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[Ham-80211] OT??? High power 2.4 GHz rules change

David Young dyoung at pobox.com
Thu May 18 07:10:31 UTC 2006


On Wed, May 17, 2006 at 01:53:14PM -0400, Jeff King wrote:
> Nope, 2.4ghz will not go the way of 220mhz. Both the HAMS and the WISPS seem to be forgetting something. Both Part 15 AND Part 97 are secondary users here. Part 18 is the primary user, things such as microwave ovens and industrial equipment running into the kilowatts with no requirement for APC. 
> 
> The WISP's need to spend their time fighting for protected spectrum
> as they will never get the ISM industry to vacate 2.4ghz. If they feel
> they serve the public so much better then amateur's do, I suggest they
> go after the 420-450mhz band, which is unused over the majority of the
> country. This offers excellent foliage penetration and by displacing
> the hams they would have a range of frequencies they could actually
> build a long term business model on.

Assorted thoughts:

I get a little itchy when I hear "protected spectrum," because it brings
to mind businesses that monopolize broadband access simply because
their access to customers---by air, wire, whatever---is "protected,"
not because they prevail in a melee of high-tech innovation.

I am skeptical that a WISP can build a long-term business model on a
mere 30 MHz of spectrum, especially if it anticipates demand for higher
and higher bandwidth and/or competition from wire & fiber.

It seems to me that foliage penetration at 400 MHz is a double-edged
sword, especially if all you have is a slim slice of spectrum: it can
really cut down on spatial re-use, even within one operator's network.
It can help to have a "backstop" for your radio emissions.

As a WISP moves to lower and lower frequencies (I read about 900 MHz,
700 MHz, 400 MHz, ...), it needs a bigger and bigger antenna to get the
same amount of gain over noise and interference.  A WISP can only make its
CPE so big.  At some point, an operator's gains from foliage/buildings
penetration may be overwhelmed by the losses due to a less selective
antenna, fewer channels, and narrower channel width.  I have a hunch
that the losses will overwhelm the gains at a frequency much nearer 2.4
GHz than, say, 400 MHz, especially as techniques like beamforming and
MIMO enter the picture.  It's just a hunch.

Dave

-- 
David Young             OJC Technologies
dyoung at ojctech.com      Urbana, IL * (217) 278-3933




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