[amsat-bb] Re: L band
John B. Stephensen
kd6ozh at comcast.net
Mon Sep 11 00:16:35 PDT 2006
We might be able to use the L receiver as a backup, depending on the final
digital transponder design, but it would only work well near apogee. The
digital transponder needs to work over 75% of the orbit so that it's just as
available as the U/V analog transponder. This mandates a phased array
antenna with multiple receive paths. It's unlikely that all receivers in the
array will fail so a backup receiver on another band isn't a big issue.
----- Original Message -----
From: "Bill Ress" <bill at hsmicrowave.com>
To: "John B. Stephensen" <kd6ozh at comcast.net>; "i8cvs"
<domenico.i8cvs at tin.it>; <jules at g0nzo.co.uk>; "AMSAT-BB"
<amsat-bb at amsat.org>
Sent: Monday, September 11, 2006 06:47 UTC
Subject: RE: L band
> Hi John,
> I have just re-read the Eaglepedia report of the San Diego meeting.
> I must admit I continue to be shaken by Tom Clark's early statement about
> his views on the L-Band situation and then with the table called "Band
> Usage" which states L-Band usage (for digital) "Discarded due to possible
> L-band loss". I realize that this was referring to DIGITAL band
> and that later a table called "preliminary power budget" includes 3 watts
> for a L-Band ANALOG receiver but I have been concerned that this position
> about digital L-Band is based on the unsubstantiated and unproven notion
> about the "government(s)" taking us off the air there.
> John, I think engineering decisions should be based, as much as possible,
> real facts and data - not a notion about the future.
> Now another question. Why can't the L-band analog receiver (if it remains)
> be used for digital modulation (i.e. digital backup). Down to an IF
> frequency or modulation detection frequency it shouldn't care if the
> modulation is analog or digital. Have I missed something?
> Regards and thanks for your patience and time responding to my posts.
> Regards...Bill - N6GHz
> -----Original Message-----
> From: John B. Stephensen [mailto:kd6ozh at comcast.net]
> Sent: Sunday, September 10, 2006 10:59 PM
> To: i8cvs; Bill Ress; jules at g0nzo.co.uk; AMSAT-BB
> Subject: L band
> One thing may not be clear to all AMSAT members. There is still an L-band
> receiver in the Eagle requirements document for the analog transponder.
> San Diego meeting recommendation was to move the digital transponder
> from C to S. So far, no decision has been made to eliminate the L-band
> analog uplink.
> The analog transponder has a U uplink so if L becomes inaccessible, it
> works. The digital transponder has no secondary receiver so its uplink
> frequency is more critical.
> > > I would like the AMSAT decision makers to detail the reasoning for
> > > dropping the L-Band Uplink like a hot potato besides the "Galileo"
> > > excuse. As yet, I can't find it in Eagelpedia.
> > > In view of Peter Blair's (G3LTF) paper (PLEAS SEE JULES LINK BELOW) I
> > > cannot see any rational for dismissing Eagle use of the L-Band
> > > Uplink allocation. I don't thing using the statement that "we will
> > > our L-Band allocation" is indicative of the much appreciated
> > > the team is bringing to the Eagle design process.
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