In sci.astro.amateur gwatts wrote:

Radium wrote:
Hi:

What is the highest radio frequency used for radio astronomy?

According to the link below, it is 3438 GHz:

http://books.nap.edu/openbook.php?re...=11719&page=11

Is 3438 GHz the highest radio frequency used for radio astronomy?

If you read on a little farther you'll find
'blurring the distinction between radio astronomy and infrared astronomy.'

So where do you want to draw the line between radio astronomy and
infrared astronomy? There's you're answer.

Hi, Radium, gwatts, and all.

I'd agree that the real question here may be where to draw the line
between radio and infrared, and thus between radio astronomy and
infrared astronomy.

What I learned about 40 years ago was that while the line wasn't
a clear one, the shortest or highest-frequency range of radio waves
traditionally placed in that classification were "millimeter waves"
with a wavelength of 1-10mm. Given that the speed of light, c, is
very close to 3 x 10^10 centimeters per second, so that a 1 cm or
10mm wave would have a frequency of around 30 Gz, this category
(also known as Extremely High Frequency or EHF) has a 30-300GHz
range.

A frequency of 3438 GHz, with a wavelength a bit shorter than
100 microns, would thus be about an order of magnitude higher
in frequency than the top of the EHF range. While I'm not sure
if there's a specific technical name for this range (analogous
to the various categories of radio waves like EHF), my first
layperson's guess would be that it could be considered very
far infrared (that is, far from the visual spectrum and close
to radio).

It's interesting question how radio and infrared astronomy are
distinguished: mainly by the nature of the waves, or also by
the apparatus used. I'd like to to learn more of this myself.

Again, I'd emphasize that in giving the range for EHF, I'm not
saying that anything above 300 GHz wouldn't be considered radio,
only mentioning this category as an example of what was
traditionally considered near the top of the radio spectrum.

Maybe Laura or others could comment more expertly on this.

Most appreciatively,

Margo Schulter

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