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Have some questions re: antenna install

Discussion in 'Amateur Radio Antennas' started by KB9NHA, Mar 4, 2010.

  1. KB9NHA

    KB9NHA
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    I just got my new Comet GP-9 dual band base antenna that I've ordered recently. I've done some search on the web regarding the best dual band base antenna I can get particulary the Diamond X500HNA & ultimately settled with this antenna than the other one by Diamond based on what I've read at eham. This is also cheaper than the Diamond & less prone to getting wet inside & getting high SWR reading. I'm hoping to install this antenna this weekend. This will be my first time installing a Ham radio base antenna so I got some questions.

    I was planning to install this antenna at the rooftop of my house but changed my plan after I got a response from the local village people. Inorder for me to install this antenna I must get a permit for it. I must get a professional electrician check the plan, a utility personnel to check for buried electrical lines & a professional antenna installer to install the antenna as well as to make sure that the roof can support the weight of it.



    My plan now is to install it with the mast at the side of the house. The base of the mast well be resting about 9 feet above the ground. From the base, there's about 11 feet of height for the mast to level with the rooftop. My questions are:

    1. What's the minimum height of the mast that I can put starting at the rooftop level? I'm worried that if the mast is too short, this will cause signal interference on electronic equipments (telephone, tv, router, etc.) not just inside my house but the surrounding neighborhood. I'm not so familiar with antenna's radiation pattern but the gain is pretty high, enough for me to worry about signal interference.

    2. I bought a lightning arrester (just in case). Do I need to install it for just a VHF/UHF FM base antenna. The instruction manual for the antenna says that it's equipped with lightning protection already. If so, how do I install the lightning arrester? Do I need to just screw the lightning arrester (connected to the antenna) near the mast & run a ground wire & connect it to a metal rod buried on the ground? I have no idea on ground wires, what kind of ground wire will I use?

    3. Any idea on what kind of mast to use? I been to Home Depot earlier today to check for ideal mast to use. I saw a metal pipe (very heavy), a PVC pipe (will bend) & aluminum pipe (very wide). I saw an aluminum mast (ideal size) from another home improvement store that can be pieced together to make it longer. Any idea if this kind of mask can survive in windy weather? I lived about 25 miles northwest of Chicago. At times we have very strong winds around the area.
     

  2. Nightshade

    Nightshade
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    For CB radio use the height limit is 60 ft. so go with that to be safe.

    Here is a link that will give you all sorts of good info..........

    Amateur Radio Antenna Projects

    As to a pole to mount your antenna...........
    You don't need just a pole you need a proper antenna MAST. Anything less than a mast designed to carry/support antennas will not do safely. Google antenna mast to see what I mean.

    A lightening arrestor is a good thing but nothing will take a direct hit so always make it a habit to unplug & unhook your radios from power and your antenna during a storm or when you're not using them . Cheap safe insurance.
     
  3. Digger

    Digger
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    What in the name of God kind of Nazi housing organization runs the neighborhood that you live in? Sounds like total BS to me, not on your part but on their's. Do they also tell you what time you can take a leak? :whistle:
     
  4. W5LZ

    W5LZ
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    Crotchety Old Bastard

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    The quick-n-dirty answer is to mount it as high as possible, however you can do that. Higher is better for VHF/UHF antennas (any antenna but VHF/UHF especially). I would imagine that as long as the antenna isn't extremely 'visible' it should pass 'inspection'. If you have to do it that way, that antenna will also work at ground level. Not as well as if it were at 100 feet, but...
    - 'Doc

    (It's too late to do much about antenna restrictions -after- you signed the contract. Sorry 'bout that.)
     
  5. KB9NHA

    KB9NHA
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    LOL... I'm from Arlington Heights, IL. Yup, you're right Digger, it's kinda extreme what they're doing.

    Anyway, I returned the Comet GP-9 antenna today. I'm not comfortable putting it up even at the side of the house. It's very long (about 17 feet) & I noticed that when 1 put its 2 sections together & placed it up it bends when I moved it. With the entire 3 sections put together, the antenna can't stand a strong wind typical of Windy City.

    I decided to purchase a Diamond X200A antenna instead. Hopefully it get delivered by Wednesday next week. The antenna doesn't have the optimal gain you'll get with Comet GP-9 but its a lot shorter (about 8 feet) & less visible. The gain is also not bad (6.0 dB on VHF & 8.0 dB on UHF).

    I saw this mounting kit for satellite disks & tv antenna at a local home improvement store in my area called Commdeck. I got a picture of it below...

    [​IMG]

    [​IMG]

    I read the specs of this mounting kit & it says it can support a mast not exceeding 6 feet. I got a 4 feet aluminum mask. This should be OK. I got almost everything except for the antenna. Can't wait to get on air.

    Nightshade, you're right. There's no such thing as total lightning protection. I read about it yesterday. Even if you have the best lightning arrester out there, it's always good to turn off your radio & disconnect its power source when there's a potential thunderstorm.
     
