Sky Box (UK) - Record Two Channels

Discussion in 'Apple TV and Home Theater' started by kolax, Apr 16, 2012.

  1. kolax macrumors G3

    Mar 20, 2007
    I'm with Sky (satellite provider in the UK), and have the Sky HD box. When I got it installed, the guy said that because there was only one dish on the apartment roof, I wouldn't be able to record one channel while watching another, since the Sky box has two satellite coaxial sockets.

    Now, I really don't understand why I couldn't just split the single satellite coaxial that I have into two using a splitter, and put both of those into the box.

    What is the reason why that wouldn't work? Would using a splitter cause the signal strength to diminish?

    I'd really like to be able to record two channels at the same time in my current setup.
  2. maturola, Apr 16, 2012
    Last edited: Apr 16, 2012

    maturola macrumors 68040


    Oct 29, 2007
    Atlanta, GA
    If you split the coax cable, all you do is splitting the signal, you will get the "same" channel on both, your Dish installation only support one Channel at the time (Single channel per carrier or SCPC). Those that support multiple channels (multiple channels per carrier or MCPC) actually have modulators that combined multiple channel into a single bitstream before being modulated onto a carrier transmitted, and then you need a small box (demodulator) that split the signal for each channel and feed it to a different decoder (your inputs on your receiver)

    Based on what your installer told you, you got a SCPC, i am not familia with Sky so i cannot confirm but I am just going with the info you provided.
  3. kolax thread starter macrumors G3

    Mar 20, 2007
    Ah I see.

    I always thought all channels went down the cable to my box and the box decoded which ever one you were watching.

    How can there be a communal dish for all residents in the apartment block if we all watch different channels?
  4. displaced macrumors 65816


    Jun 23, 2003
    Gravesend, United Kingdom
    Here's my layman's understanding:

    The satellite broadcasts its channels using transponders. Each transponder broadcasts on a particular frequency and at a particular polarisation (horizontal or vertical).

    The range of frequencies which the satellite's transponders broadcast on is split in two - high-band and low-band.

    Now, as I understand it, polarity isn't a problem - the box will receive horizontal and vertical polarities down the one coax feed. But the band selection is troublesome. The Sky box sends a signal back down the coax line to tell the LNB (the box at the end of the arm on the dish) which band to receive (hi-band or lo-band).

    So, to be able to record any two channels at once, you need a minimum of two lines (and a more complex LNB) so that both hi- and lo-band channels can be received.

    If you've ever peeked though the Sky box's hidden Installer menu, you'll see options to set the hi/lo-band cutover point as well as the method of signalling to tell the LNB to switch band. Also, if you've ever added a channel manually, via the Sky Guide, you'll have entered a frequency and set either Horizontal or Vertical polarity.

    Hope that helps!

  5. Seamaster macrumors 65816


    Feb 24, 2003
    There is a solution to this.

    I live in an apartment building with a communal dish, but have Sky HD and can record two channels.

    Sky+/HD usually requires bi-directional cabling to/from from the dish. Most communal systems only have cabling in one direction. What is required is a gizmo at the dish end and a gizmo at the box end. My Sky installer sorted it out for me when I upgraded from basic Sky to Sky HD.
  6. kolax thread starter macrumors G3

    Mar 20, 2007
    Did they install that for free? I don't know how many folk in my apartment block have Sky, though there is 12 flats.
  7. chazman88 macrumors newbie

    Jul 9, 2010
    First things first, you cannot "split" a sky feed.

    In basic terms your sky box controls the LNB (the bit that hangs in front of the dish) and effectively tells this LNB what to tune to. So you only get one channel from the dish to your box at any one time. To enable you to watch one and record another then you must have multiple feeds to your sky box. This is done by having multiple receivers built into one LNB. So you get multiple feeds from one LNB. You can get up to 8 feeds from one LNB so in a single house this is normally enough as it will allow you up to four independent boxes each watching one thing and recording another.

    If you are in a block of flats this normally works slightly differently. The chances are there is a communal dish somewhere which you all use. This dish then connects to what is called a multi-switch with lots of output feeds (up to 24 i think). This multi-switch takes all the information that the dish is receiving (all channels) and then your box effectively tunes the multi-switch and not the LNB on the dish. Each flat will normally receive 1 or 2 of the feeds from the multi-switch so that you can watch one and record another (if it is a very old installation then the chances are you will only get one feed, as it will have been installed pre sky +/HD).

    Unfortunately if you only have one feed coming into your flat then there is not much you can do about it. You would have to speak to the company that do the maintenance for your block of flats and see if they can add a second feed for you.

    Hope that makes sense.

    The units that Seamaster is talking about do exist and are more generally known as satellite signal stackers, but in my experience the cheap ones don't work very well and the ones that do work are VERY expensive. You will definitely get much better results with two dedicated feeds.
  8. Seamaster macrumors 65816


    Feb 24, 2003
    Mine works great. Cost me about two hundred quid over and above the normal Sky HD installation cost two years ago.
  9. benjaminl133 macrumors newbie

    Oct 23, 2012

    So thats mean i can't configure a multiroom from skybox for 2 channel with only 1 LNB?

    i'm trying to Connect my skybox with AV Sender to 2nd tv and wish that the 2nd tv able remotely switch channel without interupting the 1st tv channel.
  10. themoffster macrumors regular

    Apr 26, 2011
    my flat was like that - only one cable from the sky dish splitter into the flat.
    as i stayed on the top floor i went into the loft and saw that there were two empty ports on the splitter, so i plugged in another cable and ran it into my flat.

    bish bosh, second input and can use sky+ as it was designed.

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