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CommScope 5740 vs. 5781 RG6Q ???

Discussion in 'Technical Talk (Closed Forum)' started by Punkitup, Feb 15, 2003.

  1. Punkitup

    Punkitup AllStar/Supporter DBSTalk Gold Club

    Feb 9, 2003
    Ok so this may be an exercise in "who cares?", but just for giggles; I thought I would ask for the knowledgeable opinions of you guys on the day-to-day functional differences in these two cables when used for DBS.

    Yesterday I received 500ft of CommScope 5740 from Cable-X-Perts for $75. [minus s&h], it would appear that 5740 is a discontinued line as the official CommScope website doesn't even list it. I could have gotten 1000ft of the CommScope 5781 direct from the manufacturer for $90 [minus s&h], but to be honest I didn't need 1000ft or have the extra cash for item and additional shipping.

    So I am wondering what would have been the realized benefit anyway? I know the 5781 has a solid copper conductor verses the copper covered steel of the 5740, but there are advantages to each. I am wondering what the difference between Aluminum Braid and 3 or 4 Sided Aluminum Braid is as noted in the Spec Sheets? Also I know the 5740 has only been Sweep Tested to 1000mhz but if you extrapolate it out to 2200mhz [as is done on the spec sheet] the 5740 actually has better Loss Figures then the 5781.

    So here are links to the Manufactures Spec Sheets; have a look and tell me what you guys think is the real advantage to paying the extra dough for the 5781 would have been? Spec Sheet CommScope 5781 or Spec Sheet CommScope 5740 [adobe format].

    Peace - James/N8SBU
  2. waydwolf

    waydwolf Icon

    Feb 2, 2003
    According to the PDFs you attached, there's not a lot of difference and none you need to be worried about unless you intend to use these for laboratory grade work or wire up ten bazillion receivers which are insanely unreliable and can stand zero problems with signal to seven or eight decimal places.

    The most important parts of dealing with coaxial cabling for RF systems, specifically cable and satellite, are:

    • good shielding - ingress in messes up your reception and leakage out angers the FCC
    • good jacket without breaks - water and atmospheric contaminants eat the internals
    • good fittings - badly designed and/or applied fittings will cause ingress and/or leakage and/or water and atmospheric contamination
    • good cable run practice - no tight twists, bends, and definitely no kinks

    We are no longer talking about analog systems where the slightest signal problems were immediately apparent on your screen. Digital error correction makes many slight problems invisible to the user, up to a point, at which you get "sparklies".

    Using these two cables, with identical installation supplies and practices will not cause any errors you will notice without an oscilloscope and spectrum analyzer.

    When purity of signal becomes important is when there is intent to distribute the signal massively which thus requires amplification. Amplifiers amplify everything within the target band that they don't filter out and that means noise as well. This is why you should use a 1 meter dish or better for a several hundred apartment MDU and you only need an eighteen incher for a single family house with four sets.

    Remember, good materials and practices geared to the end result desired are all that is required to deliver service that you'll be happy with. Anything beyond that is strictly optional.
  3. Punkitup

    Punkitup AllStar/Supporter DBSTalk Gold Club

    Feb 9, 2003
    I have searched the web to no avail; I am still no closer to finding out what the "3 sided aluminum braid" and "4 sided aluminum braid" means? I know it doesn't matter, but they are terms I have never heard before and it will bug me till I find out what they mean. It may be a reference to the strand material or it may be a term that refers to Weave Angle, Number of Strand Groups or Number of Strands.

    Peace - James/N8SBU

    "Armed and Curious"

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