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Tower Installation

Discussion in 'DIRECTV Installation/MDU Discussion' started by babzog, Jul 14, 2008.

  1. babzog

    babzog Godfather

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    Sep 19, 2006
    Hey folks,

    Been soaking up some answers and picking up some great tips - what an awesome site for all things sat related!

    As I mentioned in other posts, I'm re-roofing the house with steel and taking everything down that's up there - wireless radio (internet), an old chimney chase, satellite gear, etc.

    I'm building a 50' freestanding tower on which to mount all this gear. I intend to run conduit for the 100' or so to the service entrance of the house. I also intend to properly ground everything. There will be about 6 coax lines running through the conduit to the house for all services.

    I'll initially mount my old round dish but intend to mount a slimline there, probably this fall. Dish will probably be 10' or so off the ground to clear the treeline.

    I've been reading some of the ham radio sites for ideas on how those guys ground their towers (seems like folks prefer each tower leg grounded to its own rod).

    My questions then, based on the above:

    1. As the tower is grounded to its own rods, does the dish need to be separately grounded, or is a steel dish being bolted to a grounded steel tower sufficient grounding?

    2. If I must separately ground the dish, can I ground it to the tower ground? Or...

    3. Do I need to ground the dish to the house ground? If so, is twin coax with built-in ground wire the best for this job?

    4. Given the tower's distance from the house, do I need to connect my tower ground rods to the house ground?

    5. Do I need to ground the coax separately at the base of the tower?

    6. For the Slimline installation. It'll be mounted at the corner of the tower (I positioned the tower to use a corner for the dish so there'll be max room to swing it). Will I need additional bracing for this dish on the tower or will the supplied mast be sufficient?

    I know it's a lot of Q's, but I appreciate any advice you can offer!

    Cheers!
    Jon
     
  2. Mertzen

    Mertzen Hall Of Fame

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    Dec 8, 2006
    How deep does the tower sit in the ground? I think it needs to be at least 8-10 ft to be automatically grounded if I'm correct.

    I'd still run 4 wires from the dish to the base and put a ground block to make maintenance easier.
     
  3. Scott in FL

    Scott in FL Godfather

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    Mar 18, 2008
    Hi Jon,
    Your installation sounds similar to a 60' ham radio tower I put up many years ago. The NFPA publication is no longer free, but you can get a lot of good advice from these two articles:
    http://www.arrl.org/tis/info/pdf/109481.pdf
    http://www.arrl.org/tis/info/pdf/129445.pdf

    When I put up my tower I went down to city hall and spoke with them about codes, etc. They weren't very knowledgeable about antennas, lightning protection and grounding, but they did come out to inspect my work and made sure it complied with their codes. As you're putting up a big tower, don't skip this step. You will have large surges induced into your tower and you might suffer some damage. Do it legally.

    If you mount the dish on the tower, I would run a short ground strap from the dish to the tower. Don't rely on the mounting hardware.

    You should also run straps across the tower sections at each leg.

    Ground each leg, using a ring as describe in the articles. Ground the coax shields at the bottom of the tower and where they enter the house. As far as tying your antenna ground and house grounds together, I can tell you what lightning protection theory says (you should, to prevent side flashes) but this is getting into your local code department. Ask them. Hopefully you will find someone who knows antenna grounding and can assist you.
     
  4. curt8403

    curt8403 Hall Of Fame

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    Dec 27, 2007

    lights. flashing red lights will be needed on your tower
     
  5. babzog

    babzog Godfather

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    Sep 19, 2006
    Only at Christmas. :) Great idea! I've got a few strings of LED lights.. wonder if I should run some power out to the tower? Call it the Tower of Power? :D

    Lights are not required for a tower of 50', plus up to 10' mast. I think the min height for lights is 200'.
     
