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Re: NOAA warning for rf communications

  • From: Anton L. Kapela
  • Date: Fri Oct 24 14:01:43 2003

Rodney Joffe said:

[snip]

> 900 mhz and 1800 mhz. And facing East or West. And Satellite,
> somewhat above 2.0 ghz.

Hmm.

> And a significant number of ISPs are currently employing 802.11 2.4
> and 5.0+ ghz equipment for last mile links (Proxim Tsunami) and
> Motorola Canopy gear.

The PSD of the modulation (BPSK) that Canopy employs is rather, shall
we say, insane when contrasted with CCK or QAM. I'd be impressed to
find a system that experiences errors or goes off-line completely due
to a CME.

Interestingly, I found a few papers discussing the nature (as well as
proposed detection methods, with examples) of the RF signature of a
CME. The two most easily understood (imho) would be the following:

-http://cdaw.gsfc.nasa.gov/news/cannibalism.pdf

"Long-wavelength radio emission in the decameter-hectometric
(DH) wavelengths (21�280 m or 1�14 MHz in frequency) has
proven to be an important diagnostic for understanding very
energetic coronal mass ejections (CMEs) propagating into the
outer corona and interplanetary (IP) medium (Kaiser et al. 1998;
Gopalswamy et al. 1999; Reiner & Kaiser 1999)."

-http://cdaw.gsfc.nasa.gov/publications/gopal2003.cospar.pdf

Page three of this paper has an excellent time/spectrum graph of
several type II and type III CME (radio) bursts:


Again, these researchers are looking at RF spectrum below 10Mhz. One
could maybe reason (or argue) that the onset of the type III events
(which appear to be initially identified by very broad spectral
content) contain components out to (or above) UHF frequency ranges.
However, after looking over these two papers, I don't see that there's
anything "interesting" above 10mhz, let alone 3 GHz+.

If anyone could offer up evidence that has linked path "fading" or
"desensitization" (of an operator's equipment) to a type II or III
CME, _and_ is operating above 3 GHz, I'm all eyes.

--Tk