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<DIV><SPAN class=906194519-07062011><FONT size=2 face=Arial>Hi
zusammen,</FONT></SPAN></DIV>
<DIV><SPAN class=906194519-07062011><FONT size=2
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=906194519-07062011><FONT size=2 face=Arial>Habe folgende
interessante Konversation in der Amsat
Liste mitbekommen.</FONT></SPAN></DIV>
<DIV><SPAN class=906194519-07062011><FONT size=2 face=Arial>Damit wäre BPSK eine
Idee um Energie zusparen und somit mehr Daten runter
zubekommen.</FONT></SPAN></DIV>
<DIV><SPAN class=906194519-07062011><FONT size=2 face=Arial>Einen BPSK Modulator
hätte ich auch gefunden (<A
href="https://wiki.mur.at/sat/TechCommunicationRadio">https://wiki.mur.at/sat/TechCommunicationRadio</A>),
was meinen die Ap Leiter?</FONT></SPAN></DIV>
<DIV><SPAN class=906194519-07062011><FONT size=2
face=Arial></FONT></SPAN> </DIV>
<DIV><SPAN class=906194519-07062011><FONT size=2 face=Arial>ciao lg
Robert</FONT></SPAN></DIV>
<DIV><SPAN class=906194519-07062011><SPAN lang=DE>
<P>------------------------------</P>
<P>Message: 8</P>
<P>Date: Tue, 7 Jun 2011 10:00:27 -0400</P>
<P>From: "Bob Bruninga" <bruninga@usna.edu></P>
<P>Subject: [amsat-bb] Re: PSK v. APRS</P>
<P>To: "'Trevor .'" <m5aka@yahoo.co.uk>, <amsat-bb@amsat.org></P>
<P>Message-ID: <059301cc251b$414f1bf0$c3ed53d0$@edu></P>
<P>Content-Type: text/plain; charset="us-ascii"</P>
<P>> My pet hate is AX.25 1200bps FM [on] satellites...</P>
<P>> ...But the reason AX.25 1200bps FM is still used </P>
<P>> for new satellites is because there's so much </P>
<P>> infrastructure, TNC's, PC software etc, already </P>
<P>> inplace, it's the easy option. </P>
<P>Actually, there is another very important reason. Link budget.</P>
<P>With AX.25 one can have a 2W transmitter on a cubesat which has enough
power</P>
<P>to hit an HT on the ground with a whip antenna. The same cubesat running</P>
<P>BPSK might be restricted to only 200mw.</P>
<P></P>
<P>The difference is the Duty Cycle. The AX.25 packet only lasts 1 second
say</P>
<P>once every 10 seconds for an average power of 200mw. Which is the same</P>
<P>power as the continuous power of the BPSK (200 mw) which is all there is</P>
<P>available from the cubesat bus.</P>
<P>But the advantage of the AX.25 BURST mode is 10 TIMEs the RF power to the</P>
<P>user on the ground.</P>
<P>For FM mobile-to-mobile satellite communications on OMNI antennas, that
is</P>
<P>why we use AX.25, to extend satellite links to mobiles.</P>
<P>There are of course other issues and BPSK does have better performance
for</P>
<P>the SAME power, but as you say, there are not that many mobiles with SSB
and</P>
<P>all the hardware necessary to auto-tune the radio to track the Doppler.</P>
<P>Bob, Wb4APR</P>
<P> </P>
<P> </P>
<P>------------------------------</P>
<P>Message: 9</P>
<P>Date: Tue, 7 Jun 2011 15:16:47 +0100 (BST)</P>
<P>From: "Trevor ." <m5aka@yahoo.co.uk></P>
<P>Subject: [amsat-bb] Re: PSK v. APRS</P>
<P>To: amsat-bb@amsat.org, Bob Bruninga <bruninga@usna.edu></P>
<P>Message-ID: <158528.63750.qm@web27204.mail.ukl.yahoo.com></P>
<P>Content-Type: text/plain; charset=iso-8859-1</P>
<P>Hi Bob,</P>
<P>I accept what you are saying about burst mode but it's possible to develop a
BPSK system that does burst mode too. </P>
<P>A BPSK system with Forward Error Correction can offer a 16 dB advantage over
AX.25 1200 FM. </P>
<P>As you say there's loads of FM rigs out there so receiving AX.25 is simple
and that's the reason everyone still uses it but for the future we should be
looking to more efficient means of communication.</P>
<P>73 Trevor M5AKA</P></SPAN></SPAN></DIV></BODY></HTML>