Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Diamond antenna into Maxrad NMO base OK ?  (Read 472 times)
KC2MPG
Member

Posts: 65




Ignore
« 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?
Logged
K1CJS
Member

Posts: 6055




Ignore
« 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.
Logged
K0BG
Member

Posts: 9883


WWW

Ignore
« 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
www.k0bg.com
Logged

Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!