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New Generation NMO Mount needed

This forum is dedicated to helping people with questions about installing radio equipment in vehicles. This can include antenna installs, electrical wiring questions/problems, and mounting systems. Pictures of installs are welcome.

Note: Discussions regarding lighting, sirens, and other equipment now has its own forum in the 'off-topic' section below.

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fineshot1
Posts: 910
Joined: Wed Oct 12, 2005 5:13 am

New Generation NMO Mount needed

Postby fineshot1 » Thu Jul 14, 2016 7:31 am

This is just a wish we had kind of thing.

The most common problem i have when installing NMO mount
assemblies is the collar with the o ring. The o ring most of the
time does not stay put in the collar and i hate that silicone crap
as it gets my fingers all slimey and messy.

It seems to me the manufactures could make a collar that has the
o ring impregnated into it that does no pop out. This new collar
is long overdue as far as i am concerned.
fineshot1
NJ USA

User avatar
Bill_G
Posts: 3055
Joined: Thu Sep 17, 2009 5:00 am

Re: New Generation NMO Mount needed

Postby Bill_G » Thu Jul 14, 2016 3:36 pm

Never had a problem except when I *don't* grease the o-ring. It just takes a tiny bead. Seat it by hand first, and then tighten it up. The thinner sheet metal in new vehicles is making it difficult to get a good tight fit without deforming the roof.

Jim202
Posts: 3485
Joined: Sun Sep 09, 2001 4:00 pm

Re: New Generation NMO Mount needed

Postby Jim202 » Thu Jul 14, 2016 3:45 pm

fineshot1 wrote:This is just a wish we had kind of thing.

The most common problem i have when installing NMO mount
assemblies is the collar with the o ring. The o ring most of the
time does not stay put in the collar and i hate that silicone crap
as it gets my fingers all slimey and messy.

It seems to me the manufactures could make a collar that has the
o ring impregnated into it that does no pop out. This new collar
is long overdue as far as i am concerned.


Obviously your not in the two way business. A rag and a little solvent resolves your slimy problem as you call it. What I don't like is the trash silicon grease they supply. When it gets hot, it tends to liquefy and start to flow all over the place. I solved that messy problem by switching to using 3 M High vacuum grease. It is silicon based, but a different chemical mix. it doesn't flow when hot and sticks good. Found it is really good for holdong those pesky O rings in place while you try to install the brass nut to secure the NMO mount in place.

Jim

fineshot1
Posts: 910
Joined: Wed Oct 12, 2005 5:13 am

Re: New Generation NMO Mount needed

Postby fineshot1 » Thu Jul 14, 2016 5:54 pm

Jim202 wrote:Obviously your not in the two way business. Jim


Jim As usual you are 180 degrees out of phase with the truth.

I also hate the cable zig zag bundle in the plastic bags. After
you get bags of NMO assemblies they have already been in these
bags for many months. The cables are difficult to smooth out
after being bundled in this zig zag configuration. They should be
coiled instead of the zig zag bundle. This would be better for the
cables and would ease installation instead of having to smooth out
the cable bumps formed by the zig zag bundling. When you work alone
with no one else working with you to guide the cables through the 3/4"
hole this is a must.

Face it guys - this present nmo configuration is long in the tooth
and certainly can be improved with my new collar suggestion but
with the old man attitude nothing ever changes. I got this idea from
looking at collars used in the plumbing industry - these collars have
o rings imbedded in the brass collars.
fineshot1
NJ USA

User avatar
kb4mdz
Posts: 269
Joined: Tue Oct 02, 2001 4:00 pm
What radios do you own?: Too many for the time I have.

Re: New Generation NMO Mount needed

Postby kb4mdz » Thu Jul 14, 2016 6:33 pm

Ahh, the tyranny of a large installed base of less-than-optimal technology. Kinda like the QWERTY typewriter layout.

I gotta admit, he's got a point about the bundle that is currently used; putting 'curves' into the coax. My solution for fineshot1 would be to open the package of cable as one of the first tasks of an install, and straighten it out by hand, possibly even stretch it out on the floor to relax for a while before you have to route it in the vehicle. Maybe even run it around a 3 or 4 inch diameter pipe, lightly, to pull out some of those bumps.

