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Weak signal - physics at work

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S

stevech

Part of the Furniture
Lest you complain about your -80dBm WiFi signal being weak...

Voyager 1 is over 10 Billion miles away.
  • The path loss is about 300 dB (!)
  • Transmits data on 8.4GHz at 12 or 18 watts with a 3m dish
  • NASA's Deep Space Network dish antennas, e.g., Goldstone, are 30m diameter.
  • Receivers are narrow bandwidth
  • Low noise amplifiers are super-cooled
  • Data rate is on the order of 10s of bps


The Inverse Square Law at work.
 
Last edited:
If our devices had antennae as effective as that 30M diameter NASA Deep Space Network antennae - nobody would be complaining about weak signals. :)
 
Hi,
I could talk to astronaut when the orbit was close with ham rdioa hand held walkie talkie
with rubber duck antenna some time ago.
 
Hi,
I wonder how long it takes for the signal to arrive from Mars.
 
Anything weaker than -60 dbm is too weak for WiFi :(

Anyway, they should have gave it some writable storage so new info could be uploaded to it, so if aliens find it, they will be able to at least watch some anime.
 
Razor512 said:
Anything weaker than -60 dbm is too weak for WiFi :(
Click to expand...
True, if you want near-max speeds. at -70s its quite good enough for handhelds. at -80's it is getting kind of slow.
Such as it is with 20MHz channel width in 802.11.
 
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