1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Why only one channel per cable on satellite ?

Discussion in 'General Satellite Discussion' started by jtallon, Feb 4, 2005.

Thread Status:
Not open for further replies.
  1. Feb 4, 2005 #1 of 16
    jtallon

    jtallon Mentor

    43
    0
    Nov 7, 2004
    This might be a stupid question, but it's been bugging me ever since we got Dish installed a few months back...

    In our previous house, we had Time Warner Cable. Love it or hate it, I got all my service (including HDTV) from a single cable to each room. That was a DVR with two HDTV tuners.

    Now, wish Dish and DirecTV, you need a separate cable to feed each tuner. I know you can 'stack' signals to some extent, but it seems to be a tricky art.

    Fundamentally, what is the difference that allows cable companies to send hundreds of channels through a single cable, whereas the satellite companies will only send one channel per cable ?

    I'm sure it is something simple, but like I said - its been bugging me ever since I tore up my brand new house to run 2 or 3 cables to each room for a DVR & OTA antenna setup, just to match what a cable company could have done with one cable...

    Thanks !
     
  2. Feb 4, 2005 #2 of 16
    Slordak

    Slordak Hall Of Fame

    1,476
    0
    Dec 17, 2003
    Satellite cabling is not carrying just a single channel at a time. These cables are actually sending all of the even or odd transponders for an entire satellite at once. If using Dish Network's "DishPro" scheme, they're band-stacking and sending every channel from the entire satellite at once. So this actually *is* a lot of bandwidth.
     
  3. Feb 4, 2005 #3 of 16
    Bill R

    Bill R Hall Of Fame

    2,498
    4
    Dec 20, 2002
    Some additional information to add to Slordak's informative post: Cable TV (analog) uses standard TV channels for all their tranmissions. All they do is put the signal on a channel and all your TV has to do is tune to that channel to pick it up. All the channels are available on each TV and the TV does all the "work" to tune them. With satelllite the channels are sent in a digital format and the satellite dish LNB receives the microwave signal from space, downconverts it to a signal that the receiver can decrypt and then sends it to your TV. Because the signal is digital a satellite receiver (or tuner in the case of two tuner satellite receivers) is necessary to tune each channel (actually groups of channels).
     
  4. Feb 4, 2005 #4 of 16
    jtallon

    jtallon Mentor

    43
    0
    Nov 7, 2004
    Even with 'digital cable', the cable companies are still only running one cable into a house. Is it true then that TV coming from a cable TV company, even if it is 'digital cable', is still much more compressed than what we get from Dish or DirecTV ?
     
  5. Feb 4, 2005 #5 of 16
    Greg Bimson

    Greg Bimson Hall Of Fame

    3,918
    0
    May 5, 2003
    This will probably be the strangest explanation ever seen, so pardon the goofiness...

    For cable, the headend (the place where all of the channels are gathered) transmits all the channels on a few wires. These wires are split to many homes. As a distribution scheme, all of the channels are pushed through the wire, and your television (or VCR, or cable box) filters to the one channel you wish to view. Your television (or VCR, or cable box) is what tunes the channel. Therefore, you have the ability to split the cables and add more televisions to tune to different channels.

    For satellite, everything is delivered to one of their Broadcast Centers, uplinked to a satellite, and beamed back to earth. Here is where things get tricky.

    The satellite receiver is loaded with information on how to decode the signals. When it comes time to tune to a specific channel, the receiver pushes a signal to the dish (actually to the LNB) and grabs the transponder on which the signal is transmitting. The receiver then decodes the piece of the transponder that contains the channel, and you see it.

    The receiver actually tunes the LNB to all odd or all even transponders to pickup the correct channel. That is why, in order to receive channels from two different receivers, the satellite dishes are outfitted with dual-LNBs. A multiswitch can then determine, from the request from the receiver, to tune one LNB to odd transponders, and the other LNB to evens. However, a receiver is needed for each request to decode any specific channel (the DirecTV Tivo and Dish Network PVR's that have two tuners then basically act as two separate receivers)
     
  6. Feb 4, 2005 #6 of 16
    rcbridge

    rcbridge Godfather

    252
    0
    Oct 31, 2002
    Bravo! That is a great basic explanation of how each system works I hope the person understood it. To add to that when you factor in Digital cable, that is why you need a STB for each tv, the decoding happens between the STB and the cable.
     
