Krister Sundelin
E-learning Producer (2020–present)Feb 16

The Voyager 2 is now over 12 billion miles away. Even at that distance,
does the signal still stand out like a lighthouse against the
background, or is it hard to pick out?
Hello, Mark Oglesby !

Q: The Voyager 2 is now over 12 billion miles away. Even at that
distance, does the signal still stand out like a lighthouse against the
background, or is it hard to pick out?

A: The radio operates at 23 watts. The radio antenna in your smartphone
typically uses 3 watts.

So to even be able to receive it, you need this:

And even then, Voyager has to send at 160 bits per second for that
antenna to receive the signal.

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Aris Spanos
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Aris Spanos
So, does the signal still stand out like a lighthouse against the
background, or is it hard to pick out?

Tony Flury
23 W is minuscule, given the distance. The only way that the signal
stands any chance of being received is that :

They know where Voyager is and are constantly monitoring it.
They know what frequency it uses and how tightly bound that is.
They know the structure of the signal.
If it was a broadcast wide band radio signal and they had to start
searching the whole sky from scratch the search would take a long time.

If the broadcast was in visible light, then it would be utterly
invisible to the naked eye - even a 1000W lamp would be imperceptible at
the distance from Earth to Voyager. Thankfully radio receivers and
decent electronics are far better at picking up weak radio signals, than
our eyes are at picking up faint light sources.

Michael Wilkening
I doubt our feeble eyes could see a ten million watt light from that
distance.

César Del Solar
If all 10 million watts were aimed at the Earth, then maybe

Tami Stone
· Feb 20
Space communication nowadays doesn’t usually use a single carrier
transmitter, so there is no real ‘spike’ to stand out. It usually makes
digital changes in the noise floor to convey information. Think of
random little lumps and bumps periodically forming in a blanket spread
out over a vast area. That is how signals are sent and received,
completely different from a single channel radio carrier with a narrow
bandwidth and all its power concentrated from within.

John Shelly Thomas
The Voyager spacecraft also have high-gain antennas (“high-gain” in
comparison with a cell phone antenna).

I am not an engineer, but I do know enough about RF propagation to say
this: to receive a cell phone signal from that distance would require at
least 10 dB, probably more like 25 dB **additional** earthbound antenna
gain than the big dish in the picture.

Jim Lux
Way more than 25 dB. They use the 70m antennas for Voyager and it’s
X-band (8.42 GHz) - It’s a bit more than 74 dB gain.
The antenna on Voyager is 3.7m and has a gain of 48 dB.
The transmitter is book-kept at 40.9 dBm, which is more like 12 Watts. I
doubt they’re “backed off” 3 dB, but that’s from the carrier downlink
design control table on page 26 of the book that describes Voyager telecom.

Voyager is slower than light ( c ) by a factor of about 30,000 , so a
one way trip to our very nearest neighbor star would take about 120
millenia = 120,000 years !

On 7/03/2023 8:47 am, casagiannoni@optimum.net wrote:
>
>
> Voyager is slower than light ( c ) by a factor of about 30,000 , so a
> one way trip to our very nearest neighbor star would take about 120
> millenia = 120,000 years !

Yes, amazing how people don't understand basic math.

>
>Voyager is slower than light ( c ) by a factor of about 30,000 , so a
>one way trip to our very nearest neighbor star would take about 120
>millenia = 120,000 years !

I suspect that my factor estimate of 30,000 should be higher, so trip
to nearest neighbor star would be longer.

On 3/6/23 13:47, casagiannoni@optimum.net wrote:
>
>
> Voyager is slower than light ( c ) by a factor of about 30,000 , so a
> one way trip to our very nearest neighbor star would take about 120
> millenia = 120,000 years !

Yes.
But if we found a alien built item like "Voyager" visiting
from another solar system,
Would the importance of this discovery be very different
if it was 120,000 or 1.2 million years old?

No. The importance of this earth shaking discovery
would greatly change the way we viewed our human
existence on our planet.

Finding that there is intelligent life in the universe
other than us would change us.

Quit thinking there is nothing important beyond
the span of your own life.