVE your term "deterministic randomness." I've always asserted that what we call noise is only "random" because we don't have the processing power to decode all the wave parameters at once...such as phase, direction of travel, polarization, etc. Nature abhors random.
We are limited in our of 'decoding' of random noise sources by two operational factors that constrain us.
1. No FTL communication in signal locality. The measurements we take are constrained by time to the past not present. In practical systems this limits our resolution.
2. Predictability of outcomes. The assumption that one can predict the outcomes of all possible measurements. In practical systems this limits our accuracy.

These limit the classical computability of determinism at some scale. We can only measure to see probabilities, not the exact nature of the source function. If it is impossible to signal faster than light then it is impossible to predict the outcomes of all experiments even if there is some underlying hidden model causing randomness that is deterministic. So for us nature is random (the uncertainty principle/perfect predictability) at the quantum scale.

Perfect predictability is the one nut we can't crack.
 
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djsfantasi

Joined Apr 11, 2010
5,913
It is measured with the middle finger extended?

I know that in a pinch I can estimate measurements using de distance between my thumb and little finger with my hand open and flat (gives between 21 and 22 cm).
After converting to metric, my finger span is between 22 and 23cm (9"). My stride is 5 feet. A US Dollar bill is 6" long...
 

djsfantasi

Joined Apr 11, 2010
5,913
even if there is some underlying hidden model causing randomness that is deterministic. So for us nature is random (the uncertainty principle/perfect predictability
Are you familiar with cellular automata theory. There are systems defined by simple rules, that produce randomness. See Wolfram and Rule 30. So underlying models can produce randomness.
 

nsaspook

Joined Aug 27, 2009
6,704
Are you familiar with cellular automata theory. There are systems defined by simple rules, that produce randomness. See Wolfram and Rule 30. So underlying models can produce randomness.
I'm not saying physical models can't be random or look random at the limits of our technology. I'm saying there are limits to our ability to compute (reversibility) true randomness or even Chaos at some scale. Rule 30 is described as chaotic so small changes in the initial conditions can create events that look random due to our inability to perfectly predict outcomes.
 

djsfantasi

Joined Apr 11, 2010
5,913
I did not mean to imply that you believed models could not be random or look random. I was just presenting cellular automata theory (CAT) as an example of a model that produced randomness. As you mentioned and I agree, there are limits to our ability to compute true randomness or even understand random events. Supposedly, a good source of randomness is atmospheric noise. See http://random.org/
 

nsaspook

Joined Aug 27, 2009
6,704
I did not mean to imply that you believed models could not be random or look random. I was just presenting cellular automata theory (CAT) as an example of a model that produced randomness. As you mentioned and I agree, there are limits to our ability to compute true randomness or even understand random events. Supposedly, a good source of randomness is atmospheric noise. See http://random.org/
Sure, cellular automata theory is one method of many to generate a 'Pseudorandom' number in a computer. Some are cryptographically secure and can be used to secure radio and communications in general. The streams generated from cellular automata methods like rule 30 (as a PRNG function) are not as there is a correlation and fault attack to reverse the Stream Cipher and recover the secret initial conditions.
http://mathworld.wolfram.com/RandomNumber.html
 
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