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Any pitfalls in a 40m satellite cable run?

Discussion in 'Satellite TV Forum' started by highly_defined, Apr 26, 2008.

  1. highly_defined

    highly_defined Member

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    Guys, I've installed a dish at the end of my garden (only place it can go) which means I'm going to have to run 40 metres of cable to my Humax DCI2000. Will I experience problems with signal loss over this run? Should I go for a particular type of cable?

    Thanks
  2. ase001

    ase001 Member

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    Use the very best cable and you may need a booster. I'v run 30m of cable and unfortunately I didn't use a quality cable and I get significant signal loss. I've put a in line signal booster and this helped but I still have problems. The best results I've managed to obtain, is by fitting the in line booster mid way in the cable run. I think I'm going to have to replace the cable or re-site the dish.

    You need to look for a low capacitance cable, Maplin's sell this and it's about £1.90 metre I think?

    These boosters are available from Ebay for about £3+pp and from Maplin's they £7ish I think and they take the power directly from the coax?

    I'm not sure if these in-line booster affect motorized dishes you will have to read up on them.

    Keep us posted on how you get on please?
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  3. flashgordon1952

    flashgordon1952 Guest

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    from my experience with amateur radio loses can be a problem with runs that long obviously the highest possible quality cable used and a booster will be needed. try running the cable underground in a plastic pipe or hollow cable again reason for this is protection from the elements. personally i would only do this in extrems cases. is it possible (if it exists) to run the cable to a remote box and wireless it to a receiver (like the old rabbit boxes?)
  4. fernandez

    fernandez Active Member

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    This advice from Satcure

    "WF125 cable is thicker, stiffer, and has lower losses than the cables above. Recommended for long LNB connections (e.g. over 40 metres) or where signal loss must be minimised. Note, however, that WF125 is stiff and should not be connected directly to indoor equipment as it can put excessive strain on the connector. We recommend that you use a threaded coupler and a short length of more flexible cable for this connection. We supply twist-on "F" connectors for this cable. (You can not fit a rubber boot to a WF125 connector so use self-amalgamating tape).

    WF125 can be connected directly to the LNB but the same comments about additional weight and stiffness apply. It can put extra strain on the connector and the extra weight can cause the LNB support arm to bend."


    http://www.satcure.co.uk/tech/cable.htm#type
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  5. Alan Mac

    Alan Mac Member

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    I think you will probably be OK with a 40 m cable run of CT100 / WF100 (or better), without requiring an amplifier. I have a satellite dish at the far end of the garden from the house (the only suitable location) and the cable is 100 m long. This does require an amplifier, about 35 m from the LNB end, but your 40 m cable may not require an amplifier. Fitting an amplifier when it is not needed may actually degrade the overall noise performance of the system.

    What matters is not the cable signal loss as such but the degradation in signal to noise ratio at the satellite receiver demodulator input. This degradation is likely to be be less than 0.01 dB for a 40 m CT100 cable (or its equivalent) and very slightly better for CT125 (but the improvement (of CT125 over CT100) for a 40 m cable length would be very marginal).

    If we assume:
    LNB Noise figure = 0.7 dB
    LNB minimum conversion gain = 50 dB
    Loss of 40 m of CT100 satellite cable at 2 GHz = 11.6 dB
    Noise figure of satellite IF receiver = 10 dB


    The Overall Noise Factor = F1 + (F2 - 1) / G1 + (F3 - 1) / G1 G2 + -----

    In our case:

    F1 = LNB Noise Factor = 1.174898
    G1 = LNB conversion gain = 100 000

    F2 = Noise factor of 40 m of CT100 cable = 14.45
    G2 = Gain of 40 m CT100 cable at 2 GHz = 0.0692

    F3 = Noise factor of satellite receiver (IF) = 10

    So the overall noise factor with the 40 m cable included:

    = 1.174898 + (13.45 / 100 000) + (9 / 6920) = 1.176332
    = 0.7053 dB noise figure

    So the 40 m cable degrades the noise figure by 0.0053 dB, which should have negligible practical effect.


    [If the cable was much longer, say 100 m, then:
    the overall noise factor using the 100 m cable is:

    = 1.174898 + (793 / 100 000) + (9 / 125.9) = 1.254313
    = 0.984 dB noise figure overall (for 100 m CT100 cable), nearly 0.3 dB degradation].

    In practice there will be mismatch losses at the cable ends which should be added to the cable loss. On the other hand, the assumed conversion gain for the LNB is probably on the pessimistic side.