  7. Feb 4, 2005 #7 of 16
    JohnL

    JohnL Icon

    701
    0
    Apr 1, 2002
    I'll provide alittle more information. Since the LNBF has to switch states to provide the appropriate signal, the receiver needs complete control of the LNBF and or Switch. The only way a receiver can get the appropriate signal is from the LNBF's and or switches.

    All Satellite receivers provide Voltage for the LNBF and any connected switches. The receiver will provide different voltages and well as voltage pulses to get the LNBF's and or switches in the proper state. Since a single LNBF and or switch feed can only be in one state another receiver connected to the same feed would try to lock the same LNBF and or switch into a different state and only ONE of the two receivers would be able to get the satellite feed into the proper state so its plain an simply not possible for a single satellite feed to be split a number of times to provide a signal to more than one receiver or satellite tuner at one time.

    A Legacy Two Orbital slot feed can be locked into ONE of 4 possible states. A Dish Pro two Orbital slot feed can be locked into ONE of 2 possible states. This is the reason satellite receivers require a ONE TO ONE relationship between a Satellite Feed and EACH AND EVERY satellite tuner.

    John
     
  8. Feb 4, 2005 #8 of 16
    Stewart Vernon

    Stewart Vernon Roving Reporter Staff Member Super Moderator DBSTalk Club

    21,626
    391
    Jan 7, 2005
    Kittrell, NC
    Perhaps another way of looking at this, without requiring all the in-depth understanding of how the Satellite innards work...

    With cable you are getting a feed of all the available channels (whether it be digital, analog, or a combination). Your set-top box (STB) and TV are used to determine what channel you actually watch, but all channels are always available... so aside from signal strength issues, you can split all you want to multiple boxes/TVs and select a channel.

    Going backwards... with OTA (over-the-air) antennas, unless you are in a very unique location you either need a directional antenna (points at the stations) or an omni-directional antenna. An omni-directional gives broader range to receive signals, but doesn't always receives them well... a directional antenna is good, but if you have channels in different directions, you need a rotor connected to the antenna so you can adjust how your antenna points to get the best signal.

    Now for Satellite... The STB is just part of the equation, the part that works with your TV to select the channel you want to watch. The Satellite dish is like the antenna, and even though you point it at a particular satellite (or 2) in orbit, there is some fine-tuning needed like with a directional antenna-rotor combination... so the STB communicates with the LNB/Switches on the dish to help get the best signal for the channel you select to watch.

    IF you split the signal and connect to different STBs... you can get interesting results. Channels that require a different configuration at the LNB will cause problems since each STB will try to "align" things a different way... much like if you connected two rotor controls to your rooftop OTA antenna and tried to turn it in opposite directions from 2 rooms in your house.

    Maybe this, along with the techno-stuff helps?
     
  9. Feb 5, 2005 #9 of 16
    ebaltz

    ebaltz Hall Of Fame

    1,432
    0
    Nov 23, 2004
    With all that tech stuff going on, doesn't it kind of make the case the cable is the better solution, since it is easier and more flexable?
     
  10. **pinke_13**

    **pinke_13** Mentor

    32
    0
    Jan 26, 2005
    It may be easier and more flexible, but you have to remember by NOT using all of that bandwidth, it's NOT a true HD or Digital picture.
     
  11. JohnH

    JohnH Hall Of Fame

    7,802
    0
    Apr 22, 2002
    Since satellite is a national service, there are more channels(locals) to deal with. Consider there are currently 2293 channels on DISH Network and probably a similar number on DirecTV. Everyones locals cannot be on the same satellite. I doubt your Digital cable is dealing with as many as 500 channels.

    I am wanting to see what Cable or Telco does with Fiber into the Home.
     
  12. JohnL

    JohnL Icon

    701
    0
    Apr 1, 2002
    What are you talking about, DO YOU EVEN KNOW????

    HD is specific in its format, the two types of HD used by broadcasters TODAY are 720p and 1080i and both have to be compressed to fit in the OTA broadcast spectrum. Dish is rebroadcasting the same exact signal.

