Tech info. wanted - transponder, spot beam, etc.

[treiher]

Does anyone know where I can go to read-up on the whole satellite, transponder, spot beam, etc. to better understand it? I have a ton of questions about all this and don't yet know enough for my own satisfaction. For example, why can I choose so many different transponders? Why do some work and others don't? Why after I change it, does the receiver change it back? How does it decide which one and why? What's the difference between spot beam and transponder (despite the obvious)?

. . . that kind of stuff. Thanks!

[bryan27]

I don't know any place to read, but I can answer the questions you posted.

why can I choose so many different transponders?

Each DBS satellite slot (61.5,101,110,119,148) has 32 Transponders. A transponder(TP) is a frequency range much like a Broadcast TV channel has a frequency range. A DBS transponder is about 24 megahertz (MHZ) wide. TV channels are 6 MHz wide.

A DBS Transponder can transmit 1 Analog TV channel, or upto 12 Standard Digital TV Channels.

Why do some work and others don't?
There are 3 reasons. 1: The TP isn't active (it isn't transmitting). 2: The TP is owned by another DBS provider (IE: on Dish (E*) if you try to find a signal on 119 TP 24 you won't get any signal because that TP is owned by DirecTV). 3: The TP is on a spot beam and you are outside of the coverage area.

Why after I change it, does the receiver change it back? How does it decide which one and why?

Because when you change channels you are changing the TP your receiver is reciving. The data stream from the satellite tells the receiver where channels are located. The receiver stores this information and when you change channels the receiver changes to the TP where the chosen channel is located.

What's the difference between spot beam and transponder (despite the obvious)?

None. A spotbeam has 1 or more TPs. The only difference is that a CONUS TP is sent to the whole country and a Spotbeam TP is sent to a specific area of the country.

[Nick]

Good question, Treiher, and very clear explanation, Bryan. Even I could understand it. :)

[treiher]

Thanks Bryan27! That was very helpful. Think I'm starting to get it. I was surprised that Direct TV has a transponder on the same satellite. Does that mean that Direct TV and Dish share satellites launched by Echostar?

[Mike123abc]

No, they do not share satellites. The each have satellites at 110 and 119. Echostar has 2 satellites at 110, one doing transponders 1-21, and the other doing the rest of the transponders that Echostar has. DirectTV has a satellite at 110 also doing the 3 transponders that it has there.

See www.lyngsat.com for a listing of which satellites are where and what they are showing on each sat. 101,110, and 119 are the DBS main locations for the United states, with 148 and 61.5 being side satellites.

[jhall]

When you enter the point strength menu, your receiver will have satellite and transponder number in the defaults. You can navigate and get signal strength for any transponder by selecting the appropriate number and satellite location from the menu. When you exit the menu, the receiver returns to the channel it was on, or sometimes if it gets confused, may go to channel 101 or 580.
So if you want to quickly find out where a channel is, tune to it, then enter the signal strength menu and look in the boxes for satellite and transponder.

[treiher]

Thanks jhall and Mike 123abc! That answers another question for me which is why is it that you get good signal strength on some transponders, but it's listed as wrong satellite. Guess that's because it's a Direct TV transponder, not Dish.

Here's another one, though. People here seem to know which satellite and which transponder their programming guide comes through on. How do you tell that? I get the part about changing to a specific channel and seeing which satellite and transponder the receiver switched to. But the guide comes down all the time and whenever it needs to. Make sense?

[bryan27]

The guide information for the EPG comes from one of the transponders, also each channel has a guide for it's channel in the channel's data stream. Sometimes when you push the guide the receiver goes to the transponder where the EPG is located and downloads the information into the receiver. When you push the info button that information usually comes from the channel's data stream.

Much of the information can't be obtained with a DBS receiver, an MPEG-2 DVB receiver is used to find the specifics for each channel.

[P Smith]

Originally posted by bryan27
The guide information for the EPG comes from one of the transponders,
--> tranponder # for such extraction doesn't matter - it's could be changed any time ;
each channel have own SID and a lot of other flags,
some of the channels carry EPG, EEPG, DNLD, etc

also each channel has a guide for it's channel in the channel's data stream.
---> that's not true - only EPG/EEPG channel have the info and your receiver grabbing the data and keep in his memory(RAM)

Sometimes when you push the guide the receiver goes to the transponder where the EPG is located and downloads the information into the receiver. When you push the info button that information usually comes from the channel's data stream.
----> when you push Info or Guide button, your IRD just show you all the info from his memory (RAM) where is the Guide/Info already gathered

Much of the information can't be obtained with a DBS receiver, an MPEG-2 DVB receiver is used to find the specifics for each channel.
Any "Guru" should know the stuff !

[bryan27]

P Smith, I was trying to keep it simple. The data stream for each channel has EPG packets. When you tune to a channel the receiver also receives all the information in the channel's EPG. Some MPEG-2 DVB receivers will take these individual channel packets and turn it into text where you can see the text being sent from the channel's EPG packet.

When one has information not available in the guide the receiver tunes to the TP where the main EPG data is located and is downloaded while one is in the guide waiting. When one presses info while watching a channel and gets info not available then the info pops up that information comes from the EPG packets on that channel.