Multiple Links & Amplifiers - Help Requested

Discussion in 'Satellite TV, Sky TV & FreeSat' started by imprator, Sep 28, 2004.

  1. imprator

    imprator
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    Hi.

    I have been looking into altering my existing Sky installation, but am not sure how to proceed, and would appreciate some advice.

    I am afraid my posting is rather long, but with limited knowledge I am not sure what to leave out. Hope you have the patience to read to the end!

    My present setup consists of one terrestrial aerial, one Sky dish with quad LNB, and one digibox. This box feeds the room in which it is installed, an adjacent room, and four more rooms in an attached second building.

    The existing (professionally installed) setup has a feed from the RF2 socket to the adjacent room, which has a Sky link installed. The RF1 socket feeds a Labgear MSE 121 two-way splitter/amplifier (gain is unspecified, but similarly designated models are listed on the Labgear site at 14 db), from which one cable leads to the TV in the digibox room, and the other leads to a 27 db masthead amplifier in the second building. The output cable from this amplifier leads to a 4-way splitter box, then to the 4 rooms in this building. None of these rooms have Sky links, and neither the amplifiers or the splitter box will allow a link to function.

    I would like to do two things;

    1/ Install a Sky + box and pipe the output from both this and the existing digibox to all rooms.

    2/ Install a Sky link in all rooms.


    My first problem occurred when I installed a Sky + box (in the main room). When linked in series with the existing digibox it produces such a strong signal that interference occurs on the Sky + channel on all TV’s, no matter which RF broadcast channel is chosen. An attenuator largely eliminates this problem, but reduces the power on the digibox and terrestrial channels to a degree that degrades their pictures (they go grainy). Reversing the cabling order of the Sky + and digibox just transfers the problem to the digibox RF channel.

    I have found a Skyplus Combiner at http://www.tvlink.co.uk/combiner.htm which would (I hope) equalise the signal from both Sky boxes at an acceptable level, and thus eliminate the above problem. Does this sound like the way to go? (The combiner would also allow the control of both boxes from all rooms equipped with a Sky link.)

    The second problem is how to get a working Sky link in all rooms. I have already bought a 2-way Global amplifier/splitter (model F120), and an 8-way model (F180), but have encountered problems. As soon as I install the F120 (connected to RF2 on either Sky box), the picture on all downline televisions becomes very grainy. I am guessing that the level of amplification from this unit is too low?

    Likewise, when I install the F180 unit (either in the existing cabling setup or downline from the F120) all downline televisions become extremely grainy. Again, I suspect the unit lacks sufficient amplification power?

    I am now hoping that I haven’t wasted my money by buying the Global units!

    I can’t locate any Sky link-compatible amp./splitters of greater power, so I am wondering how I can proceed. Would two bypass kits (one for each existing amplifier) work? I note that they only allow for the operation of one Sky link, but if I fit the Global amp/splitter units downline of the bypass units would that allow multiple Sky links to operate? Or is there another solution?

    My knowledge of this subject is limited to what I have read – I am all (limited) theory and zero practical experience, so feel free to criticise any obvious errors I may have made!

    I would appreciate any advice as to how I might proceed.

    Thanks.
     
  2. Fernsehman

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    I can't really answer any questions but from what I recall of the "Piping TV Around the House" eBook, it might help. See satcure.com.

    I think your T120/T180 amplifiers have a gain of about 6db. If you consider that CT100 cable attenuates the UHF signal by about 0.18dB per metre then simple maths tells you that the Amp will drive up to 6/0.18 = 33 metres of CT100 before the signal level is lower than the original. This ignores any additional noise of course so call it 25 metres to be safe.
     
  3. luggsie

    luggsie
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    ********************************************************


    I dont subscribe to SKY+ , nor a freeview box for that matter, but here is my twopenn'orth anyway. AFAIK SKY+ is identical to SKY RF-wise. Presently I have three SKY digiboxes fed from a quad LNB, all their outputs daisy chained by RF loopthroughs, starting with a weak terrestrial signal which has its own low noise booster of +14 dB or so right at the start. I only encounter interference when the digibox o/p RF channels are set too close together, or too close to the terrestrial channels (nos. 21 to 33 here). They seem to need to be spaced by minimum of 5 channels to prevent mutual interference. So I set the digibox channels to 45, 50, 55, etc. on their setup menus (services 4, 0, 1, select on a SKY remote). Given this the SKY digiboxes perform very well as regards interference. Is your freeview RF channel number too close to the SKY Rf channel.

    *********************************************************
    The second problem is how to get a working Sky link in all rooms. I have already bought a 2-way Global amplifier/splitter (model F120), and an 8-way model (F180), but have encountered problems. As soon as I install the F120 (connected to RF2 on either Sky box), the picture on all downline televisions becomes very grainy. I am guessing that the level of amplification from this unit is too low?
    *********************************************************


    Extra gain shouldn't be necessary really. Check if the TV's work one at a time connected to RF1 rather than RF2 without the F120. Something is zapping the F120, probably a short circuit on a TV input or passive splitter. Do not connect the o/p from RF2 directly, or even via the F120, to any TV's without a TV link in series, as a normal TV RF input connection looks like a short circuit to the 9v link supply. The DC o/p from the SKY box will shut itself off when this s/c happens, possibly taking the RF signal down also which *may* be what you are seeing.

    **********************************************************

    I can’t locate any Sky link-compatible amp./splitters of greater power, so I am wondering how I can proceed. Would two bypass kits (one for each existing amplifier) work? I note that they only allow for the operation of one Sky link, but if I fit the Global amp/splitter units downline of the bypass units would that allow multiple Sky links to operate? Or is there another solution?



    ********************************************************

    I use a Philex SLx4B as a splitter (Maplin) which has digital bypass and its own PSU. This acepts up to 4 remote magic eye links, which all control just the last digibox in the chain, and is short circuit proof to avoid the problems above. The F120 you mention seems to accept mutiple links but gets all its power from the digibox according to http://www.satcure.co.uk/accs/page15.htm, which doesn't make it clear if it is s/c proof. Hence the possible requirement for links present in all its outputs to isolate DC from the TV antenna connectors.


    ....and now back to something less interesting, my income tax return......

    john
     
  4. simon123

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    i have been a rigger for nearly 20 years, and a cai member for a long time. this type of job can be quite awkward

    sending one sky signal to as many point as you like with magic eyes isnt a probem.

    but when you want to send more sky box signals around the house this usually ends up with the analogue tv signals very noisy but not always low gain

    to get around this you could put all receivers in one room and loop them together with 1m fly leads with the last one being the magic eye compatable one

    the amps you have bought are fine

    best thing is ring a cai rigger in your area or you will never get it perfect

    cheers simon
     
  5. imprator

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    Thanks for the helpful replies.

    I will try putting the advice into practice at the weekend and see what happens. If there is no success I will follow simon's advice and call in the professionals!

    Cheers.
     

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