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



The handbook indicates that a snow-free picture requires about 15 dB more
power than the minimum so 300 Watts would be best. Some type of digital
transmission would be much more power efficient.

73,

John
KD6OZH

----- Original Message -----
From: "John B. Stephensen" <kd6ozh@comcast.net>
To: "Robert Bruninga" <bruninga@usna.edu>; <amsat-bb@amsat.org>
Sent: Saturday, December 31, 2005 01:37 UTC
Subject: Re: [amsat-bb] Re: [ATNA] More thoughts about HAM TV from space


> According to the ARRL Image Communications Handbook, FM ATV uses 4 MHz
> deviation and a 5.8 MHz sound subcarrier so the signal is about 20 MHz
wide.
> The minimum required signal at the receiver is 7 microvolts or -93 dBm,.
If
> ISS is 350 km away the path loss is 153 dB at 2400 MHz. A 2 foot dish has
20
> dBi of gain so a minimum of 10 W EIRP is required.  100 W is more
realistic
> so that there is 10 dB margin.
>
> However, there are at least 3 standards for analog color TV so only a
> fraction of hams will be able to receive the signal. A digital signal that
> could be received on a PC would be better as the Internet provides the
only
> worldwide standard for image transmission. If the astronauts had the
> appropriate accessories for their PCs they could use the system. A 384
kbps
> link would provide enough bandwidth.
>
> 73,
>
> John
> KD6OZH
>
> ----- 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
> > ----
> > Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> > 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.
> Not an AMSAT member? Join now to support the amateur satellite program!
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----
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