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Radio Equipment Installation Forum - Forum for discussing how to install radio communications equipment in Mobile, Base, Command Post, EOC, etc configurations.

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Old 07-07-2018, 3:25 PM
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Default Roof Mounted Mobilr Antenna

I purchased an old chiefs SUV from a fire department. When I installed my mobile in the vehicle I had a magnetic mount antenna. Well I'm am upgrading my radio and antenna. I have a one inch hole in my roof from when the fd had it. I did drop the headliner and found the old coax cable with a nmo mount its 3/4" . How did they pull that off? I want to use that existing hole. What options do I have? Thanks.
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Old 07-07-2018, 4:42 PM
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Are you sure it's a 1" hole?

If so you will have to run something like a Breedlove mount. If it's 7/8" (because occasionally upfitters fail to acquire the proper tool for the job) you can typically get it close enough to work.
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Old 07-07-2018, 4:45 PM
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You'd probably need to get creative with some sheet aluminum or stainless steel and make a big enough washer to plate to go over the hole. Seal it well, put a 3/4" hole in the center.

Or better yet, plug the 1" hole and make the correct sized hole.
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Old 07-07-2018, 5:04 PM
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I would screw a pipe flange down over the hole, add a few feet of pipe and stick a Yagi on it.
Yup.
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Old 07-07-2018, 5:04 PM
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I guess I will plug it and make a new hole. Any recommendations for an antenna for a kenwood tk-7180. The cable that is already ran is smaller than the pl-259. So it wont work with the 7180.
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Old 07-07-2018, 7:44 PM
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Yes, plug the old and start new.
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Old 07-07-2018, 7:57 PM
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Quote:
Originally Posted by oopie41091 View Post
I guess I will plug it and make a new hole. Any recommendations for an antenna for a kenwood tk-7180. The cable that is already ran is smaller than the pl-259. So it wont work with the 7180.


Probably a Mini-U, common to Motorola. Doesn’t really matter though if you are going with a new kit. Get a 1/4 VHF antenna centered to 146 MHz if you are specifically interested in 2m. You could run a 5/8 wave antenna as well but the bandwidth will be narrower.


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Old 07-07-2018, 8:52 PM
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Quote:
Originally Posted by oopie41091 View Post
I guess I will plug it and make a new hole. Any recommendations for an antenna for a kenwood tk-7180. The cable that is already ran is smaller than the pl-259. So it wont work with the 7180.
Yeah, ditto on the 1/4 wave antenna. Wide bandwidth can be handy. They are lower profile, cheaper, and if you decide you need something else later on, you are not out a bunch of money.
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Old 07-07-2018, 9:05 PM
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I am in a rural setting with high hills and low valleys all around. I need maximum range.
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Old 07-07-2018, 9:08 PM
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Also my bandwidth is 151 to 156. I don't need much more for what I need it for and all of my frequencies are narrow band.
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Old 07-07-2018, 9:18 PM
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https://www.homedepot.com/p/1-in-x-3...6832/100140896

One on the inside, one on the outside. The NMO mount will hold them in place. Seal with silicone caulk.
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Old 07-07-2018, 9:28 PM
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Quote:
Originally Posted by oopie41091 View Post
I am in a rural setting with high hills and low valleys all around. I need maximum range.


Then definitely a 1/4 wave. Gain antennas work better in flat terrain.


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Old 07-07-2018, 9:39 PM
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Roughly how long of an antenna do you suggest?
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Old 07-07-2018, 11:51 PM
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Quote:
Originally Posted by oopie41091 View Post
Roughly how long of an antenna do you suggest?
1/4 wavelength on your frequencies (151 to 156MHz) will be about 18 inches long.

You can purchase "pre-tuned" antennas that are usually right on.

https://www.theantennafarm.com/catal...n-nmoqw152-723
This antenna is 152 to 162MHz.
They are broad banded enough that they will work fine outside that range. I'm running similar antennas on my personal and work vehicles. Putting these on an antenna analyzer shows a less than 1.5:1 SWR from 144MHz to up near 174MHz.
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