  6. curt8403

    curt8403 Hall Of Fame

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    Dec 27, 2007
    just do not use blue lights, or planes will mistake it for a landing beacon
     
  7. babzog

    babzog Godfather

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    Sep 19, 2006
    Hi,

    Thank you for your good advice. My neighbor is a tower guy and will be helping me assemble it... he should have a good handle on the minimums required.

    What kind of signal loss can I expect through 130" odd feet of coax that's split across 2 grounding blocks (and optionally a wb68 or wb616 switch)?

    On the grounding issue with the tower. Part 2 of the doc you referenced mentions:

    If I understand this correctly, they are referring to, when they mention "bulkhead panel", a copper plate used to mount the grounding blocks, etc which is itself grounded.

    My proposed path for the coax conduit places the box (housing the grounding blocks... not exactly a copper plate) right beside the electrical meter, at the base of which, is a power company installed grounding rod. The phone, meter, inside service panel are all connected to this rod.

    The inside panel is also connected to a ground rod right underneath it and also to a wire which runs down the well.

    If I ground the box housing the grounding blocks to the ground rod underneath the electrical service entry and also connect the tower grounding ring to that rod, then does that conflict with this excerpt from the same article:

    The highlighted portion is what I wanted to clarify. Aren't the ground rods at the tower used for lightning protection and thus should be separate from the utility ground? If so, then I'm puzzled since I thought that, from reading here, that all grounds should be bonded together (and this suggests otherwise). I don't mind rerouting the planned entry for the coax since the trench isn't yet dug.... might as well get the planning right before putting the shovel in the ground. :)

    Diagram attached showing what I am proposing.

    Thanks so much for your thoughts!

    Jon

    [​IMG]
     
  8. babzog

    babzog Godfather

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    Sep 19, 2006
    One other Q... easy one. Suggested conduit size. I've been pricing 2" and 1 1/4". I can save over $100 by going with the smaller size but don't want to shoot myself in the foot, so to speak by going too small. I'll have 6 (and certainly no more than 7 if I ever expand down the road) runs of RG6 through the conduit.
     
  9. K4SMX

    K4SMX Hall Of Fame

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    May 19, 2007
    1 1/4 should be plenty big. Buy a bottle of Ideal "ClearGlide" at the home improvement store. Very slippery stuff.

    I'm more concerned with your dish mount plans. You can hang an SD dish on just about anything. But for the 5 LNB Ka/Ku dish, it would be much better to get a piece of quarter-inch aluminum plate and U-bolt it at each corner across two tower legs. Then attach the foot of the mounting plate for the dish arm to the aluminum plate. Because of the stand-off distance of the mast arm, you should still have plenty of swivel room for the proper AZ orientation of the dish.

    There's a member photo of that exact mounting scheme in a thread here somewhere, but I can't find it. I believe he also had a big OTA antenna on the top of the tower. Maybe that member or someone else could dig up that photo and re-post it. It was a first-class tower installation.
     
  10. Scott in FL

    Scott in FL Godfather

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    Mar 18, 2008
    Hi Jon,

    Belden 1829BC has a rated loss of 7.8 dB per 100' at 1450 MHz. So 130' will have a loss of just over 10 dB. Add 1 dB for the ground blocks, and the total comes up to around 11 dB (I have no idea what the loss through a switch would be). There are some very knowledgeable installers who hang out here that might be willing to tell you the implications of such a long cable run and that much loss. I can tell you that an OTA tv antenna will require a pre-amp at the antenna.

    Your understanding of a bulkhead panel is correct (this is the way hams like to do it), and your metal box will be fine. The reasoning behind separating ground rods by at least 6' is to lower the impedance to ground. If you're familiar with parallel resistance then you know that connecting two equal resistors in parallel cuts the total resistance in half. Three parallel resistors cuts the total in third, and so on. So tying multiple ground rods together just keeps lowering the impedance to ground (which is very desirable), but the ground rods must be separated by at least 6 feet.

