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Posted by Ben C on 01/25/07 15:19
On 2007-01-25, Andy Dingley <dingbat@codesmiths.com> wrote:
> 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
Do you not somehow focus the wave? Using a dish for example on the
transmitter, so it travels parallel like a spotlight beam, or perhaps
you let it fan out a bit but not inverse-square law.
[snip]
>> 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.
People overestimate the rate of development of technology because of
computers. But other things haven't developed as fast, and a lot of
developments in apparently unrelated areas of technology have actually
come by way of fitting small computers into everything to replace
mechanical control systems.
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