    Digital is Digital, all it means is the picture and sound are converted into digital bits ("0's" and "1's") and sent as those bits. Digital means nothing more, you should not even equate the term "Digital" with any type of Picture and or audio quality.

    I will say that very good Standard analog OTA PQ quality will almost always beat the "lossy" Digital picture on either DirecTV or Dish. Mpeg2 or any compression technique will result in image loss. The question is how much, alot of compression will yield a poorer picture as well as Digital artifacts.

    With all of that said a MPEG2 picture can look great, an almost exact copy of the analog picture with no perceived picture loss, but the scarcity of bandwidth and and the need to carry as many channels as possible result in a compromise that most subscribers find acceptable.


    John
     
  13. rcbridge

    rcbridge Godfather

    252
    0
    Oct 31, 2002
    Quote {I am wanting to see what Cable or Telco does with Fiber into the Home.}

    FTTH will have the same restrictions as cable (In market restrictions) but for additional VOD, PPV HD and other extras there is much room for those services.

    If they do it right it can be a very good thing!!
     
  14. SimpleSimon

    SimpleSimon Hall Of Fame

    5,468
    0
    Jan 15, 2004
    OK. Let's get to basics and over-simplify.

    A single modern RG-6 feed can carry up to 2GHz of signals. Analog "cable" uses about 800MHz (44-870MHz), and it's not compressed. Max is 136 channels @ 6MHz each. http://www.tinlee.com/FreqChart.htm

    A single DBS transponder set (half the bird) is 500MHz. 10 channels per TP, 16 TPs, 160 channels.

    Old school, unstacked, compressed, digital means roughly the same as cable - And you can still carry the analog "cable" on the same wire because DBS is carried from 950-1450MHz.

    Now, enter stacking. Second TP band at 1550-2050MHz (standard) or 1650-2150MHz (DishPro). So, we're now carrying over 300 channels on the wire - and STILL can have the analog feeds.

    If you want to go with super-stacking (conceptual only here), you can get up to 5 transponder sets ranging from around 300MHz to 3GHz. That's 800 channels, and you still have a little bit of room to backfeed a few (35 - VHF plus low CATV superband) analog channels around your house. This would require a new variant of diplexer - easy to build, just tweak a few values in the existing designs.
     
  15. rcbridge

    rcbridge Godfather

    252
    0
    Oct 31, 2002
    Quote {A single modern RG-6 feed can carry up to 2GHz of signals. Analog "cable" uses about 800MHz (44-870MHz), and it's not compressed. Max is 136 channels @ 6MHz each. http://www.tinlee.com/FreqChart.htm}

    Your chart is correct but you can actually carry multiple channels using Qam within a 6mhz bw.
     
  16. Stewart Vernon

    Stewart Vernon Roving Reporter Staff Member Super Moderator DBSTalk Club

    21,626
    391
    Jan 7, 2005
    Kittrell, NC
    Easier is subjective of course... and flexible is subjective as well. Currently no local cable company (I don't believe) is trying to carry anywhere near the sheer number of channels that Satellite companies are carrying once you consider all the international channels and local channels for every market.

    Satellite, to some extent out of necessity, is more complicated because it is accomplishing more than your local cable company is doing... but to the end user who only gets 180 or whatever channels, you don't see what is going on behind the scenes so it is understandable that can look on the surface confusing.

    Also... my local cable company still broadcasts the first 80 channels or so as analog... and around here analog quality is not good, and even when it is good it is not good across the whole range... maybe 20 channels will be good with 60 varying in quality because they don't seem to be able to reliably tune all 80 analog channels to the same level of quality. Pushing that through a digital box to add the digital channels on cable sometimes make the analog stations look even worse.

    Also in my area... when the power is out, cable and Satellite are out (I have no backup generator)... but when power comes back, I have my Satellite! Invariably, cable stays out longer than power around here... oh, and while I do get a little rain fade sometimes in a storm with Satellite... I get all sorts of problems with rain on cable, even though it shouldn't be a problem... it very much is around here.

    Maybe my cable is just crap... but they are a relative monopoly in the area in terms of that... so Satellite is the only other option, and for me it has been better by miles... also much better customer service from Dish than I ever dreamed of getting from my local cable company!
     
Thread Status:
Not open for further replies.

Share This Page