    All grounds should be bonded together. That's why the article states: "All grounding media at the home must be bonded together." But, your local codes now take precedence. When I installed my tower and ground system I was not allowed to connect my tower ground to the utility service ground. But the inspector had no problem with me tying my house's copper water pipe system to my tower ground, which effectively ties the two ground systems together (in my case, the cold water supply ran right past my circuit breaker box where it was connected to the utility ground, and 10 feet further that same copper pipe ran past my bulkhead panel where I connected my tower ground).

    Because your tower is located so far from the house your's is a different case. You should really take your drawing down to your local city hall and start asking them questions. With a 50' tower, this is really a necessary first step.
     
  11. SledDog

    SledDog Icon

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    May 5, 2007
    It will depend on how close you are to any airport, landingstrip, etc....

    Here's the info for the US from 14 CFR Part 77:

    Who Must File?

    ยง 77.13 - Any person/organization who intends to sponsor any of the following construction or alterations must notify the Administrator of the FAA.

    Any construction or alteration exceeding 200 ft above ground level

    Any construction or alteration within 20,000 ft of a public use or military airport which exceeds a 100:1 surface from any point on the runway of each airport with at least one runway more than 3,200 ft.

    within 10,000 ft of a public use or military airport which exceeds a 50:1 surface from any point on the runway of each airport with its longest runway no more than 3,200 ft.

    within 5,000 ft of a public use heliport which exceeds a 25:1 surface
    Any highway, railroad or other traverse way whose prescribed adjusted height would exceed that above noted standards

    When requested by the FAA

    Any construction or alteration located on a public use airport or heliport regardless of height or location

    Persons failing to comply with the provisions of FAR Part 77 are subject to Civil Penalty under Section 902 of the Federal Aviation Act of 1958, as amended and pursuant to 49 U.S.C. Section 46301(a).


    Here's the info for Canada from Standard 621.19 - Standards Obstruction Markings Chapter 2, section 2.2:

    2.2 Obstructions Requiring Marking and/or Lighting
    Unless otherwise provided for in these standards, the following obstructions should be marked and/or lighted in accordance with the standards specified therein:

    (a) any obstruction penetrating an airport Obstacle Limitation Surface as specified in the Aerodrome Standards and Recommended Practices Manual - TP 312;

    (b) any obstruction greater than 90 m (300 feet) AGL within 2 nautical miles of the imaginary centre line of a recognised VFR route such as, but not limited to, a valley, a railroad, a transmission line, a pipeline, a river or a highway;

    (c) any permanent catenary wire crossing where any portion of the wires or supporting structures exceed 90 m (300 feet) AGL;

    (d) any obstructions greater than 150 m (500 feet) AGL; and

    (e) any other obstruction to air navigation that is assessed as a likely hazard to aviation safety in accordance with paragraph 2.3.1(a).

    2.3.1 Purpose of Aeronautical Evaluations

    Aeronautical Evaluations are used by the Minister:

    (a) to determine, for the purposes of section 2.2, whether or not it is likely that an obstruction to air navigation is a likely hazard to aviation safety; or

    (b) where expressly provided for in these standards, to specify alternative modes of complying with the obstacle marking and lighting standards while ensuring that the visibility requirement set out in section 2.1 is met.

    2.1 Purpose of Standards

    The purpose of obstruction marking and lighting is to provide an effective means of indicating the presence of likely hazards to aviation safety.

    More specifically, the marking and lighting standards are aimed at ensuring that an obstruction to air navigation remains visible at a range sufficient to permit a pilot to take appropriate action in order to avoid the obstruction by not less than 305 m (1,000 feet) vertically within a horizontal radius of 610 m (2,000 feet) from the obstruction.
     
  12. Christopher Gould

    Christopher Gould Icon

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    Jan 14, 2007
    you said u wanted to mount it on the corner, but my i mount mine like this.

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
  13. K4SMX

    K4SMX Hall Of Fame

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    May 19, 2007
    Thanks, Christopher. You're the guy with the photos I was trying to find. Rock solid installation. I wouldn't want to stumble into it in the dark!
     
