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Author Topic: Where to find GENUINE Motorola NMO mounts or EXACT versions from others?  (Read 4860 times)
KC0LPV
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« on: June 26, 2011, 12:06:18 AM »

I called an amateur shop last fall and ordered an NMO mount.  I didn't get around to doing the install until this weekend (busy year) and this mount is odd.  It is marked "Laird Technology" on the coax and bag, and turns out to be a 3/8" mount with a spacer for a 3/4" hole.

I suppose I can use this, but I thought it was the same high-quality mount I bought there before.  Apparently they changed suppliers.

I have been googling and checking catalogs left and right, and I can not find ANYONE who sells actual, genuine, made-by-Motorola "Motorola NMO" mounts.  There's plenty of places that sell "Motorola NMO" mounts that turn out to be made by any of a dozen different companies that aren't Motorola.

Since I don't know what companies have fully-licensed, exact duplicates of the Motorola mount, I am stuck with the one I have until I can either find out (help?) what manufacturers make those exact duplicates, or I can find a supplier that actually sells Motorola NMO mounts.

If you know answers to either need...I'd appreciate it.  K0BG, you out there?
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K0BG
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« Reply #1 on: June 26, 2011, 11:50:57 AM »

Buy a Larsen.

The Laird will work, but it is a little more difficult to use in a 3.4 inch hole.

Incidentally, Larsen makes a convertible NMO with a changeable center pin. I read someplace that the mount would be come standard, so make sure the center pin (flat surfaced one) is present.
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KC0LPV
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« Reply #2 on: June 26, 2011, 07:51:03 PM »

Thanks, K0BG.  One more question.  I've been looking for a specification for how high the center pin is supposed to be from the flat surface of the mount.  This seems like it would vary depending on the sheet metal it was attached through, right? 

I have a generic mag-mount NMO where the pin measures 2.0 mm proud of the flat surface.  On the Laird I just assembled, I may have tightened it a bit much...it seems to be about 2.8mm proud.  I have been looking through the google results for "NMO mount specifications" and "NMO mount center pin height" with exactly zero luck.  Do you know a spec and tolerance?
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K0BG
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« Reply #3 on: June 27, 2011, 06:13:49 AM »

Just from looking, I'd say the center sticks up about 1/16 inch. It is fixed regardless of the thickness of the sheet metal.

This is as close as you're going to get. Note further down the page, the convertible mount I mentioned before.

http://www.larsen-antennas.com/docfiles/ASB10/Mounts.pdf
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KC0LPV
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« Reply #4 on: June 27, 2011, 10:11:45 AM »

The one I have looks most like the one on the bottom of p. 166 in the pdf you linked.  The further down the brass collar is screwed, the higher the center conductor is in relation to the brass collar's flat surface.

Mine is a Laird MAB8PS.  I'm looking for the Larsen or Motorola branded NMO mount at my closest amateur shop...until then it would be nice to get on the air with this mount.  I'll go look for a brass or bronze fender washer to use as a spacer.
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VA3WXM
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« Reply #5 on: June 27, 2011, 11:15:15 AM »

I've only used Larsen's 3/4" NMO mounts and have had no issues.

The height of the centre pin will vary relative to the threaded collar and that's a function of the thickness of the metal surface you're mounting it on.  Larsen NMO antenna coils all have silver plated tabs for the centre conductor that will conform to the height of the centre pin of the mount.
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KC0LPV
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« Reply #6 on: June 27, 2011, 12:12:21 PM »

Is the Larsen antenna base design (like you mention, VA3WXM) the "standard" Motorola design?
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K0BG
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« Reply #7 on: June 27, 2011, 01:38:37 PM »

Automotive sheet metal is seldom heavier than 10 Ga, especially nowadays. You can buy NMO mounts made for thicker material, but when body mounted, you shouldn't need them.
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KC0LPV
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« Reply #8 on: June 27, 2011, 03:53:05 PM »

Okay, adding a single 3/8" x 1.5" x 1.2mm stainless steel fender washer results in a center contact 1.2mm proud of the flat surface of the mount, and (using a dry-erase marker to mark the mount surface to test) good contact between the antenna's internal neoprene ring seal and the mount when fully tightened.  (This is my old Comet SBB5-NMO.)

My fender mount is 2mm thick stainless steel, and the washer adds another 1.2mm, for a total "sheet metal" thickness of 3.2mm, or about 0.126".  Looks like that's between 10 and 11 gauge sheet steel thickness.

This should work until I can afford to upgrade antennas and mount.
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KC0LPV
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« Reply #9 on: June 28, 2011, 10:00:41 AM »

By the way, the serrated-edged ears on the back of the mount were bent enough to tell with a straightedge, so I probably bent them when tightening it down the first time.  This mount might have been fine in the first place if I hadn't tightened it as much as I did.
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VA3WXM
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« Reply #10 on: June 28, 2011, 10:07:05 AM »

Is the Larsen antenna base design (like you mention, VA3WXM) the "standard" Motorola design?

I honestly couldn't tell you.  I've only ever used Larsen antennas with the mounts.  I tried some Comet "NMO" antennas and they wouldn't screw down properly, apparently because the thread pitch is slightly different (according to what Alan K0BG has said in the past).
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KC0LPV
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« Reply #11 on: June 28, 2011, 12:47:19 PM »

My SBB5-NMO screws down without any binding or other problems, so if the thread pitch is a problem then I sure can't feel it.  The Comet does have a spring loaded button rather than the little silver tab, and that was what was causing my antenna to not seat when I had almost a 3mm high center contact.  The spring loaded button was being pushed all the way in, and the antenna 'bottomed out' against the contact base.

Now, with only about a 1mm high center contact, it works perfectly.
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K5LXP
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« Reply #12 on: June 30, 2011, 06:54:17 AM »

I have been googling and checking catalogs left and right, and I can not find ANYONE who sells actual, genuine, made-by-Motorola "Motorola NMO" mounts.  There's plenty of places that sell "Motorola NMO" mounts that turn out to be made by any of a dozen different companies that aren't Motorola.

Have you tried the phone book?  I buy my real-live, genuine Motorola replacement parts from the local 2-way shop here that both stocks or can order Motorola factory parts.

I don't think you can go wrong with the Larsens but if it's genuine circle-M you want, you can certainly get it.

FWIW, I'd be surprised if Motorola made the mounts, they're likely outsourced by one or more vendors.  Larsen possibly one of them.


Mark K5LXP
Albuquerque, NM
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KC0LPV
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« Reply #13 on: June 30, 2011, 07:35:44 PM »

Yep, no 2-way shops anywhere around here.  Closest one is over two hours away in another state.
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K1CJS
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« Reply #14 on: July 01, 2011, 04:36:57 AM »

Find out who does the two way installs for your police/fire department, and go to them.  You can probably get a Motorola NMO mount there--just be prepared to spend more than you would at a ham shop.
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