extended C band

Pesawat · 03-15-2006, 01:49 AM

I am new in this technology.

Theoritically or Conceptually, C band allocation is 3700 - 4200 MHz (downlink) and 5925 - 6425 MHz (uplink).

What is the allocation for extended C band theoritically?
Why it is called 'extended' C band?

What is rain rate exceedance curve?
Can I make an exceedance curve using ITU-R Rec. P.837?

Thank you

Will.Spencer · 03-15-2006, 02:15 AM

Extended C-Band is TX: 5.850 - 6.425 GHz, RX: 3.625 - 4.200 GHz.

Super Extended C-Band is TX: 5.850 - 6.725 GHz, RX: 3.400 - 4.200 GHz.

It's "extended" into a new frequency range.

A rain rate exceedence curve, as I understand it, is a curve made by plotting points of rain rate which caused rainfade interference to exceed acceptable levels. 105 millimeters per hour of rain is a good rule of thumb.

I don't have a copy of 837, but if you have access, you also might look at these two:

P.838-2: Specific attenuation model for rain for use in prediction methods
P.839-3: Rain height model for prediction methods

Pesawat · 03-15-2006, 03:32 AM

Thank you for the reply.

I noticed something unusual on the super ext. c band.
The TX bandwidth is 875 MHz but RX bandwidth is 800.
Is this correct?

What do you mean by "a good rule of thumb"?

You said: "rainfade interference to exceed acceptable levels".
What acceptable levels do you mean?

what is the relation between exceedance curve and the concept of availability?

Thank you

PS:
I already have the P.838 and P.839
Both are used in P.618.
P.837 is the method to predict the rainfall rate
P.838 is the method to determine the attenuation constant (dB/km)
P.839 is the method to predict the rain heigt
and
all of them are used in P.618 to calculate attenuation due to rainfall

Will.Spencer · 03-15-2006, 11:20 PM

Quote:

Originally Posted by Pesawat

I noticed something unusual on the super ext. c band.
The TX bandwidth is 875 MHz but RX bandwidth is 800.

I hadn't noticed that. That's very interesting. Extended C Band is 575 Mhz for both TX and RX.

Quote:

Originally Posted by Pesawat

What do you mean by "a good rule of thumb"?

A "rule of thumb" is a rough but usable rule that is easy to remember and apply, but based more on experience and common sense than on science or math.

Quote:

Originally Posted by Pesawat

What acceptable levels do you mean?

Acceptable to me means "I can browse the web."

Quote:

Originally Posted by Pesawat

what is the relation between exceedance curve and the concept of availability?

As I understand it, the signal will be available on one side of the curve and unavailable on the other side of the curve. It's a bit too theoretical for my mind, but that is how I read it.

You have me really curious. Why all of the attention to rainfade? Are you trying to determine what dish size you need to use?

Pesawat · 03-16-2006, 02:17 AM

I've told you I am new in this technology. So I am a student trying to learn more about comsat. The topic i am trying to learn at the moment is about rain rate and rain attenuation. There are a lot things i cant understand. That is why I am asking for your favor to help me understand it. I apologize for being theorist, but 'you can browse the web' is not a professional answer that either can use. Everyone can browse the web. I can even buy a book for God sake.

Will.Spencer · 03-16-2006, 11:15 AM

By "I can browse the web", I mean "My satellite modem is receiving a strong enough signal that I can reliable transmit and receive packets, receive a DHCP lease, and browse web sites on the Internet via satellite broadband."

I'm not telling you to browse the web or buy a book, I'm saying that this is how I measure "acceptable levels" of signal quality.

Does that make more sense now?

For professional measurements, I log into the SMTS (Satellite Modem Termination System) and look at the signal levels in dBm.

Pesawat · 03-16-2006, 11:35 PM

:lol: :lol: :lol:
My apology to you sir. I misunderstood your answer. I am sorry.
Thank your for the explanation.