What's different between a receiver & transmitter antennas?

[Uri Bru]

Hello,

I'm currently working on satellite model for high-school compatition, and I'm not sure if there's a visual difference between a reciver & transmiter antenas (on satellites)...
Also, is it possible to satellite to recive a radio wave information from another satellite

Thank you

 

[Spectrum90]

I think there is no visual difference from one to another, but a satellite receiving radio wave information from another one, it's possible yes, some satellites are connected to transfer information one through another to then send it back to Earth at another location ex: From one side to another, only 1 satellite can't do the work alone.
Satellites are connected like a network, they receive and send informations from Earth one to another until one sends it back again to earth.
But to the visual difference, i think there isn't one, i don't know for sure.

 

[Uri Bru]

I think there is no visual difference from one to another, but a satellite receiving radio wave information from another one, it's possible yes, some satellites are connected to transfer information one through another to then send it back to Earth at another location ex: From one side to another, only 1 satellite can't do the work alone.
Satellites are connected like a network, they receive and send informations from Earth one to another until one sends it back again to earth.
But to the visual difference, i think there isn't one, i don't know for sure.

Thank you very much :)

 

[berkeman]

Hello,

I'm currently working on satellite model for high-school compatition, and I'm not sure if there's a visual difference between a reciver & transmiter antenas (on satellites)...
Also, is it possible to satellite to recive a radio wave information from another satellite

Thank you

Depending on the application, I can think of a couple of potential differences. Can you say what they might be? (Hint -- think about different applications that satellite communication support)

 

[berkeman]

Also, since this is for your schoolwork project, I would normally move this thread to the Homework Help section of the PF. I'll allow it to stay here in the EE forum for now, as long as posters remember to have you do the bulk of the work on this question...

 

[sophiecentaur]

Is your question actually about transmit and receive antennae on board the satellite? Are we dealing with broadcast or communication antennae here? Makes a big difference to the designs.
Have you looked at images (Google) of satellite transmit and receive dishes? You will notice they are the same shape (parboloids) and the differences will be mainly in diameter - depending on the power of the transmitter used and how strong the received signal is.
This could be a very sophisticated question and it's potentially way beyond High School level but, if you are concerned with TV satellite mounted antennae then you have to think about Footprint for the transmitting dish. Beam needs to be narrow (perhaps 1000km footprint on the surface and a distance of about 35000km) to make sure the satellite only serves a restricted area of the Earth. There are only so many channels available and the channels have to be re-used for nearby reception areas. How does the signal get up to the satellite? An Earth station can have a more powerful transmitter and that means the receive antenna can have lower Gain.
Give us some feedback about the details of your project brief.

 

[Vespa71]

what\s a 1000 km footprint?

 

[nsaspook]

what\s a 1000 km footprint?

For a satellite it's the coverage area on Earth from a signal beamed from satellite to Earth from a transponder or group of transponders using an antenna.
It might be a traditional parabolic reflector or a modern phased array used to electronically steer the focus and direction of the beam to Earth or on the Earth to receive that signal. The size of that footprint depends on both the transmit and receive antenna gain (size), transmit power, receiver sensitivity, type of modulation and a host of other factors.

For an example most large DBS commercial networks have two types and typically use much higher frequencies for the down-link (KU and up 12-20+ GHz band for smaller antennas with high gain for consumers) than the up-link (C 5-7 GHz band large dishes for the providers that also provide resistance to atmospheric effects like heavy rain)
1. A wide coverage beam(s) on one or more transponders on the same channel or group of channels for general coverage of a wide area footprint.

1. Spot beams on other transponder channels designed to provide specialized coverage (like local TV channels)
for groups of large cities each with a much smaller footprint

and yes, you can and do have satellite to satellite communications on some systems.

 

[Vespa71]

I assume it is a 1000 km diameter circle target on earth, then. Rather than a 1000 km² target?

 

[nsaspook]

I assume it is a 1000 km diameter circle target on earth, then. Rather than a 1000 km² target?

That should be the Radius distance (I think, it's been a while since I worked with this stuff) but it's not always a circle.

 

[Baluncore]

The principle of reciprocity says that the same antenna will work for transmit and for receive.
https://en.wikipedia.org/wiki/Antenna_(radio)#Reciprocity

The only visible difference may be the thickness of the higher power feed-line from a transmitter.

 

[sophiecentaur]

That's certainly the answer in a nutshell. The supplementary is "Transmitting to what and Receiving from what?"
Link budgets rule.

 

[Uri Bru]

Thank you all, it was very helpful

 

[berkeman]

Depending on the application, I can think of a couple of potential differences. Can you say what they might be? (Hint -- think about different applications that satellite communication support)

Thank you all, it was very helpful

But you didn't answer my question...

 

[sophiecentaur]

That should be the Radius distance (I think, it's been a while since I worked with this stuff) but it's not always a circle.

But does it make any significant distance in the context? We are talking in terms of Orders of Magnitude. When Engineers need km accuracy they use km and when they need mm accuracy, they talk in mm. Life's too short, chaps.

 

[sophiecentaur]

But you didn't answer my question...

I think we scared him off!
Engineering replies can be a bit overwhelming.

 

[Uri Bru]

I think we scared him off!
Engineering replies can be a bit overwhelming.

Sorry, I didn't see your comments until now...

But you didn't answer my question...

I'm not sure yet about all the details, it's a team project, and I'm in charge only on the model design... So i don't know about any difference between them, or even if there is one...

 

[berkeman]

I'm not sure yet about all the details, it's a team project, and I'm in charge only on the model design... So i don't know about any difference between them, or even if there is one..

Well, most satellite antennas will be parabolic dishes. What are most land-based, mobile antennas?

 

[Uri Bru]

Well, most satellite antennas will be parabolic dishes. What are most land-based, mobile antennas?

I'm not sure... I think they're also parabolic, aren't they?

 

[davenn]

I'm not sure... I think they're also parabolic, aren't they?

you sure ?

what sort of antenna does your car radio have?, what about the antennas on vehicles for CB, Ham or commercial
radio communications ?

The main places for terrestrial based radio systems using parabolic dishes is
for microwave links between sites

have a look on a cell (mobile) phone tower
you will see several large vertical antenna arrays for communicating with the mobile phone you carry
there will also be up to 3 small parabolic antennas for microwave band linking to other cellular towers,
generally in the 18 - 50 GHz rangeDave

 

[nsaspook]

But does it make any significant distance in the context? We are talking in terms of Orders of Magnitude. When Engineers need km accuracy they use km and when they need mm accuracy, they talk in mm. Life's too short, chaps.

It can depending on the orbit (non-geostationary) where the satellite footprint can be a swath or strip over a point on the globe that moves over time and is a place where you need to have your footprint in at that point in time to talk.

 

[sophiecentaur]

It can depending on the orbit (non-geostationary) where the satellite footprint can be a swath or strip over a point on the globe that moves over time and is a place where you need to have your footprint in at that point in time to talk.

Is the detailed shape and size of a footprint very relevant here? There is a huge range of footprints so I can't see how a 1000km radius or a 1000km diameter makes a lot of different to the basic point I was making. A domestic receiving dish cannot be anything like big enough to produce a beam that narrow and I was basically pointing out one significance between the antenna sizes. As neither we, nor the OP know what is required from his school project then we can only talk in very general terms. Non GEO adds further complication and more variations in dimensions.

 

[Baluncore]

Phased array antennas now make it possible to use digital signal processing to synthesise many dynamic spot beams.
That is much more difficult with parabolic dishes, particularly in lower orbits.

google images 'phased array satellite antenna'