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Re: Re: [ATNA] More thoughts about HAM TV from space



VSB AM requires more power for equivalent picture quality.

A digital system with approximately a 1 Mbps data rate is probably what's
viable at maximum range if the uplink is to use existing transverters (10
watts out) into a single yagi.

73,

John
KD6OZH

----- Original Message -----
From: "Robert Bruninga" <bruninga@usna.edu>
To: <amsat-bb@amsat.org>; <kd6ozh@comcast.net>
Sent: Saturday, December 31, 2005 14:04 UTC
Subject: Re: [amsat-bb] Re: [ATNA] More thoughts about HAM TV from space


> >>> "John B. Stephensen" <kd6ozh@comcast.net> 12/30/05 8:37 PM
> > FM ATV uses a... 20 MHz wide [signal].  The minimum
> >required signal... is... -93 dBm.  At 350 km away
> >the path loss is 153 dB at 2400 MHz. A 2 foot dish
> >has 20 dBi gain so a minimum of 10 W EIRP is required.
>
> But we also have to add that the path is 2000 km to
> the horizon, 1500 km when ISS is at 5 deg and 1200
> km when it is above 10 deg.  So we should probably
> plan for the 1500 km range which takes another 12 dB.
> Or would need a tracking 8' dish.  Bummer.
>
> What about VSB AM?  This would have 2 advantages.
> 1) ENable the use of simple readilly available MDS
> down converters infront of any TV set.
> 2) Reduces the bandwidth from 20 MHz to 6 which
> should get back about 5 dB.
>
> If we did not use the sound sub-carrier could we do
> it in 5 MHz?  We could use a 10W 2m FM downlink
> for the audio.
>
> >However, there are at least 3 standards for analog
> >color TV so only a fraction of hams will be able to
> >receive the signal.
>
> But we would use it as a bent-pipe transponder, so
> what comes down is what goes up.  In each country,
> what they see is what they transmit.
>
> Bob
> ----- Original Message -----
> From: "Robert Bruninga" <bruninga@usna.edu>
> To: <amsat-bb@AMSAT.Org>
> Sent: Friday, December 30, 2005 21:33 UTC
> Subject: [amsat-bb] Re: [ATNA] More thoughts about HAM TV from space
>
>
> > OOPS... Big change in the original ATV satellite premise:
> >
> > The opportunity I am working on is on the ISS, so
> > we cannot TX on 70 cm since that will probably be
> > the main uplink band for all the other ham stuff
> > on board.  SO I guess that means it will need to
> > be 2.4 GHz downlink.
> >
> > THus, all it takes to receive it is a standard MDS
> > downconverter which plugs directly into a TV
> > set.  OK, lets study that approach.  Do the link
> > calculations and lets see how much TX power
> > (to an omni) is needed for receiving on a 2' dish.
> >
> > de Wb4APR, Bob
> >
> > >>> mvonlanthen@vtx.ch 12/30/05 12:13 PM >>>
> > > 1 - The satellite rules were changed to allow HAM TV downlinks between
> > > 420 and 440 MHz.
> > > 2 - We could decide which of the five HAM TV standard channels to
> > > use:  421.25, 426.25, 427.25, 434.00, 439.25.
> >
> > hb9afo---------
> >
> > After short study, it's not permitted to use the 1200 MHz band in the
> > sens space-earth as i was proposing in my precedent message. The best
> > solution would be to use DATV on 430 MHz but only between 435 et 438
> > MHz, the sole permitted space segment in Europe.
> >
> > So use the 434 MHz channel pushed to 436,5 MHz per example for the
> > downlink space to earth and 1200 MHz for uplink earth to space. But use
> > DATV instead of normal ATV, it would be much easier.
> >
> > 73
> > michel hb9afo
> >
> > _______________________________________________
> > ATNA mailing list
> > ATNA@mailman.qth.net
> > http://mailman.qth.net/mailman/listinfo/atna
> > ----
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> > Not an AMSAT member? Join now to support the amateur satellite program!
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> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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