Swamping in Satellite Communications

In summary: A satellite would normally get a very weak signal from both ground stations, because of the distance, and most receivers have delayed AGC, meaning that no AGC is applied for very weak signals in order to get best sensitivity.So, AGC desensitization due to ground stations is not normally a problem.
  • #1
elemis
163
1
What would happen if an uplink and downlink had equal frequency. I know 'swamping' would occur, but what IS swamping ? Would stationary waves be set up ?
 
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  • #2
The local strong signal transmitter would totally desensitise the receiver and as a result the receiver would "hear' little to nothing of the weak signal coming from a distance

ie. the transmitter would "swamp" the receiver

cheers Dave
 
  • #3
davenn said:
The local strong signal transmitter would totally desensitise the receiver and as a result the receiver would "hear' little to nothing of the weak signal coming from a distance

ie. the transmitter would "swamp" the receiver

cheers Dave
I'm not sure I fully comprehend.

You're saying that the transmitter would somehow overpower a receiver thousands of kilometres away from it ?

How is that possible when microwaves are line of sight ?
 
  • #4
No... the local transmitter would desense the local receiver so that the local receiver be it the ground station or the one in the satellite wouldn't be able to hear anything from the distance.

Each local transmitter would desense each local receiver ok ? :)

being line-of-sight is irrelevent

Dave
 
  • #5
Is it mainly because the receiver usually has AGC which turn the gain down in presence of a strong signal of the desired frequency? So it won't "see" the weaker signal from farther away?
 
  • #6
That would also play a part

So it all goes to show why they use separate uplink and downlink freqs so they don't have all those engineering hassles :)

Dave
 
  • #7
One ground station could overpower the receiver of a satellite receiving another station if the stronger station was also in the beam-width of the satellite's antenna and much stronger.

Stations on the ground are unlikely to directly interfere with each other since both would be using dish antennas pointing upwards toawrd the satellite. So they would not be in each other's antenna pattern.
 
  • #8
davenn said:
That would also play a part

So it all goes to show why they use separate uplink and downlink freqs so they don't have all those engineering hassles :)

Dave

What is the other reason of desensitizing?
 
  • #9
yungman said:
What is the other reason of desensitizing?

It depends on the type of modulation used.

FM receivers have a capture effect where only the strongest signal is followed. So, you don't even hear the weaker signal.

Data signals use a lot of different modulation systems, but if you don't get FM capture, the best you will get is corrupted data where you get data from both ground transmissions.

A satellite will usually get a very weak signal from both ground stations, because of the distance, and most receivers have delayed AGC, meaning that no AGC is applied for very weak signals in order to get best sensitivity.
So, AGC desensitization due to ground stations is not normally a problem .

Single sideband transmissions would have the problem of just producing two voices on top of each other with the stronger one being louder. So it would be hard to hear the weaker one while the stronger one was talking.
 

1. What is swamping in satellite communications?

Swamping in satellite communications refers to the phenomenon in which a satellite receiver becomes overloaded with too many signals, causing a decrease in the quality of the received signal.

2. How does swamping affect satellite communications?

Swamping can cause interference and reduce the signal-to-noise ratio, leading to errors and degraded performance in the communication system.

3. What are the main causes of swamping in satellite communications?

The main causes of swamping include high transmit power of the satellite, signal reflections from nearby objects, and interference from other neighboring satellites or terrestrial transmissions.

4. How can swamping be prevented or minimized?

To prevent or minimize swamping, satellite designers can use directional antennas to reduce the amount of energy radiated in unwanted directions, employ frequency and polarization diversity techniques, and carefully plan the placement of satellites to avoid interfering transmissions.

5. How does swamping affect the overall performance of a satellite communication system?

Swamping can significantly degrade the performance of a satellite communication system, leading to increased error rates, lower data throughput, and decreased reliability. It can also cause interruptions or complete loss of communication in severe cases.

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