On Fri, 12 Sep 2008 15:22:43 -0700 (PDT), "Green Xenon [Radium]"
wrote:

What would be heard on a 40 Hz AM DX receiver

Very slow morse code. That's about the only form of AM modulation
that will work with such a low carrier frequency.

that uses the most
sensitive type of magnetic loop antenna?

I doubt there would be any
hissing since that artifact would involve high-frequency sounds and a
40 Hz carrier cannot transport modulation-signals higher than 40 Hz
[violation of Nyquist theorem].

Well, if your carrier frequency is 40 Hz, the highest AM modulation
frequency that will work will be 20Hz. That's also approximately the
modulation bandwidth. There are a few young individuals that can hear
down to 10-30Hz, but most people can't. It's a form of hiss, but at a
much lower fequency.

I also don't think power lines would have any perceptible affect on a
40 Hz receiver. In USA, the electric power has a frequency of 60 Hz --
in Europe, its 50 Hz. Since 40 Hz is below these power frequencies, I
doubt they would cause interference on 40 Hz. If I was receiving at or
above the power frequencies, I do think there would be disturbance but
not if below.

Think again. It really depends on your receiver bandwidth. For AM,
it's going to have a fairly wide IF bandwidth in order to work at a
40Hz carrier. Although power line 60Hz will not be directly coupled
into the receiver, there's probably enough gain after the filter to
cause some problems. It's difficult to tell without clues about the
rx gain distribution and antenna configuration.

Would any interferences from outer space be perceptible on a 40 Hz AM
receiver? Galactic noise?

Not outer space. However, there is a substantial amount of
atomospheric noise at low frequencies, mostly from lightning and
atmospheric electricity discharges.
http://en.wikipedia.org/wiki/Atmospheric_noise
That's one reason why it's not useful to build an extremely sensitive
VLF receiver. Whatever you're trying to hear, it literally buried in
atmospheric noise.

Thanks,
Radium

Give up.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558