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Re: S band and Eagle: an appeal for ahigherleveldiscussion



A calculation was made estimating the worst-case contribution of 802.11
equipment in the footprint and it raised the noise floor at the satellite,
but not by much. At S-band, a 2-foot dish gives 26 dBic of gain and with 4
parallel 1 W amplifier ICs ($5 each) this provides 1600 W EIRP. We'd like to
allow use of WiFi parts as most mcrowave power transistors cost over $100
each.

I originally argued for an L-band digital uplink but was persuaded that it's
too risky.

73,

John
KD6OZH

----- Original Message ----- 
From: "Greg D." <ko6th_greg@hotmail.com>
To: <kd6ozh@comcast.net>; <domenico.i8cvs@tin.it>; <amsat-bb@amsat.org>
Sent: Monday, September 11, 2006 05:58 UTC
Subject: Re: [amsat-bb] Re: S band and Eagle: an appeal for a
higherleveldiscussion


> 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.
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>
>

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