I've recently taken to doing this to Moto power cables, like around the leg of the workbench, just to relax the wire & make it easier to deal with than the constant curl from being wound in a circle.

And look at what 3/4" mounts you're using - some brands, the hole is big enough to put the brass body up thru from the bottom, and some aren't.

just my $0.02.

User avatar
Bill_G
Posts: 3055
Joined: Thu Sep 17, 2009 5:00 am

Re: New Generation NMO Mount needed

Postby Bill_G » Fri Jul 15, 2016 4:43 am

The cable bundle never caused me any problems either. I hold on to the NMO end, and toss the bundle - it uncoils almost perfectly almost every time. Sometimes I make a mess, but, you know. I drape it over a mirror or something, and let it relax.

fineshot1
Posts: 910
Joined: Wed Oct 12, 2005 5:13 am

Re: New Generation NMO Mount needed

Postby fineshot1 » Fri Jul 15, 2016 5:59 am

Bill_G wrote:The cable bundle never caused me any problems either. I hold on to the NMO end, and toss the bundle - it uncoils almost perfectly almost every time. Sometimes I make a mess, but, you know. I drape it over a mirror or something, and let it relax.


I NEVER got any that were coiled - all were and have been zig zag bundled. All from PCTel/Maxrad viaTessco and
as i work for local gov i have no say as to to whom we buy from
fineshot1
NJ USA

User avatar
Bill_G
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Joined: Thu Sep 17, 2009 5:00 am

Re: New Generation NMO Mount needed

Postby Bill_G » Fri Jul 15, 2016 7:14 am

We've been using those lately too because the bottom is sealed - perfect for TMB mounts to prevent water damage to the exposed underside of the mount. On a school bus Trbo upgrade campaign, where we press almost everyone into installs to knock out +30 in a day, I don't recall having a problem giving those a toss to uncoil either. Give it a try next time. Hold the mount with two fingers while keeping the bundle held with your thumb and other two fingers. Snap toss the bundle overhand, almost like cracking a whip. It should accordion out. It takes practice.

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giguchan
1 Warning for RSS/CPS Wanted/For Sale/Links
Posts: 496
Joined: Fri Mar 14, 2003 10:36 pm
What radios do you own?: CDM 1550's UHF/VHF HT1550'S

Re: New Generation NMO Mount needed

Postby giguchan » Sat Jul 16, 2016 2:35 pm

30 installs a day?
Radios by Fisher-Price? Never!!!
I use /\/\otorola!!
Cheers
73, de'N2GIG

Birken Vogt
Posts: 259
Joined: Thu Nov 10, 2005 7:53 pm

Re: New Generation NMO Mount needed

Postby Birken Vogt » Thu Aug 04, 2016 3:06 pm

First off I rarely use Maxrad mounts. Always NMOKxxx variations for a number of very specific reasons.

That being said I cannot remember having greased the oring at any time. It seems that if I pull up on the ring/nut while screwing down, it centers the toggle in the 3/4" bore and then the oring is only in contact during the last 2 turns or so. If it wants to fall out then I just let it lay there and locate it carefully and screw the nut down onto it instead.

However, I don't like the Maxrad style coil base either. If I do use one I put a flat washer down like the QW152 uses. That way if the oring in the nut is damaged or missing we are not relying on that plus the upper flat ring around the center pin to seal water.

I much prefer the Pulse/Larsen NMOKUD or NMOKHFUD mounts. NMOKUD was the old standard and has a solid center conductor which terminates much better and is good for a higher frequency. NMOKHFUD has a better type of RF connection in the base but the cast aluminum toggle does not bite the underside of the car roof nearly as well, but it works better for keeping radiation out of the cab for cell boosters and the like, plus I like it on general principles.

I also like the B series antennas from Laird. They have the same oring problem as above but the same solution as I typed, plus it does not seem so severe when dealing with the antenna itself as with the lock nut. Plus the center conductor pin is better.

All this stuff you can get from Tessco as well so give it a try if you are allowed.

jhooten
Posts: 290
Joined: Sat Mar 06, 2004 12:58 pm

Re: New Generation NMO Mount needed

Postby jhooten » Thu Aug 04, 2016 3:22 pm

Throw the o-ring away and fill the grove with RTV.

