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Posted by Andy Dingley on 01/25/07 14:07
On 25 Jan, 12:34, Toby Inkster <usenet200...@tobyinkster.co.uk> wrote:
> However, the distance from the Earth to the Moon is *thirty* *times*
> *further* -- just think about that distance --
In a nice hard low-loss vacuum. With massive groundstations.
Power isn't the problem in long-range radio comms, it's noise. Although
the distance is high and so inverse square law losses are too, then
there's less trouble with noise sources than you can find inside the
atmosphere.
Also Apollo did have long comms blackouts. There was never more than
one body (the Moon) in the way as they had a global network of
basestations (one was a ship now being scrapped on Teesside). Far side
of the Moon was still a hoel though.
> Comparing pre-1950s terrestrial communication with Earth-Moon
> communications is like comparing [...]
EME comms (Moonbounce) is twice as far and can be done with '50s
vintage high-end amateur kit in the 2m band.
1930s terrestrial comms was also surprisingly sophisticated. Look at
the cross-channel microwave link. There's little in the Apollo-vintage
comms that was fundamentally different from the best of the late '30s.
Some of the engineering was different, but not the physics. Magnetrons
and klystrons were much the same, travelling wave tubes were new but I
don't think any of the downlinks even used MASERs.
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