    Alan
  6. ase001

    ase001 Member

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    Maplin's have both CT100 and CT125 coax in but it's a bit pricy, any suggestion where to buy?
  7. fernandez

    fernandez Active Member

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    Decent quality cable isn't cheap anymore.
    A quick google shows that the average price per metre is around £1.50 when bought as cut lengths, however Satcure sell 100M reels of WF125 cable by WEBRO (CT125 equivalent) for £59.95 (just under 60p/Metre)
    So, 40M as a cut length = £60 or 100M on a reel = £59.95
  8. Alan Mac

    Alan Mac Member

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    As the noise figure calculation demonstrates, there is no real performance benefit in using WF125 (over WF100) for a 40 m cable run (and even less for 30 m !) There are also some practical disadvantages (bend radius, fitting connectors and of course the price). I would go for WF100.

    Satcure sell WF100 cable for £24.95 per 100 m reel.


    Alan
  9. SamRadford

    SamRadford Active Member

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    As stated on that Satcure page, it's better to use a slightly larger dish to compensate for a long cable.
  10. mrdinkle

    mrdinkle Member

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    I am intending on a 30m run at bottom of my garden as I no like heights.

    will this be ok?
  11. SamRadford

    SamRadford Active Member

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    Are you certain? CT cable hasn't been manufactured since Raydex was bought out several years ago. More likely it's a cheap "equivalent" using aluminised Mylar film. So if you think that's expensive, God help you when you find the real stuff!

    See Bill's excellent report: http://www.glodark.com/cable.htm
  12. sieade245

    sieade245 Member

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    Until recently, I have been using 2x50m runs of cable in my SKY HD setup. I live in a block of flats and I was on the wrong side for the dish, hence the length of cable. I used WF125 cable and a 60 cm dish, on the Lizard in Cornwall, which is just out of the main reception area according to Sky's sat map. Recently I have moved and am now using only 5 metres of cable (much easier!), and the signal quality has only gone up by one bar. I know you are not using Sky equipment, but hopefully this will give you some idea of what you can expect.

    It was a 60 quid 100m roll from Satcure. At the moment, I'm selling both 50m lengths on Ebay (ends tomorrow). If you don't mind second hand cable, that's probably the cheapest you will find it. At the moment, its only up to 55p! Don't think I can post a direct link, but hunt around and you will find them. Hope this helps!

    Si
  13. SamRadford

    SamRadford Active Member

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    You might need the instructions for fitting the special 'F' plugs. (Easy when you know how.)
  14. Alan Mac

    Alan Mac Member

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    I don’t like heights either!

    A 30 m cable run of something like WF100 cable should be fine.
    Do not use any additional amplifier (“booster”).

    You will need to protect the cable from mechanical damage. I have used ordinary plastics garden hose-pipe with the cable threaded inside. The hose-pipe / cable can then be buried in the ground where necessary.

    I found it was difficult to thread more than about 15 m of cable into the hose-pipe so, if you do decide to use hose-pipe, you may need to use two separate lengths of hose and a plastics hose joiner. Don’t cut the satellite cable though! Keep it as one intact 30 m length.

    To prevent water etc. entering the pipe, seal the pipe ends to the cable with self-amalgamating tape. Fit a waterproofing boot over the F plug where the cable connects to the satellite “dish” LNB.


    Alan
  15. hornydragon

    hornydragon Active Member

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    40m isnt that long often far longer on commercial jobs USE foam filled Copper over copper cable Protect the cable from UV and damage with either copex (flexi conduit) or with hard conduit, use propper F plugs if possible crimped and taped/booted (i prefer self amalgam tape) a zone 2 dish rather than a mini dish (big improvement in adverse weather) and if posible rnthe cable straight into the back of the box and you should be fine. a Quality LNB will help also.
  16. SamRadford

    SamRadford Active Member

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    I left my hose pipe outside and it had split within a year. After two years it had gone white and crumbled into tiny pieces. If you bury it in the ground it will be protected from ultraviolet but not from soil microbes, moles, etc.

    Ideally, you should use the proper Alkathene conduit. It comes with couplers so you can join short lengths but keep them sealed.
  17. fernandez

    fernandez Active Member

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  18. Alan Mac

    Alan Mac Member

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    Yes, certainly use Alkathene conduit if you feel that hose-pipe is unsuitable.
    A professional installer should use conduit to be on the safe side.

    I think it depends very much though on the quality of the hose-pipe used.

    My satellite cable is 100 m long and was laid 5 years ago.
    My UHF aerial cable is 60 m long and was laid 12 years ago.
    The 80 m UHF aerial cable at our previous house was laid in 1983 (25 years ago).

