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Re: July 2001 President's Letter



Hmm? That's not the way it is done commercially, is it. The Master reference
station decides who transmits and when. The Slave transmitting station only
controls the digital data fed to his transmitter (no analog!), not when or
where it transmits. Even to get on the bird to communicate you must access a
specific ranging channel at an assigned time where synchronization is
obtained and then the uplink power and the traffic frequency slot/access
time is set (again, by the MRS, not the user!) ...

Bandwidth can be anything technology will support, larger or smaller than
what we have currently. However, the greater the bandwidth the more stations
would be "allowed" to access the bird (due to increased frequency slots).
Increased bit rate (more bandwidth) allows even more occupancy per
bandwidth.

What would be the minimum bit rate for aTDMA (Amateur TDMA)? I'm thinking
there is going to be a steep operator learning curve here...

And, would the days of random contacts as we experience now (most of us) be
gone forever?

----- Original Message -----
From: John Stephensen, KD6OZH <kd6ozh@gte.net>
To: John Wilcox <ns1z@agate.net>; 'Amsat BB' <amsat-bb@AMSAT.Org>
Sent: Saturday, July 21, 2001 2:42 AM
Subject: Re: [amsat-bb] July 2001 President's Letter


> No one else controls your equipment for TDMA any more than they do for the
> current FDMA system. Think of the timing information as a beacon. Today we
> control the amplitude and frequency that we use relative to the beacon.
>
> TDMA does require a large bandwidth so it would interfere with SSB users
on
> the same transponder. If both the S1 and S2 transmitters are activated at
> the same time with different receivers it might be possible to perform
some
> testing. The TDMA scheme discussed in the past on this BB would use a
> hard-limiting transponder so more uplink power would be required in the
> absence of the "capture effect" of the limiter. The AGC is a disadvantage
in
> this case as it reduces the SNR of the digital signal.
>
> 73,
>
> John
> KD6OZH
>
> ----- Original Message -----
> From: "John Wilcox" <ns1z@agate.net>
> To: "'Amsat BB'" <amsat-bb@AMSAT.Org>
> Sent: Friday, 20 July 2001 10:35 UTC
> Subject: Re: [amsat-bb] July 2001 President's Letter
> >
> > It sounds like a fun experiment but I wonder if the complicated
equipment
> > required and the idea of some other station controlling your equipment
is
> > going to fly with many satellite users???
> >
> > Since TDMA can be used on the current transponder, will we see any TDMA
> > activity soon?
> >
> > ----- Original Message -----
> > From: John Stephensen, KD6OZH <kd6ozh@gte.net>
> > To: Dan James <nn0dj@wiktel.com>; 'Amsat BB' <amsat-bb@AMSAT.Org>
> > Cc: <ve3frh@asmat.org>
> > Sent: Friday, July 20, 2001 12:20 AM
> > Subject: Re: [amsat-bb] JUly 2001 President's Letter
> >
> >
> >
> >
> > ----
> > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

----
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