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Max coax run length for MRV

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by snowtrooper1966, Aug 27, 2010.

  1. snowtrooper1966

    snowtrooper1966 Cool Member

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    May 15, 2010
    Greetings!
    Had installer come out yesterday for my MRV install. Besides having three trucks on site with one guy being a supervisor, they were really perplexed as to location for dish. They finally decided I could put it in a particular spot, but that I would need to level it out (on about a 15 degree incline), and were warning me that the 75 foot run from the dish to the main TV/HR24 was at the limit of the powered SWiM, and the additional 25 feet to the second TV was likely going to produce signal issues for the H24 there...
     
  2. dsw2112

    dsw2112 Always Searching

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    Simply not true. With two receivers you'll get a SWMLnb so the power only flows from the PI to the dish. If the PI is placed at the Tv (75 foot run) that will work just fine (this wouldn't even be a problem on a legacy setup.) With SWM the distance can be much longer. The actual satellite signal can travel much further on almost any type of coax (think hundreds of feet) so the additional 25 feet to the second Tv is irrelevant...

    Any digging/trenching aside, this is a no-braier and an easy install with SWM...
     
  3. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    "Max length" has a lot to do with splitters and the number of other drops.
    A single line to one receiver has been tested out over 300', but at the same time this would be greatly reduced if an 8-way splitter was used.
    I've got about 100' of coax and use a 2-way & a 4-way splitter, which all works fine, but seems also to be close to the max loss for the system, before things start to degrade, and/or eat into the system reserve.
     
  4. dsw2112

    dsw2112 Always Searching

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    VOS brings up a good point as I forgot the propensity for installers to use 8 way splitters (even for a 2 box install.) Keeping the splitter as small as necessary will help tremendously.
     
  5. snowtrooper1966

    snowtrooper1966 Cool Member

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    May 15, 2010
    That's what I though as well, just needed a second opinion, and new he experts here would give me some good info....
    Just moved and started a new accont to be sure I would be getting a HR24 based MRV setup. They came Monday with the wrong equipment (install workorder said nothng about MRV, and they only brought standard def for 2nd TV, resheduled for yestrday and got the runaround described above. Seems like they don't wanna do the install.....
    Thought it was fairly simple install, 2 TVs, one 2 way splitter.....
     
  6. TomCat

    TomCat Broadcast Engineer

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    I don't know much about SWM, but there are only four ways a broadband RF distribution system can use longer cable lengths (than conventional) that immediately come to mind:

    1) more amplification

    2) tuners with greater sensitivity

    3) frequency conversion to a lower band

    4) bigger coax, such as RG-11

    or some combination of the above. 1 is likely; 2 is unlikely (since the tuners are probably the same); 3 is implied (you can't multiplex signals at the same frequency, meaning one or more polarities must be converted to either a higher or lower band, and lower is the only way to reduce cable loss); and 4 is impractical.

    So how does SWM actually accomplish this "hundreds of feet" task?
     
  7. texasbrit

    texasbrit Well-Known Member

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    Tomcat - (1) and (3). The SWM systems have AGC (up to 15db of gain) which regular systems don't have. And the system uses considerably lower frequencies.
     
  8. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    The frequency changes wouldn't be "considerably lower", "IMO" as they still could be 1800 MHz if using the last/highest SWM channel.
    Before SWiM the bands are 250-750, 950-1450, and 1650-2150 [used now only for some locals].
    SWiM outputs are 974-1790.

    TomCat
    SWiM is a different system than a switched/dedicated drop legacy system.

    As posted, it has an AGC on the output to attenuate a -15 dBm input to -30 dBm, and amplify a -45 dBm input to -30 dBm.
    Receiver inputs want to be about -54 dBm, so this gives about 24 dB of system loss [splitters/cable] before the receiver has any problem.
     
  9. dsw2112

    dsw2112 Always Searching

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    Also, the biggest "problem" on a legacy system is related to the receiver providing the DC. The RF could always travel a lengthy distance, but the DC voltage drop was a limiting factor. This is why polarity lockers worked well on such a system...
     
  10. TomCat

    TomCat Broadcast Engineer

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    All great answers. Thanks, I knew I could count on you guys (and we all stayed on topic.:))
     
  11. goblazers_6

    goblazers_6 AllStar

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    Apr 20, 2009
    150' is what we try to keep the MAX run under (i.e. LNB to furthest IRD).
     
  12. snowtrooper1966

    snowtrooper1966 Cool Member

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    May 15, 2010
    Thanks, I'm well under the 150' to the furthest reciever (IRD?).
    Wonder why they were giving me such a hard time.....
     
  13. texasbrit

    texasbrit Well-Known Member

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    VOS - the higher frequency band (up to 2150) used to be just for HD locals but the DirecTV12 satellite (103ca) now uses that frequency band for national HD.
     
  14. Mike Bertelson

    Mike Bertelson 6EQUJ5 WOW! Staff Member Super Moderator DBSTalk Club

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    I have 75' run of RG59 on one of my receivers with no issues.

    Mike
     
  15. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    Thanks, I didn't realize anything but Spaceways were using Ka-Hi. Nothing ever stays static. :lol:
     
  16. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    The recommended max between the LNBs and the SWiM is 45'. This was why I linked to an amp in my first post, guessing you weren't going to mount the SWiM on the tower.
    Ideally you don't want a lot of loss between the LNB & the SWiM, as this will eat into the AGC range and cause less reduction in things like rainfade.
     
  17. dsw2112

    dsw2112 Always Searching

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    I'm not sure how many receivers the OP has, but in this case the SWM & LNB are likely one and the same (SWMLnb.)
     
  18. snowtrooper1966

    snowtrooper1966 Cool Member

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    May 15, 2010
    Just to clarify, this will be a new MRV install, with the dish/LNB 75' away from the first HR24. Not sure if PI is used for the 24 series. There SHOULD only be a 2 way splitter where the coax lands outside the wall for the HR24, and from there, another 20' of coax to the only other box, an H24.
     
  19. dsw2112

    dsw2112 Always Searching

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    This will be a SWMLnb then. If you requested the ICK (internet connection kit) then the installer will need to utilize something larger than the 2-way splitter to "inject" the internet (or a second 2-way.)

    PI's are always necessary for any SWM sytem regardless of the receivers utilized. As mentioned earlier this install is straightforward and the SWM system will perform well with the specs you provided.
     
  20. snowtrooper1966

    snowtrooper1966 Cool Member

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    May 15, 2010
    Did not order the ICK, what's the benefit of that VS just connecting my own cat5 to the HR24?
     

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