    All three cables were buried (in hose-pipe) for much of their length and are still in working order.


    Alan
  19. dkleeman

    dkleeman Member

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    This is a very helpful thread. At the risk of going over old ground, I need to site a Freesat dish right at the end of my garden for it to work and with bends/routing etc. I think that the whole run will be about 70m long.

    I am concerned that fitting 4 x WF125 cables into a conduit will be quite hard as well as expensive and so I am wondering if CT100 is acceptable for this length of run. I am planning to use a zone 2 dish to boost the signal (in Surrey).

    Is there an accepted figure for the maximum length of WF100 you can use? Is it actually worth using WF125 instead? Any comments would be much appreciated.

    Daniel
  20. bob1

    bob1 Active Member

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    Your obviously going to loose signal strength whatever cable you use ,why not go for a bigger dish if you can,it will help.
  21. dkleeman

    dkleeman Member

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    Do you mean bigger than zone 2?
  22. bob1

    bob1 Active Member

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    Yes the bigger the dish will give you a better signal to start with, also some lnb's will give you a better output for a longer run of cable than normal.
  23. wod

    wod Member

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    yes i would go with 80cm to make sure the signal is best to go over that distance.
  24. =Bladerider=

    =Bladerider= Member

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    70m isnt very far.

    As a very rough guide, the different cable grade numbers give you their maximum useable length for a decent level of signal you would expect to get from the classic 60cm dish.

    So CT/WF100 is ok upto 100m
    CT125=125m
    CT167=167m

    Without going into loads of debate a rough guide to figures would be that you get about 70dB from a minidish and around 75dB from a 60cm (sorry buts its ages since I worked with dishes this small :D) and in general all the above cable length relate to a loss of around 30dB. It used to be pretty accepted that you want no less than 45dB at the receiver to ensure a decent picture, preferrably 50dB and decent bit error rates for digital.

    Now before peeps start finding this amazing - I would still recomend that you would for the benefit of precaution go up a size in dish to compensate for very poor weather, so personally I would allow an 80cm dish to begin with, or perhaps drop 25m off the length of the cable for a 60cm one. Its only recently with the heavily arc'd dishes that Sky Digital brought out that these minidishes have given acceptable signal, and even then they are marginal for alot of areas and dont offer great poor weather resitance.

    To allay fears that Im talking wizard speak, I have a 200m drum of WF167 equivalent cable that I use with an 80cm dish as a test rig for large buildings to check for encroachment from cranes and other such anomalies when we install the systems my company does, so it is easily possible to go properly long distances without amplification.

    As for the cheapest prices for cable then Alltrade is usually the cheapest, and I prefer dealing with the Watford Branch - I only use Webro cable, but they do stock cheaper alternatives. Ask to speak to Terry the manager there, tell him James from Camul recommended you try them and you may well be surprised at how cheaply you can buy the very best cable, or some of the slightly cheaper ones. We just put 3km into a building today and it costs me less than 30p/metre from memory, and there smaller amounts rates are not that much more expensive (not like double or anything silly).

    Hope this helps you guys out.

    Regards,

    James.
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  25. dkleeman

    dkleeman Member

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    Thanks Bladerider, that is enormously helpful.

    Daniel
  26. wadge

    wadge Member

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    Bladerider, I just spoke to Alltrade and mentioned you, hope that's OK.

    I am in a similar position to the OP. A run of about 45m and deciding whether to go with wf125 or wf100. I'm thinking of going with wf100 and a larger dish. Got a 1.1m motorised and a zone 2 sky dish.
  27. logiciel

    logiciel Moderator

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    He hasn't posted since last year but maybe he's still around.:)
  28. wod

    wod Member

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    45m will be fine and use a high quality lnb like the inverto black ultra, make sure there is no sharp bends in the cable run as this can affect the signal and cause losses.
  29. =Bladerider=

    =Bladerider= Member

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    Im still alive !! lol

    I just dont post much these days as Im busy rebuilding my business after poor health a couple of years ago.

    Anything sub 60m can be done in 100 with ease off a zone 2. I would never recommend the use of the small gauge "shotgun" cable that Sky use now for anything but the very shortest of runs, Webro do make a WF100 shotgun cable that one of the companies I contract for alot pioneered the use of in the UK, I think its called WT100 but again, Terry at Alltrade (moved to Hemel Hempstead now) will know the one.

    Glad to have been of help.

    J.
  30. logiciel

    logiciel Moderator

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    Welcome back then.:thumbsup:

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