freeview help

Discussion in 'Freeview & YouView' started by sajeel, Mar 6, 2013.

  1. sajeel

    sajeel
    Active Member

    Joined:
    Feb 24, 2013
    Messages:
    53
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    11
    Location:
    London (east)
    Ratings:
    +9

    I have a gym that has freeview.

    Here is the setup, aerial feed is split in 2 way to radio and tv, then fed into 4 way splitter to feed the 4 freeview boxes. The 4 freeview boxes are then fed by scart to 4 rf modulators and then output is back in 4 way splitter and then into 1 x 8way looped with 1x 6way to feed 9 analogue tvs on gym equipment. The signal is poor when splitter is used after rf modulators. if i plug each rf modulator 1 at time direct signal is good. I am planning of adding a variable active amplifier just before 1 x 8 way and 1 x6 way splitter to boost signal to 9 feeds ? also would you recommend to change 1 x 8way and 1 x 6way for 1 x12 way ?
    The 4 modulators are set up as follows 21,23,25,27 so the analogue machines can tune in regardless of channel setup on freeview box.
    Any advice appreciated sorry for long post.
     
  2. bow79

    bow79
    Active Member

    Joined:
    May 23, 2009
    Messages:
    881
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Leeds
    Ratings:
    +81
    Are you wanting each tv to have access to each freview box so it can tune in to any one of 4 programs?
     
  3. sajeel

    sajeel
    Active Member

    Joined:
    Feb 24, 2013
    Messages:
    53
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    11
    Location:
    London (east)
    Ratings:
    +9
    I can already see all 4 Freeview on tv as modulator has been set to
    21, 23, 25, 27 to avoided crosstalk.

    Just wanted to know if I should replace splitters with 12 way instead
    Of having 2 splitters and best amplifier to boost weak signal
     
  4. lbear

    lbear
    Well-known Member

    Joined:
    Mar 9, 2010
    Messages:
    2,117
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    83
    Ratings:
    +337
    First of all, I would check what UHF channels your local Freeview muxes are broadcasting on. Make sure the modulators are sending out signals far removed from this as modulator output and precise analogue tuning can be an inexact science. No point for example in using those channels if a nearby transmitter uses 22, 24, 28 and 30. (Your Freeview box should have a menu option to display the UHF channels or frequencies.

    Second, if all your TVs have the same or similar poor quality signal whether they are fed by the 8 way or 6 way splitter, your problem lies with the second "4 way splitter" which you are using as a "combiner" so the signals from the four modulators are shared between the 9 sets. Normally these are set up so a signal goes to a single input (which you are using to output) and is then amplified slightly to serve four outputs. At its worst, the amplifier built in might be feeding back slightly out of phase signals degrading the output.

    Looking at the Labgear site, they do not appear to do a distribution amplifier with four terrestrial inputs and multiple outputs. The nearest is a rather expensive one which has 4 satellite inputs, one terrestrial input and 12 outputs with provision of course for any satellite receiver to select which of the four LNBs to switch to. Almost certainly useless for your purposes and for the price you could get another 5 (possibly HD) boxes and just distribute the main aerial signal to a box under each set. If space is tight or mounting a completely separate box is impossible, something like this can be plugged into the SCART socket directly, their mains adapter will need a separate mains outlet. (Please note, this was a random search on that auction site and I in no way recommend that particular seller, especially because of the use of a counterfeit Freeview logo, or that particular model. Also, these do require good ventilation as many report them getting warm during use which is believed to reduce their working life.)

    If I can suggest a fairly inexpensive experiment: Screwfix do a 2 way passive splitter/combiner for £9 Feed two of your modulators into that and connect it to the first of your distributers as you already have. If that works, get another two (four into two, two into one). As you are combining signals, you should not need any amplification unless they signficantly reduce the signal. In that case, add two simple one to one amplifiers between the pair of two and the final one. Something like this:

    ........Modulator 1...Modulator 2....Modulator 3...Modulator 4
    ..................|...........|.........................|........|.................
    ..................Combiner 1.......................Combiner 2
    ..............................|...........................|................
    ...........................Amplifier 1............Amplifier 2
    .....................................|...............|.......................................
    ....................................Combiner No 3
    ..........................................|............................
    ...............................8 Way Distributor
    .................................|..............|||||||....................................
    .....................4 Way Distributor....7 Analogue TVs
    ..............................||..........
    .....................Remaining 2 TVs

    (Sorry about the need for the dotted lines, only necessary to separate the vertical connection lines properly)

    P.S. I hope you are familiar with the need for a commercial premises TV licence so you do not get a nasty call from the men in funny vans.
     
    Last edited: Mar 9, 2013
  5. winston2010

    winston2010
    Active Member

    Joined:
    Jun 28, 2010
    Messages:
    1,892
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    London
    Ratings:
    +190
    An amplifier as you suggest should do the trick. You need enough gain to overcome the loss in the splitters, probably around 12dB. I would't bother changing the 2 splitters for a 12 way.
     
  6. lbear

    lbear
    Well-known Member

    Joined:
    Mar 9, 2010
    Messages:
    2,117
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    83
    Ratings:
    +337
    Read the entire thread carefully and you will find one of the "splitters" is being used incorrectly as a combiner. My suggestion above takes this into account. If the signal is being degraded by the splitter not sending out a signal properly, no amount of amplification will improve it.
     
  7. winston2010

    winston2010
    Active Member

    Joined:
    Jun 28, 2010
    Messages:
    1,892
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    London
    Ratings:
    +190
    There is nothing wrong with using a splitter as a combiner. It is not incorrect. There will be a loss of approx 8dB but there should still be sufficient signal at this point for an amplifier. It should have sufficient gain to cover this loss plus the loss of the following splitter. Hey I made a mistake, about 20dB required not 12dB I said previously.
     
  8. sajeel

    sajeel
    Active Member

    Joined:
    Feb 24, 2013
    Messages:
    53
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    11
    Location:
    London (east)
    Ratings:
    +9
    Thank you ibear for such a detailed reply and winston2010 for your information. As ibear said i am using a 1 in 4 out splitter as a combiner and that's were signal loss is occurred if i plug direct into 8 way splitter signal is not as bad.
    I was thinking along on the same lines as your plan, as i reliased the 4 way splitter as combiner is the problem.

    I will buy 3,2 way combiner and 2 amplifiers and let you know how i get on.
     
  9. winston2010

    winston2010
    Active Member

    Joined:
    Jun 28, 2010
    Messages:
    1,892
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    London
    Ratings:
    +190
    Some of the loss is in the combiner, in fact around 8dB. The 8 way splitter will have even more loss around 12dB. Before spending money on 2 amplifiers and 3 combiners I suggest you only buy one amplifier initially and try that after the existing 4 way combiner. If it works, and I believe it will, you'll save some money. If it doesn't you can always then buy a second amplifier and 3 combiners.
     

Share This Page

Loading...