    #5 KB9NHA, Mar 6, 2010
    Last edited: Mar 6, 2010
  6. Nightshade

    Nightshade
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    WHOA!!!!! That mount you're looking at will not be strong enough to support a long (or larger than the photo antenna) in any sort of wind. Better to get a tripod mount then get either a mast or a galvanized 1 1/2>2" water pipe (NO joint so the max is 10' ) That is what I used for 20 years until I switched over to a small tower.

    http://www.solidsignal.com/cview.asp?d=over-the-air-tv-antennas-supplies&c=Mounting Supplies&mc=03
     
  7. KB9NHA

    KB9NHA
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    I surely will consider your advice Nightshade. I saw a similar tripod that you mentioned on that link at the place where I bought that antenna install kit. I agree, it's very sturdy than the kit that I have now. I might check on it again tomorrow & probably rethink what's the best for me to install.
     
  8. W5LZ

    W5LZ
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    Crotchety Old Bastard

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    Depending on the pitch of your roof and how 'tall' it is above the eaves, mounting that antenna so the base is about even with the eaves of the roof will probably be your best bet. That would at least keep the antenna from being seen form the street (if the roof is 'tall' enough). One method of doing that is by ground mounting a mast next to the side of the house. Would that make the antenna work as well as if it were mounted higher? Of course not, but you'd -have- an antenna, and it really wouldn't be all that bad.
    I have one of the dual band Comet antenna, the GP-1 I think, at about 20 feet. Also a 'J'-pole at about 5 - 10 feet +/- some. Not a great difference between them with local stuff. So a roughly 10 foot difference in mounting height for your antenna should work out about the same. Not the 'best', but not bad either.
    Good luck.
    - 'Doc
     
  9. KB9NHA

    KB9NHA
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    I ruled out installing the antenna with the base of the mast on the ground to side coz the roof it's kinda high (about 25 feet or slightly higher). This is also the reason why I'm considering paying someone (doesn't have to be a professional) to install the antenna install kit or tripod coz I'm afraid of high elevation. The highest I climbed is the top of the garage roof (yesterday when I was checking a best place to put the antenna). If I could mount the antenna at the top of the roof even if I only use shorter a mast I think I still be OK with my antenna set up.
     
  10. Nightshade

    Nightshade
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    I, too, don't like heights so when I put up my tripod/pipe for the antenna I set the tripod dead straddle of the ridge of the roof. Using 9/16 lag screws and a large washer I screwed the tripod to the roof closing with silicon caulk over the screw heads to seal.

    I wondered if I needed to guy the pipe but since my old house has lost of wood everywhere I got a really good bite into the thick roof boards (no plywood there!). That is how the antenna stayed for next 20+ years until my tower went up spring of 2009.

    With the antenna mounted this way I was able to send (CB) and receive a well as could be expected in the valley I live in. In total the tip of the antenna (vertical) was 62 ft above grade with my tower now being up 75 ft.
     
  11. kd-5-bgt

    kd-5-bgt
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    Guying any mast mounted with the mounts shown above is a good idea...and if guying the mast you can go somewhat higher than what the book says you can,since the base mount will just be holding the base in place instead of trying to support the entire wind load of the mast and antenna,just use common sence for guying the mast and you should be fine....I would be willing to say that a 20 foot mast guyed at the 18 foot level will not give you any problems

    and another good idea would be to go into attic and nail or screw a 2 by 12 flat between the rafters against the roof decking to support the base and for the screws to run through.....put screws or nails through the rafters into the ends of the 2 by 12..I would say 3 nails or screws per side will hold the 2 by 12 without any problems...The fewer holes in the roof the better off you will be...and just be sure the 2 by 12 is tight against the under side of the roof deck....if the rafters are in 16 inch centers the 2 by 12 length will be about 14 1/2 inches and if the rafters are on 2 foot centers the 2 by 12 length will be about 22 1/2 inches

    be sure to use a good quality caulking to seal up any leak points that the lag screws might cause..(use some 2 1/2 inch screws with at least a 1/4 inch shaft ..tighten them snug but do not over tighten) ....use a urethane based caulking such as NP-1...that is by far the best caulking that I have ever used,it will never dry up or wash out if you should get rain shortly after doing the install ...and that NP-1 will stick...if it gets a good bond it will NOT ever turn loose,it is well worth the extra few dollars to use over any silicone or acrylic based caulking

    I am a carpenter and roofer by trade and that is what I would do for supporting the base mount for mast that I am seeing posted in this thread.The 2 by 12 will insure that the lag screws will not pull back through the roof decking or cause the decking between the rafters to ever sag due to any extra weight that the antenna mast or base plate will have
     
  12. furcifer

    furcifer
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    I do know this post is over a year old, but I felt I needed to add my part to this for clarification for other future users who might get the wrong information.

    The mount that is in the picture IS strong enough for his antenna.
    I have 2 of those mounts.
    They hold up my Comet GP-3 antenna that is 5'11" tall and a marine band Shakespeare antenna that is 4'10" tall. I have one mounted on one end of my roof and I have another on the opposite end.
    They both only hold one antenna each. Also, they DO hold up in high winds (from my experience). They survived the high winds/F3 tornadoes that swept through the St Louis area on December 31st, 2010, and they held up on Feb. 28th, 2011 when an F2 tornando passed within 2/10ths of a mile from my house. So from a person who has actual experience using these mounts in high wind situations, these mounts are pretty darn strong.
     

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