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Re: Re: xm-1 satellite as test sig



We sure could use a friend down at XM radio about now .... I have been
searching all morning and can't find much info at all about this one, not
even an EIRP footprint map. what I could find is that XM radio paid over $80
million for access to 12.5 MHz. of S band bandwidth in the frequency range
of 2332.5 - 2345 MHz. They intend on dividing this bandwidth into 6
channels. 2 channels of 1.84 MHz. each will be allocated to each satellite,
the remaining two channels will be used for terrestrial repeaters to help
fill in dead spots (like downtown Manhattan). Each channel will transmit a
3.28 MB/S data carrier. It appears they are using COFDM (coded orthogonal
frequency division multiplexing) modulation. This is based on a press
release form one of XM's vendors. The maximum EIRP is 68 dBW at beam center.
The footprint of each satellite is definitely limited to the continental
U.S, as per XM Radio's filings with the SEC.. Most GEO satellites have a
relatively low power, narrow band beacon for sending telemetry. It is
usually at the extreme low or high end of the transponder. I think that
signal would be much more useful to the ham community than the wideband data
carriers.

Howie
AB2S

----- Original Message -----
From: "Greg D." <ko6th_greg@hotmail.com>
To: <amsat-bb@AMSAT.Org>
Sent: Tuesday, July 10, 2001 12:51 PM
Subject: Re: [amsat-bb] Re: xm-1 satellite as test sig


> Hi Wayne,
>
> For background, my setup is based on the Drake 2880 which was modified
> by moving the local oscillator to 2100mhz.  This makes the stock IF
> passband of the Drake (222 to 408 mhz) cover 2322 to 2508 mhz input.
> My IF receiver is an ICOM R7000 wide band all mode scanner, set for
> upper sideband.
>
> I found the satellite signal very broad in frequency; tuning +/- 100's
> khz or more showed a broad peak with a few dips here and there.  I
> forget the exact numbers, but it was clear that tuning wasn't very
> critical.
>
> 73s,
>
> Greg  KO6TH
>
>
>
> >From: Estes Wayne-W10191 <W10191@motorola.com>
> >To: amsat-bb@AMSAT.Org
> >Subject: [amsat-bb] Re: xm-1 satellite as test sig
> >Date: Tue, 10 Jul 2001 10:13:01 -0500
> >
> >Greg KO6TH wrote:
> >
> >I set my Rx for the 2333mhz frequency (no doppler), and begin sweeping
the
> >antenna towards the predicted location.  There's a very definite increase
> >in
> >the noise floor, and this on a system that cannot hear the Sun at all.
> >What
> >is most interesting is listening to the QSB in the noise as the antenna
> >sweeps.
> >I think what I am hearing are the various lobes and sub-lobes in my
receive
> >pattern.  A systematic sweep, looking at the S-meter, should be able to
> >"paint" where the hot spots are.  Either I could use that to aim the
> >antenna, or even better, to look at the pattern and get an idea what's
> >wrong
> >(various aberations, and such).
> >
> >Wayne W9AE replies:
> >
> >Interesting.  I listened for the 2444.54 MHz signal last night at about
> >0400Z and I couldn't detect any change in noise level as I swung the
> >antennas around.  The satellite was well above the nearby trees.  Just to
> >confirm that my receiving system was working, I went to the AO40 S2
middle
> >beacon and could hear it 4 to 5 S-units above the noise (MA ~30).
> >
> >I guess I can try listening for the 2333.54 MHz signal.  With a 2278 MHz
> >L.O. on my downconverter, I should be able to hear it at 55.54 MHz if I
> >move
> >the cable to the 6m antenna port of my FT-847.
> >
> >Wayne Estes W9AE
> >Mundelein, IL, USA
> >
> >----
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>
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