  14. brant

    brant Icon

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    Jul 6, 2008
    I would use 1 1/2" RNMC minimum given the distance (assuming 180 deg of bend) for 6 cables.

    You need to run a #6 AWG ground from your antenna to the grounding electrode at your service because the coax is a parallel grounding path.


    The NFPA codes are free, and you can read them HERE. NFPA 70 is the nat'l elec code. Chapter 8 covers communications antennas; most of the grounding stuff is in 820. Give it a read.
     
  15. Scott in FL

    Scott in FL Godfather

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    Mar 18, 2008
    But they're not free. When you click on NFPA 70 you only get the abstract. The code costs $67.50. NFPA 780 is the one you really want... member's price is $34.20.

    Check with your local folks before tying your antenna ground system to your service ground!!
     
  16. brant

    brant Icon

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    Jul 6, 2008
    When you click the link of the code book you want, scroll down and there is an option to open and read the code book in its entirety. The link says "click here to view the xxxx edition of the document".

    ---- i just went to check, looks like they've changed the format a bit. You'll have to click a link that says 'visitor" when trying to view it, enter your e-mail and create a password. I'm not sure how many times you can view it; it wasn't like this two months ago. That's something new.

    780 is for lighting protection; read article 800 of nfpa 70 concerning the installation of the tower itself.

    You must ground the tower to the service grounding electrode w/ minimum #6 because of the parallel path issue; that is in the code book (i don't have my book in front of me right now or i'd cite you the exact code - its 820. something). The tower has to be grounded to the service of the building it serves.
     
  17. Scott in FL

    Scott in FL Godfather

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    Mar 18, 2008
    Thanks brant. I'll give it a try. This is a great source of information, and all the better if it's free.

    The reason for my comment about not tying the tower ground to the electrical service ground was because I was told not to by my local inspector. My tower is right next to the house, and he OK'd another way to tie the two systems together. With a tower 130 feet away I'm not sure what the best approach would be, but the inspector may have a problem with tying into the service ground. And with a 50' tower, I think it's best to do it legally.
     
  18. brant

    brant Icon

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    Jul 6, 2008

    I would ask for an explanation from the inspector as to why he won't allow you to tie them together. Make sure he knows about the coax running from your house to the tower. I would also get a signed letter from him in writing stating that he wouldn't let you tie the two together, just in-case you need it for the insurance company one day (God forbid). Electricity looks for the path of least resistance back to its source; if your tower is not tied to the service and becomes that path, then any fault current on the system is going to travel through that coax (and whatever is attached to it) out to the tower. I saw this happen on an installation once where the grounding block was attached to its own ground rod (not tied to the service) and became the grounding electrode for the entire electrical system. The GEC at the service had inadvertently been detached from the rod and the TV's were routinely getting fried.


    edit--- i just realized you said they were tied together another way. through the water pipes? that'll work.
     
  19. Scott in FL

    Scott in FL Godfather

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    Mar 18, 2008
    In my case I ran #6 cable from the tower to a bulkhead panel where the coax lines also terminated. Then I tied the bulkhead panel to the copper cold water supply pipe running past the bulkhead panel inside the house. 10' away that same copper pipe was tied to the electrical service ground. So in effect both systems were tied together, but he did not want me to connect my tower ground system to the service ground rod. That's what I meant by saying he OK'd another method to tie the two systems together.

    My tower ground system consists of three 8' ground rods, each separated 6' apart, connected by a ring using #6 cable. Each leg of the tower was connected to the ring. Then the tower was connected to the bulkhead panel using #6.

    This was all back in 1986 so hopefully I'm OK.
     
  20. brant

    brant Icon

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    Jul 6, 2008
    you're fine. the #6 doesn't have to be physically attached to the rod; just bonded to the conductor that is going to the rod.
     

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