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HR24-500 issues, replaced with a -100 and a -200

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by mikelbeck, Oct 27, 2010.

  1. Nov 4, 2010 #61 of 121
    dsw2112

    dsw2112 Always Searching

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    I've seen some of your posts regarding grounding and agree that the concept of a "safety ground" is a poorly understood concept by most. In this context grounding the dish would be for static discharge, which alone can make a difference in regards to electrical equipment. There's also the rational that a coaxial cable is constructed to shunt interference to ground (through the exterier shielding.) If you've ever "played" with RF via coax, you'll "see" that a ground can be an extremely important aspect. I've got some first-hand experience with this (hint, look at my avatar ;))
     
  2. Nov 4, 2010 #62 of 121
    hasan

    hasan Well-Known Member

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    Precip or partical static bulld up does happen. It can be discharged through the ground provided by the shield of the coax, if the build up is not too great and the coax run is short and properly terminated at the far end.

    A safety ground (which is far better/safer than relying on the coax braid/foil) will do a much better job of reducing static discharge.

    An example of a safety ground for a dish is a short thick wire from the dish directly to a ground rod beneath the dish. One could also run a safety ground from the dish on a roof to the ground, as long as it needs to be. It would serve as a safety ground, but not much of a ground in terms of lightning mitigation, and the longer the wire, the poorer job of static discharge it will do.

    UPSs are a very, very good idea! (I have six of them on my home theater setup alone).

    All that said, I have never observed any sat box based static discharge issues in 15 years, and none of my dishes (two) are grounded. They are very low and protected from the elements. On the other hand, I can readily observe the bulid-up of precip static on my high frequency radio antennas, as well as on one high VHF/UHF antenna. The problem has a very, very clear signature:

    Noise slowly builds up to a very high level, increasing from near nothing to many dB higher (like 100 dB) and then POP, drops to zero and begins rebuilding. This happens with a VERY thoroughly grounded system...it is not reduced by the grounding system one bit.

    In summary: Safety grounds are a very good idea. They may help with minor static build-up issues. They do little for large ones, and are virtually useless for lightning induced problems.

    A very important caveat: "Properly Grounded" is a big, expensive job, not to be taken lightly or casually. A simple wire from dish to ground is not even remotely a "proper ground". It is a safety ground that may or may not ameliorate static build-up. It is still very important to have one, in terms of not getting electrocuted.:)
     
  3. Nov 4, 2010 #63 of 121
    Richierich

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    Excellent Post Hasan!!! Thanks!!! :)
     
  4. Nov 4, 2010 #64 of 121
    dsw2112

    dsw2112 Always Searching

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    A good post, but just to point out something about the above. Static dishcharge will occur in the above scenario "if" your coax is grounded. It is only grounded if a receiver, dish, or coax itself is grounded. Coax is not a ground in and of itself... So by default, if your receiver or coax is grounded, then your dish will also be grounded. Not anything remotely close to a safety ground of course, but grounded in the basic sense of being attached to an electrical ground...
     
  5. Nov 4, 2010 #65 of 121
    Richierich

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    That is what I have read in another post awhile back but as I am not privy to these things I find it interesting to read posts from those of you who are knowledgeable in this area of expertise.
     
  6. Nov 4, 2010 #66 of 121
    hasan

    hasan Well-Known Member

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    That is correct. The braid/shield is a "ground" (of sorts, lots of caveats), if (as I said) it is terminated properly at the far end. That means it is connected to the sat connector, (and by virtue of same), it is connected to the chassis ground of the sat box. From there on, it is a function of a properly wired and functioning electrical outlet as you noted. Coax in and of itself, should never be considered a proper safety ground (because when you disconnect the coax....oooops!). While it is connected, it may provide some reduction in precip static build-up.

    All of this precip/dust/partical (static build up) stuff can be very daunting. Size, shape, length and surface area of conductors all influence the potential for static build up. Reducing or eliminating its effects can be fairly easy (as with our low mounted dishes), or a real bear (my long HF antennas and high pointy VHF/UHF antennas).

