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Re: 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
>
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