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



Hi All,
I am active on ATV on 2441.5 and 10,400. A P5 picture requires a -87 dBm, 
minimum bandwidth is 16 MHz, subcarrier is calculate seperately as it has a 
lower deveation that the video. Going to wider deviation actually increases 
the capture effect.
An AM VSB signal requires a -67 dBm for a P5 picture, but fits in a 6 MHz 
bandwidth. AM is cranky, requires linear amplification and even a slight non 
linearity tollerated on SSB will regenerate the lower side band.
FM ATV has it's advantages, 100 times less power, linear amplifier not 
needed, and a quality picture.

Art,
 KC6UQH
----- Original Message ----- 
From: "John B. Stephensen" <kd6ozh@comcast.net>
To: "Robert Bruninga" <bruninga@usna.edu>; <amsat-bb@amsat.org>
Sent: Friday, December 30, 2005 5:37 PM
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
>>
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>> ----
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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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