    I'll give you a graphic example. When I was 16 years old, working with my first HF wire antenna (33' on each side, fed in the middle with coax). We started getting a very heavy wet snow. I kept hearing a snapping sound coming from my antenna tuner box. I disconnected the coax from the tuner, and held it about 1.5 inches from my ground rod. Every thirty-five seconds a beautiful blue-white arc would snap from the center conductor of the coax connector to the ground rod. Very impressive to a young mind!

    The snapping I was hearing before I disconnected was from the tuning capacitors (parallel plates) in the box arcing across the gap between the parallel plates (one of which was grounded). The capacitors were rated at 1500 volts...and they were arcing easily. It is no wonder, when I could make the static build up jump an inch and one-half gap, holding the coax in my hand.

    I was able to track the intensity of the snow fall by graphing the time it took to build up to a discharge. As the snow rate decreased it took longer and longer for the build-up to get to the point where it would jump the gap.

    Nothing like a spark show to pique one's interest in science.:)
     
  7. Nov 4, 2010 #67 of 121
    Richierich

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    And How Ignorant Are We As Far As Knowing And Understanding How These Things Can Affect Our Electronic Devices?

    I would say most don't have a Clue!!!
     
  8. Nov 4, 2010 #68 of 121
    hasan

    hasan Well-Known Member

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    You have taken the most effective two steps:

    1. Safety Ground

    2. UPS

    You can't do much better than this without a large investment in labor and cash, and an adequate knowledge base on DC and RF grounding. DC grounding is fairly straightforward, RF grounding is much, much more demanding, and lightning induced damage has a large RF component.

    N.B. If you have a piece of electronic equipment that you care about, put it on a UPS. It covers a myriad of other minor sins.:)
     
  9. Nov 4, 2010 #69 of 121
    Richierich

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    I have spent over $2,000 on all of my UPS Devices and alot of people would think I am crazy but I don't seem to have the Problems that others Experience because they are not Environmental Protected and Secure!!!
     
  10. Nov 4, 2010 #70 of 121
    dsw2112

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    I must say that's very impressive!
     
  11. Nov 4, 2010 #71 of 121
    Richierich

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    Very Impressive!!!
     
  12. Nov 4, 2010 #72 of 121
    hdtvfan0001

    hdtvfan0001 Well-Known Member

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    Then again...we could start a poll. :D

    In the mean time...I thought we were talking about the HR24-500 and its brethern... :eek2:
     
  13. Nov 4, 2010 #73 of 121
    mikelbeck

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    Right, back to the topic at hand...

    So should I be worried about the dish not being connected to the ground bar?
     
  14. Nov 4, 2010 #74 of 121
    hasan

    hasan Well-Known Member

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    For electrical safety it should. As far as performance goes, not so much.
     
  15. Nov 4, 2010 #75 of 121
    dsw2112

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    Regardless of what side of the fence you're on (in regards to the grounding issue) it won't hurt, and I would definitely recommend it.
     
  16. Nov 4, 2010 #76 of 121
    mikelbeck

    mikelbeck AllStar

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    Ok, good.

    As for the tech saying that voltage on the ground line would cause my receivers to lock up - is there anything to that? It a little over 1 volt.
     
  17. Nov 4, 2010 #77 of 121
    Steve

    Steve Well-Known Member

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    Lower...
    The thread starter's issue became a grounding question at post #54.
     
  18. Nov 4, 2010 #78 of 121
    Steve

    Steve Well-Known Member

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    I'm now remembering that the "specialist" at DirecTV who told me my dish did NOT need to be grounded also told me that grounding it unnecessarily could actually cause a problem. Whether or not it's the problem you're seeing, I have no idea.

    I remember this because I did ask him "why not ground it anyway, to err on the side of caution?"
     
  19. Nov 4, 2010 #79 of 121
    dsw2112

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    I missed that earlier, what'd you use as the reference point to check the ground?
     
  20. Nov 4, 2010 #80 of 121
    mikelbeck

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    I tried a bunch of different things - the ground rod, the frame of the A/C compressor (sits on a patch of concrete), the metal conduit that the A/C wiring runs through... I got the same reading using all of them. When the green ground wire was connected from the grounding block to the ground rod there was a little over 1 volt on the green wire and the ground block. When I disconnected the green wire from the block there was about 12 volts on the grounding block.
     

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