Sending/Receiving Satellite Frequencies

Name: Drake
Status: student
Grade: 9-12
Location: MA

Question: Why is the transmission frequency from
Earth to a satellite different from the frequency
that the satellite transmits back to Earth?
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Drake,

The reason the "uplink" frequency is different than the
"downlink" frequency is that these transmissions are
occurring at the same time, so the frequencies are
intentionally different to avoid interference.

Regards,

Bob Wilson
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Radio frequency waves -- are waves -- and when waves pass through 
the same regions of space at the same time they tend to produce 
interference patterns with one another. A similar thing happens 
when your drop two pebbles in a pond. This interference produces
more complex waves which would have to be sorted out at the 
sending and receiving stations. One simple way of minimizing 
the interference effects is to send the two signals at frequencies 
(wavelengths) that are NOT simple multiples of one another. In this 
way the receiving antenna can be constructed to reject the sending 
frequency and only pay attention to the receiving signal, and vice 
versa.
 
Vince Calder
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