[Ari Ben Canaan]

I realise that in satellite communication the frequency of the uplink has to be higher than the downlink.

This is in order to prevent 'swamping'.

I have two questions :

1.) Could we instead transmit the uplink at a lower frequency than the downlink ?

2.) What is swamping exactly ? I have been told that if the uplink frequency = downlink frequency then stationary waves will be formed and there will be no transmission of energy/signal. Is this correct ?

[Ari Ben Canaan]

bump

[Stonebridge]

My understanding of swamping is that it is the effect caused by the signal being too strong for the receiver, resulting in distortion in the receiver amplifier and degradation of the signal.
This happens in radio communication when, for example, a receiving station is too close to a transmitter.

I know no more than this. My next move would be to do a Google search, but I'm sure you can do that for yourself.

[vaseand]

There appears to be a number of practical reasons for this. One is that the satellite downlink is chosen to be the lower frequency because less power is required to transmit at lower frequency than it is to produce a wave of the same intensity at higher frequency. It is easier to supply more power on the ground so the uplink is set to be the higher of the frequencies.

Also at higher frequencies, the beam width is narrower (rayleighs criterion) and therefore satellites can be kept closer together without uplinks to other satellites interfering (maybe this is the swamping your referring to?).

[Ari Ben Canaan]

(Original post by vaseand)
There appears to be a number of practical reasons for this. One is that the satellite downlink is chosen to be the lower frequency because less power is required to transmit at lower frequency than it is to produce a wave of the same intensity at higher frequency. It is easier to supply more power on the ground so the uplink is set to be the higher of the frequencies.

Also at higher frequencies, the beam width is narrower (rayleighs criterion) and therefore satellites can be kept closer together without uplinks to other satellites interfering (maybe this is the swamping your referring to?).

Click Here

It talks about jamming and in the first line it talks about swamping. What exactly is happening in the diagram and how are they achieving said jamming by swamping ?

Now you spoke of interference if the satellites got too close. What interference were you referring to exactly ?

[vaseand]

Ah ok, that basically seems to be saying that you can jam a satellite by just sending a load of noise (random signal) at it. Then it becomes harder to pick out the actual signal over the noise, essentially you degrade the signal-to-noise ratio of the receiving satellite so that it can no longer pick out the real signal i.e. you 'swamp' it with noise.

If satellites are too close, then signals being sent to one satellite will also be picked up by nearby satellites.

[Ari Ben Canaan]

(Original post by vaseand)
Ah ok, that basically seems to be saying that you can jam a satellite by just sending a load of noise (random signal) at it. Then it becomes harder to pick out the actual signal over the noise, essentially you degrade the signal-to-noise ratio of the receiving satellite so that it can no longer pick out the real signal i.e. you 'swamp' it with noise.

If satellites are too close, then signals being sent to one satellite will also be picked up by nearby satellites.

Hmm, that makes sense.

Okay, so if the uplink and downlink of a lone satellite were the same frequency would you expect interference ?