investigating radio interferometry satilite communications

[Robert Miller]

I'm curious if it is possible to create a virtual dish size of 100 ft. by
using two
small matched dish antenna's pointing at the same satilite for example
Direct TV's
101 satilite to reduce rain fade.

I see many problems that can be overcome. For example the distance from the
satilite to each dish and the distance of the dish via their cable
connections would
have to be very exact. So the signals will line up properly.

Radio astronomers do the same thing but with analog signals. I am
attempting
to do this with a digital signal. The more difficult problem is that the
receiver
unit sends an alternating 13v and 18v carrier to the LNB. If I try a simple
T circuit it will act as a voltage divider and will not work.

Is there already a circuit that will divide these carriers to the LNB and
combine and pass the received signals back to the receiver?

Or does one need to invent the circuitry to accomplish this task?

Thanks in advance.

Robert

 

[Hans Michlmayr]

You'll have to synch & phase lock the two LNB's local ocillators
together, probably impossible to do with normal consumer LNBs.
Unless this can be done, nothing else is going to make the idea
work !

Hans

 

[no_one]

I suspect that 100 feet of seperation would not be sufficient to overcome
rain fade across the area of interest. What about just getting one of the
dishes that I believe is designed for use in the northern latitudes for a
little more gain?

 

[Robert Miller]

Is this possible on commercial LNB's? Would LNB's with this capability
be available somewhere? Anybody know a good place to look?

Thanks in advance.

 

[Vladimir Dergachev]

I'm curious if it is possible to create a virtual dish size of 100 ft. by
using two
small matched dish antenna's pointing at the same satilite for example
Direct TV's
101 satilite to reduce rain fade.

I see many problems that can be overcome. For example the distance from
the satilite to each dish and the distance of the dish via their cable
connections would
have to be very exact. So the signals will line up properly.

Radio astronomers do the same thing but with analog signals. I am
attempting
to do this with a digital signal. The more difficult problem is that the
receiver
unit sends an alternating 13v and 18v carrier to the LNB. If I try a
simple T circuit it will act as a voltage divider and will not work.

One thing to keep in mind is that radio astronomers do this to increase
angular resolution, not SNR.

Angular resolution is ~lambda/d where lambda is the wavelength and d is the
diameter of the entire scope.

SNR, however, simply depends on the total scope area - i.e. how much RF
power you were able to pick up.

Having better angular resolution would help if there were two satellites
nearby and you needed to tell one from the other.

best

Vladimir Dergachev

 

[Robert Miller]

One thing to keep in mind is that radio astronomers do this to increase
angular resolution, not SNR.

Angular resolution is ~lambda/d where lambda is the wavelength and d is
the
diameter of the entire scope.

SNR, however, simply depends on the total scope area - i.e. how much RF
power you were able to pick up.

Having better angular resolution would help if there were two satellites
nearby and you needed to tell one from the other.

best

Vladimir Dergachev

Originally my purpose was to limit rain fade that I was used to with Dish
Network.
Now that I work as an installer for DirecTV and have access to better
information
about how DirecTV works there is little need since their yearly average
downtime
is 48 min. 3 times a year. With their standard equipment. I have and can
use a
larger dish to improve the S/N ratio. However to get all 5 satilites I'd
need 5 such
dishes. I've determined that it is possible, but of no practical use since
the gain would
be minute. Though for someone with a Dish Network system it may still prove
worthwhile

Thanks

Robert Miller