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.