mag mount on a house roof?

KC1MZX

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hi, kind of new to this place.

I've been talking a lot to my parents about mounting a mag mount antenna on the roof of our house by drilling in a metal plate. meanwhile, they're skeptical about the lightning threat, but I'm more wondering about how well this would work and if it actually would be grounded?

any response helps

many thanks
 

mmckenna

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I've been talking a lot to my parents about mounting a mag mount antenna on the roof of our house by drilling in a metal plate. meanwhile, they're skeptical about the lightning threat, but I'm more wondering about how well this would work and if it actually would be grounded?
Would it work? Yes. But there's a lot of details that would be tacked on to that.
The sheet metal would need to be at least 1/4 wave length radiating out from the base, so for 2 meter VHF, 19" in all directions, or 38" across.
Then there's the issue with what grade and how long the coaxial cable would be. Magnetic mounts are usually intended for mobile use, and will have a short length of RG-58 coaxial cable. If you can reach your radio with 10-15 feet of cable, it's probably going to be OK. Much longer than that, and feed line losses become an issue. You would want higher grade coax for anything longer.

"Drilling in a metal plate" raises some questions. Are you talking about screwing down a piece of sheet metal onto the roof and placing the magnetic mount in the middle? That would be fine, however a couple of things to think about:
1. Make sure the screws do not pierce the roofing material all the way. A leaky roof will reduce your chances of getting to keep an antenna on the roof.
2. Sheet metal that has enough steel in it to hold a magnet runs the risk of rusting. that rusting will lead to rust streaks coming off the roof. Might be fine if it's not visible from the street.

Lightning is always a threat, doesn't matter if there is an antenna on your roof or not. But sure, putting an antenna on the roof has some risks. It doesn't even require a direct lightning strike, a nearby strike can induce a lot of energy into the antenna and cable. That can damage your radio, start a fire, etc. Using a proper lightning suppressor is required by the National Electric Code. So is properly grounding the antenna. That's not impossible to do, but it's not cheap, either.
Yeah, some hobbyists skip the grounding and ignore the code and usually their houses don't burn down.

It would not be grounded. Magnetic mounts don't necessarily ground through the mount. It relies on capacitive coupling to work. That's fine for RF, but it's not the DC ground that's required by code. The sheet metal may not be grounded that way.
Depending on the radio and how it's powered, it -may- find a path to ground through the coaxial, to the radio, to the power supply and into the home electrical ground. A lightning strike finding a path through the coax, through the radio, through the power supply and into your home is going to cause a lot of damage.

I know, not what you wanted to hear, but doing this sort of stuff correctly is something you can do, it just takes some money and some work. Mounting an antenna on a house is a big step, and as always it depends on the person that owns the house. Even when you own the house, the spouse can often over rule you.

A good option might be to set up a temporary antenna mast that you can put up and take down as you need it. There's a lot of people that do that when camping, and it can work pretty well. Only caution in a residential environment is making sure nothing ever comes close to power lines. That'll do worse things than damage your radio or burn your house down.
 

KC1MZX

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doctordialtone

im trying to use 2 meter and 70 cm
this is for two way radio
a kg-uv920
 

KC1MZX

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so I'll probably end up getting a higher grade of coax, as the distance to the area where I'd place the plate and antenna would be more than 15 feet just a couple of questions. 1. how should I go about securing the plate if I wasn't going to use screws/bolts, and what metal would work best. apart from that yes, I'm basically putting a mobile antenna in the center of a metal plate on my roof. 2 how should I go about grounding said metal plate? I'm quite new to this whole concept of setting up antennas and base stations, so I apologize if I sound like I'm just asking stupid questions.
 

KC1MZX

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side note: the reason im asking is so that i can hopefully get a working base station soon
 

KC1MZX

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You would be much better off mounting a base antenna on a mast than trying to use a mobile mount.

Is there some particular reason you want to use a mobile antenna?
it seems to be a bit simpler, and less of a lightning hazard. and I want to mount it on my roof
 

weathermedic

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How about putting a magnetic antenna on a window air conditioner (if you have one) Not the best setup, but it may give you an idea on how your rx/tx would work.
 

Bob1955

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hi, kind of new to this place.

I've been talking a lot to my parents about mounting a mag mount antenna on the roof of our house by drilling in a metal plate. meanwhile, they're skeptical about the lightning threat, but I'm more wondering about how well this would work and if it actually would be grounded?

any response helps

many thanks
KC1MZX-Buy a magnetic mount scanner antenna like a Hustler all band scanner antenna(BNC)(SMCA) and if you have a window air conditioner, that will work better. If not, then forget about my suggestion. I used that before I moved here. We have wall mounted a/c comob heat that are ductless in this brand new building and NO outside antennas allowed, not even on a terrace either.
Hope this helps you out.
 

KC1MZX

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How about putting a magnetic antenna on a window air conditioner (if you have one) Not the best setup, but it may give you an idea on how your rx/tx would work.
unfortunately I don't have a window air conditioner anywhere in my house
 

jazzboypro

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hi, kind of new to this place.

