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Re: re AO-40:tracking in USA xmsatellites as test sig



You would just see the noise power go up on these frequencies.
I went out with a 17db horn and an icom r3 and measured the sat freqs.
XM1
085 west xm1 2333.54 bw1.5mhz 2343.91 bw1.5mhz
115 west xm2 2342.26 bw1.5mhz 2335.35 bw 1.5mhz.

Set to am or ssb and it will appear as nouse power.


I tried it with am mode to an icom R3 into a 17 db horn and its real easy to
find, in fact
I was wondering why I got noise peaks there before, not knowing these sats
were there.
They arent strong enough to intermod but plenty strong to see with probably
almost any
converter thats slightly alive, its probably designed to work into a patch
antenna thru some trees
without breaking up.

The two frequencies use a bank of 16 228 watt twta's for a total RF power of
3Kw per channel into a
1.5 MHz bandwidth, with 2 transponders per sat there. see
http://spaceflightnow.com/sealaunch/xm1/
http://biz.yahoo.com/e/l/x/xmsr.html



----- Original Message -----
From: "Cliff Buttschardt" <cbuttsch@slonet.org>
Cc: <amsat-bb@AMSAT.Org>; <forum@amsat-dl.org>
Sent: Sunday, July 08, 2001 11:19 AM
Subject: Re: [amsat-bb] re AO-40:tracking in USA xmsatellites as test sig


> Hello all! This portion of your original message was very
> interesting.  We really need to know about signals near AO-40
> downlink that can be used for S band receiver checks.  Any
> additional information you might have would be appreciated.
> Cliff K7RR
>
> realfun451 wrote:
> >
> > The xm1 and xm2 satellites are on the air, xm1 at 85 west provides some
> > pretty strong
> > data carriers, at 2333.5 at -52 dbm, noise -87 at that wide
> > bandwidth.
> >
> > Just turned over to xm1 in a 3khz bw (about a 1 meg bandwidth to the
> > carrier)
> > 2333.500 -67dbm in 3 k bandwidth 2332.7-2334.2 with spectral regrowth at
> > 2334.571 -83 dbm. So this signal is 25 db stronger than ao40 ought to be
> > good for
> > some testing or something. Talk about a monster signal.
If we look at a 3khz chunk of the 1.5mhz bandwidth,
its 1/500 of the transponder bandwidth, or 3kw/500 = 6 watts of power we are
looking at,
and it is a conus only beam pattern, then from my off the cuff c band dbw
figures, a 6 watt transponder
on conus is 32 dbw in a 36 bandwidth, knock the bandwidth down and the power
up:
500*6*36/1.5 = 72000     10log72000=48.35db+32dbw=80.6dbw 1.5mhz bw
Which is 18.83dbw/hz

Next, plug power and the info on the web pages above into one of those link
calculation spreadsheets:
takes 66.9 dbw to do the same thing. Its 5.14dbw/hz by the spreadsheet
adjusted for my measured downlink
power coming down.

OK now look at a 200 watt transponder for the directv sat, listed at
48-53dbw
on http://www.geo-orbit.org/sizepgs/eirporgcharts.htm website.
Well if the xm sats are 11 db more power we are talking pretty reasonable
figures here.



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