User avatar
Bill_G
Posts: 3055
Joined: Thu Sep 17, 2009 5:00 am

Re: New Generation NMO Mount needed

Postby Bill_G » Thu Aug 04, 2016 5:11 pm

giguchan wrote:30 installs a day?


Yeah. We can knock them out as a crew. Five guys. Everyone gets a task and they do that on every vehicle. The simple tasks like take out the old bracket and put in the new one takes one guy. Power cables takes two guys because it goes slower. I usually do the antennas. And one guy has to keep track of the paperwork - serial numbers to vehicle numbers especially on Trbo systems where unit id becomes crucial information. That guy also bats clean up - follows into every vehicle to finish anything forgotten. That job usually goes to the guy holding the account. We're there to support him, and he has to fix anything down the road. So, he sets the criteria.

User avatar
Bill_G
Posts: 3055
Joined: Thu Sep 17, 2009 5:00 am

Re: New Generation NMO Mount needed

Postby Bill_G » Thu Aug 04, 2016 5:13 pm

jhooten wrote:Throw the o-ring away and fill the grove with RTV.


I keep the O-ring, but a dab of RTV helps lube the rubber as I'm tightening down so it doesn't fold, and it helps seal microgaps in the surface.

User avatar
Bill_G
Posts: 3055
Joined: Thu Sep 17, 2009 5:00 am

Re: New Generation NMO Mount needed

Postby Bill_G » Thu Aug 04, 2016 5:15 pm

Birken Vogt wrote:First off I rarely use Maxrad mounts. Always NMOKxxx variations for a number of very specific reasons.

That being said I cannot remember having greased the oring at any time. It seems that if I pull up on the ring/nut while screwing down, it centers the toggle in the 3/4" bore and then the oring is only in contact during the last 2 turns or so. If it wants to fall out then I just let it lay there and locate it carefully and screw the nut down onto it instead.

However, I don't like the Maxrad style coil base either. If I do use one I put a flat washer down like the QW152 uses. That way if the oring in the nut is damaged or missing we are not relying on that plus the upper flat ring around the center pin to seal water.

I much prefer the Pulse/Larsen NMOKUD or NMOKHFUD mounts. NMOKUD was the old standard and has a solid center conductor which terminates much better and is good for a higher frequency. NMOKHFUD has a better type of RF connection in the base but the cast aluminum toggle does not bite the underside of the car roof nearly as well, but it works better for keeping radiation out of the cab for cell boosters and the like, plus I like it on general principles.

I also like the B series antennas from Laird. They have the same oring problem as above but the same solution as I typed, plus it does not seem so severe when dealing with the antenna itself as with the lock nut. Plus the center conductor pin is better.

All this stuff you can get from Tessco as well so give it a try if you are allowed.


Dabbing the grease on the o-ring first, and then inserting it into the brass ring helps retain it as you tighten down. They don't walk out.

Jim202
Posts: 3485
Joined: Sun Sep 09, 2001 4:00 pm

Re: New Generation NMO Mount needed

Postby Jim202 » Thu Aug 04, 2016 8:07 pm

I tend to use some high vacuum grease by 3 M. It doesn't flow with the heat from the sun and make a mess on the vehicle roof over time. It stays in place.

The other reasons for using the grease is that 1. it holds the O ring inside the bottom of the brass lock down nut. Then it also helps weather seal the antenna mount to the roof. Another place I put the grease on is the threads of the brass lock down nut. This way if you ever have to remove the mount after several years, it comes off easier. There is no corrosion on the threads. It even helps you tighten down the brass nut. Just be careful you don't over tighten it with the grease on the threads. it will turn much easier with the grease applied.

If your antenna has a metal threaded bottom, then by all means, put some of the grease on the antenna mount itself. Again I suggest the use of the 3 M high vacuum grease so it doesn't migrate off the threads an make a mess on the roof like the silicon grease supplied with most antennas.

But as with all suggestions to those that have done it their way for years, they probably won't listen to new suggestions.

Jim


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