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I was watching a documentary on Intelsat 1 (also known as Early Bird) and some of the first live television sent over it.

Was there any particular video format or modulation used, special for the satellite transmission? Or, if it was just NTSC or PAL, which was chosen and how was that signal converted for use at TV stations on the ground to be transmitted to viewers locally?

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  • $\begingroup$ Intelsat was launched the 6th April 1965, PAL was introduced 25th August 1967. $\endgroup$ – Uwe Jul 29 '19 at 9:14
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From astronautix

Payload: Two 6 W transponders with 50 MHz bandwidth. No multiple access. 240 voice circuits or one TV channel.

Required bandwidth for one TV channel of this time was about 5 MHz. Therefore the TV signal was not AM modulated, FM was used for noise reduction.

The electronics of such an early communication satellite had to be small, lightweight, low power and simple to be as reliable as possible.

I think there was no TV specific electronic within the satellite and no TV system (60 Hz and 525 lines versus 50 Hz and 625 lines) dependant electronics.

The same satellite electronics was used to transmit telephone, television, telegraph, and facsimile. Anything channel and signal specific was done in the ground stations but not in the satellite.

A heavy, complex TV signal converter ( 50 to 60 Hz or 60 to 50 Hz) with a low MTBF could be used only on ground.

For the satellite there was no difference what kind of signals were transmitted.

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  • $\begingroup$ Thanks, so it seems that there was plenty of bandwidth so nothing special then for the TV signal. That last part about the conversion is what I'm curious about... perhaps out-of-scope for this site but do you know what they were using to convert between 50 Hz and 60 Hz? I'm assuming essentially some camera-pointed-at-tube-in-a-box? $\endgroup$ – Brad Jul 29 '19 at 15:40

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