wrote in message
...
In rec.radio.amateur.antenna Radium wrote:
On Jul 13, 4:55 pm, wrote in
http://groups.google.com/group/sci.a...e3e8f5e?hl=en&
:

In rec.radio.amateur.space Radium wrote:

Okay. But what if this is a supercooled AM radio receiver on a
spaceship orbiting Earth? If I am on a space station like MIR and
this
station has a supercooled AM radio 44.1 KHz frequency receiver, will
I
hear anything specific of magnetars?

Generally, super cooled electronic components stop working.

Isn't a super cooled receiver less vulnerable to thermal noise than a
receiver of a higher temperature? This is why SETI super-cools their
radio receivers. So that the heat will not generate electric currents
that would drown-out the intended signals in hiss.

44.1 KHz is the carrier-frequency this hypothetical receiver
receives.

A super stupid frequency to pick. Generally for listening for natural
phenomena, you want a wide as possible bandwidth given the noise
floor.

But humans only hear from 20 to 20,000 Hz. So why use a higher
frequency?

From what you think, what is the best frequency for listening to
magnetars and other natural phenomena?

I place the frequency of this hypothetical AM radio carrier wave at
44.1 KHz for the same reason CDs use a sample rate of 44.1 KHz -- it
is the minimum required to prevent aliasing.

An AM receiver isn't digitizing anything, sample rates don't apply,
and aliasing doesn't apply.

Isn't it true that the carrier-frequency must be at least 2x the
highest intended frequency of the modulator signal?

I am not talking about sample rates. I am talking about carrier
frequency. From the answers to my previous questions regarding carrier
frequencies, I thought it was established that you mathematically
can't have a modulator frequency more than 0.5x the carrier-frequency.
What happened?

Since humans hear up to 20 KHz it is mathematically-required that the
carrier frequency be at least 40 KHz or 2 x 20 KHz. Due to physical
factors it would be most practical to use a carrier frequency slightly
higher than 2x the maximum intended modulator frequency -- hence 44.1
KHz.

If you had the slightest bit of education or common sense, you would
be asking a question that makes sense instead of going on forever
about the minutiae of what makes your questions idiotic.

Here's a question that makes sense:

Are there any sources of RF energy outside our solar system that
could possiblely be detected given an environment free of the
constraints of the ionsphere and man made noise?

If so, what frequecy or frequencies would they be seen at and what
would be the general characteristics of such a signal?

Also, the same question but operating from the Earth's surface.

And this is an astronomy/astro-physics question, not an electromagnetics
question.

Notice there is nothing in there about "supercooling", modulation
type, sampling rates, or any of the other nonsense in your question.

Babbling twit.


--
Jim Pennino

Remove .spam.sux to reply.
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Perhaps archimedes plutonium has changed his name. Sounds about the same-
ploughing on and on without any idea of what he is doing -no answer will
shut him up. Possibly that is the right approach-killfile.

--

Don Kelly
remove the X to answer
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