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Author Topic: Diamond antenna into Maxrad NMO base OK ?  (Read 671 times)

Posts: 65

« on: April 15, 2005, 07:22:33 AM »

I have a Diamond antennz on my car and am using an old Maxrad nmo mag mount base. I had the base from my old GMRS days. The diamond screws into it ok, but for some reason does not look like a "perfect" match. The tiny metal tab on the antenna already broke off one and I had to buy a new antenna. So my question is, are all NMO mag mount bases universal?

Posts: 6231

« Reply #1 on: April 15, 2005, 08:26:25 AM »

NMO antenna mounting bases are all supposed to be the same, but there are differences between manufacturers.  I think Motorola was the originator of the NMO type mount.  Many manufacturers have made copies of it, some thicker than the original as measured from mounting location to top of mount, some have different measurements of the hole drilled into the place where it is mounted. (Motorola starting by using the original 3/4" hole measurement and some others manufacturers designs need only a 5/16" hole now.)

If the antenna doesn't look right on the mount in your case it is because of the two different manufacturers making the antenna and the mount as you pointed out.

If the antenna is a short one and doesn't weigh too much, I wouldn't worry about it even if there's a space between the antenna base and the mount base, unless the antenna won't thread onto the mount properly.  But if the antenna has any amount of height or a heavier loading coil on it, it would be wise to get the Diamond mount so the antenna itself is properly supported and won't break off at the collar at the very base.  

Other than that, the two mounts, both being NMO style are pritty much identical as far as impedance goes.

Posts: 10211


« Reply #2 on: April 15, 2005, 09:19:29 AM »

Chris was correct in that Motorola was the originator; NMO as in New Motorola. Unfortunately, they are not all the same. One of the best attributes of the original 3/4" NMO is that it is waterproof even when the antenna is removed. The smaller 3/8" and 5/8" ones are not.

You might think this wouldn't be a worry with a mag mount, but it is. Rain water mixed with dirt and road grime will corrode the contacts with obvious results. This occurs when there is a mismatch between manufacturers.

Lastly, I don't like mag mounts for safety reasons. In the event of a crash, they come off and become flying missiles which can maim and kill. Don't laugh as there has already been one reported death caused by one. By the way, most insurance companies will not insure any device not permanently mounted to a vehicle. Caveat Emptor.

Alan, KØBG

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