I've been talking a lot to my parents about mounting a mag mount antenna on the roof of our house by drilling in a metal plate. meanwhile, they're skeptical about the lightning threat, but I'm more wondering about how well this would work and if it actually would be grounded?

any response helps

many thanks
At the moment i am using a cheap CB antenna with about 35 feet of cheap coax, it sits on a metal vent on the roof of my house at about 15 feet. sometime use it with a 144/440 transceiver and i can hit many repeaters that are about 30 miles away from me. i also use it with an SDS100 and an IC-R30. I do hear a lot of stuff so you might have some success with a better antenna and better coax.
 

furbox

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At the moment i am using a cheap CB antenna with about 35 feet of cheap coax, it sits on a metal vent on the roof of my house at about 15 feet. sometime use it with a 144/440 transceiver and i can hit many repeaters that are about 30 miles away from me. i also use it with an SDS100 and an IC-R30. I do hear a lot of stuff so you might have some success with a better antenna and better coax.
Really. A CB antenna for two meters and 70 cm? Be very careful or you WILL damage your radio. You NEED an antenna designed for the frequencies you are using. CB is 27 mhz while 2 meter is 145 mhz and 70 cm is 445 mhz. Just a warning. DON'T transmit if you are only using a CB antenna.
 

jazzboypro

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Really. A CB antenna for two meters and 70 cm? Be very careful or you WILL damage your radio. You NEED an antenna designed for the frequencies you are using. CB is 27 mhz while 2 meter is 145 mhz and 70 cm is 445 mhz. Just a warning. DON'T transmit if you are only using a CB antenna.
I know, i used it at low power, i should get the LMR400 this week or next week and then the proper antenna goes up. In the mean time i mostly listen.
 

KC1MZX

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ok, so at this point in the game I've got myself an antenna (diamond x-50a) but i want to use it with a portable antenna tripod, that being said I can't seem to find a tripod that would work with my antenna
 

prcguy

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For temporary base use get a PA speaker tripod, they are cheap and good for antennas. I was just using one today to test out a new antenna. Here is a good price and you can find them cheaper. Pro Audio DJ Universal Pa Speaker Adjustable Tripod Pole Mount Speaker Stand | eBay


ok, so at this point in the game I've got myself an antenna (diamond x-50a) but i want to use it with a portable antenna tripod, that being said I can't seem to find a tripod that would work with my antenna
 

K9DWB

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I've also heard of using a camera lighting tripod. I've even looked myself for something I may use in/around the apartment that's in the near future. Here's a link to the video. He mentioned 2 different plans for a better antenna for HT radios.

These sound to me to be temporary/portable. Also I'd think these are more what I call Plan D after A B and C have been eliminated for whatever reason.

Version 1 was an Amateur mobile magnetic mount and antenna and use a 13x9" cookie sheet flipped upside down. Stick the mag antenna on it and then connect the radio.

Version 2 was to use the camera lighting tripod, a trucker type mirror mount, and an appropriate antenna with cable. I myself found a tripod on B&H Photo for about $55 that's about 9.5' tall that seems interesting. A link to the tripod mentioned at B&H here. It may need some weight to stabilize.
 

GlobalNorth

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This is the reason Elmers used to exist. To help a novice operator with all kinds of questions and practical advice on what works and what doesn't.

Now, a new gal or guy has to use the internet and hope that someone will lend a hand. No offense to the OP at all, his question shows that he is trying to think his way to a solution at the lowest cost possible, based on his budget. Elmers used to be everywhere and yet, where is the ARRL and the current crop of old timers in all this? Why can't they offer a recommend to a local person eager and willing to help out? ARRL - all complaining and zero action, all the time. [Rant off]

Thank goodness the membership here is willing to offer technical advice and suggestions.

This reminds me of why I never got my ticket as a young person.
 

n5ims

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While personally I'm not a fan of them, given what you're currently using and thinking of using you should instead just get one of the Ed Fong dual band antennas (Ed's Antennas). They're J Pole antennas that are light and work rather well for a zero to minimal gain antennas. Get the ones that mount in a PVC pipe (your choice buy the pipe from him or save money and get it from Home Depot). You can strap it onto a vent pipe on your roof like is shown on his web site. Use some good 50 ohm coax (LMR 400 is good, but stiff and expensive, RG-8 is OK, but not RG-8X which is for HF work). You'll still need lightning protection but that can be done with a fairly cheap lightning arrestor (MFJ-270, LIGHTNING PROTECTOR, SO-239/SO-239, 400W PEP will work) that's attached to a ground rod and make the connection between the MFJ-270 and the ground rod as short as possible and use the largest wire that you can (solid 12 gadge minimum, 6 gadge better if it will fit your connections).

Now you should take this as the bare minimum you can do. For proper grounding and lightning protection search the forums for the many threads on this topic that show how it should be done. You can get a much better antenna, better coax, easily get a better lightning arrestor, etc. but each will increase your budget. Height is your friend for signal range, but your enemy for lightning. Your choice and good luck.
 
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