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Re: S band and Eagle: an appeal for ahigherleveldiscussion



Hi John,

My concern on the uplink side is that any individual interferer is low power 
but there will be many tens of thousands of them wihin the field of view of 
the satellite.  If there are enough of them on the ground to be a problem in 
the immediate vicinity of a station, then surely they would be a problem for 
the satellite looking down.  I agree that we can probably scream louder than 
the collective noise, but how we get the signal to scream that loud is 
another question.  Someone pointed out that power amps are going to be cheap 
because of all the WiFi gear out there, and that's probably true, but we're 
not going to get to a kw EIRP from one without a pretty big antenna (1W to 
1KW is 30 db, right?).  And, there aren't any up-converters coming free like 
we had with the MMDS downconverters that we all found.  We have ready access 
to equipment and power on 2m and 70cm, making U and V uplinks easy and wide 
spread.

On the downlink side, my own opinion is that there will be a natural 
saturation point of 2.4 ghz equipment that is below the projections.  One of 
the reasons I have for this opinion is that self-interference and marketing 
will drive many to 5 ghz (we see cordless phones already packing up and 
headed there now), and the demands on WiFi will force the move to 5 ghz for 
its non-overlaping channels.  802.11a is already there, and 802.11n is 
coming (pre-n stuff is on 2.4, but the standard also covers 5 ghz).  One 
cranked-up 802.11n channel covers 40 mhz, which pretty much wipes out half 
of the 2.4 ghz allocation, so it's not going to live long down there.

The other factor is that there is a limit to how many gizmos we will put up 
with.  The manufacturers have this happy stockholder-driven picture of 
everyone wandering around with a thingy sticking out of their ear, 
bluetoothed to a thingy on their belt, which talks to another thingy on 
their belt, in their pocket, on their wrist, the car naviation system, the 
home entertainment system, keyboard, mouse, coffee maker, and so on, ad 
nausium (with emphasis on the nausium part).  My prediction is that there 
will be a revolt at some point, with too many gadgets being thrown at us, 
and people will buy ONE device that has a bunch of these things all built in 
(without the many wireless links).  Either that, or our attention deficient 
society will tire of this line of business, and the rest of the gadgets will 
sit turned off in the drawer, on the shelf, or in the land fill, awaiting 
the day when some future archaeologist digs them up and wonders what on 
Earth we were thinking.  The area networks, replacing the ill-fated BPL 
systems, will be on licensed spectrum, because (as my own internet service 
provider is finding out) unlicensed spectrum is too crowded to build a 
business around.  All of this adds up to much less 2.4 ghz interference.

Just my own opinion,

Greg  KO6TH


----Original Message Follows----
From: "John B. Stephensen" <kd6ozh@comcast.net>
To: "i8cvs" <domenico.i8cvs@tin.it>,"Greg D." 
<ko6th_greg@hotmail.com>,"AMSAT-BB" <amsat-bb@amsat.org>
Subject: Re: [amsat-bb] Re: S band and Eagle: an appeal for a 
higherleveldiscussion
Date: Mon, 11 Sep 2006 03:20:05 -0000

For 13 cm uplinks we can just overpower the interferers. The WiFi
interference is attenuated at the same rate as the uplink signal. Most
interferers are 10 mW EIRP or less and the uplink is 1 KW EIRP or more.

For a 13 cm downlink, increasing the power level is impractical as solar
panels are very expensive.

73,

John
KD6OZH

----- Original Message -----
From: "i8cvs" <domenico.i8cvs@tin.it>
To: "Greg D." <ko6th_greg@hotmail.com>; "AMSAT-BB" <amsat-bb@amsat.org>
Sent: Monday, September 11, 2006 02:11 UTC
Subject: [amsat-bb] Re: S band and Eagle: an appeal for a
higherleveldiscussion


 > ----- Original Message -----
 > From: "Greg D." <ko6th_greg@hotmail.com>
 > To: <amsat-bb@amsat.org>
 > Sent: Sunday, September 10, 2006 8:40 PM
 > Subject: [amsat-bb] Re: S band and Eagle: an appeal for a higher
 > leveldiscussion
 >
 > > If 2.4 ghz pollution is going to be a problem for stations on the 
ground
 > who
 > > are looking up (and away from) the noise, how is it possible that a
 > > satellite in the sky looking down on half of a planet's worth of 2.4 
ghz
 > > noise, is going to be able to pick out one earthly station over the 
din?
 > > This is totally backwards in my mind.
 >
 > > Greg  KO6TH
 >
 > Hi Greg, KO6TH
 >
 > It is possible !
 >
 > During the test of 23 Feb 2003 AO40 was looking down on half of the
 > planet's using his S1 high-gain dish connected to the S1 RX worth of
 > noise on 2400.475 MHz and was able to pick out G3WDG and i8CVS for
 > the first experiment on S/K band in wich an amateur satellite was
 > succesfully tested the first time to receive over the dim an uplink at
 > 2400.475 MHz
 >
 > So it is totally backward in my mind why the S band is considered a sewer
 > three years now from the above test.
 >
 > If you look at the following page you have the complete report written by
 > G3WDG and a wave-file showing how clean where both signals over the
 > noise on SSB
 >
 > http://www.g3wdg.free-online.co.uk/s_ktest.htm
 >
 > 
--------------------------------------------------------------------------
--
 >
 > Quoting Stacey E. Mills W3SM
 > [amsat-bb] AO-40 Update, 2003-02-23
 >
 > Two tests were performed on AO-40 today.
 >
 > The second test involving the S-band receivers was completely
 > successful.  Extremely strong downlink signals were possible using S-band
 > uplink to K-band downlink.   Charlie (G3WDG) phoned me and I heard
 > beautiful downlink signals from his ~5 watt uplink to S1.  S2 was also
 > active, but because of its higher, less common frequency (2446 MHz), it
may
 > not have been tested.  The S1 Rx uses the S1 Tx high-gain dish, and the 
S2
 > Rx uses the 5 turn helix used by the S2 Tx, so signals would not be as
 > strong through S2 at low squint.  More information will undoubtedly be
 > posted on this by the participants, but special thanks to Charlie 
(G3WDG),
 > Mike (N1JEZ),  and Dom (I8CVS), and any others who participated in this
 > successful test.
 >
 > The S1 Rx can certainly be listed as fully functional.  We will await
 > further testing/info. on the S2 Rx.
 >
 > --W4SM for the AO-40 Command Team
 > 
--------------------------------------------------------------------------
--
 >
 > Quoting Charlie G3WDG
 > [amsat-bb] AO-40 S/K Test
 >
 > All,
 >
 > I have posted some info on the tests here, including some recordings of
 > G3WDG and I8CVS's S-Band signals received on K-Band.
 >
 > http://www.g3wdg.free-online.co.uk/s_ktest.htm
 >
 > 73
 >
 > Charlie G3WDG
 > 
--------------------------------------------------------------------------
--
 >
 > Best 73" de
 >
 > i8CVS Domenico
 >
 >
 >
 > _______________________________________________
 > Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author.
 > Not an AMSAT-NA member? Join now to support the amateur satellite 
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