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Re: July 2001 President's Letter



I don't see any reason that we must copy a commercial system exactly. Hams
could use automatic link establishment on our HF radios but we don't. If
people want to tune around manually and listen to different time slots I
don't see a reason to prevent it. It enables random contacts.

73,

John
KD6OZH

----- Original Message -----
From: "John Wilcox" <ns1z@agate.net>
To: "John Stephensen, KD6OZH" <kd6ozh@AMSAT.Org>; <amsat-bb@AMSAT.Org>
Sent: Saturday, 21 July 2001 10:58 UTC
Subject: Re: [amsat-bb] 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
> >
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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