Selecting an NMO mount (variations to choose from)

[VA3WEX]

Planning the installation of a drilled NMO mount in the centre of the roof of my 2019 RAV4 for a CB antenna.

Have a few questions with respect to NMO mounts, as there seems to be quite a bit of variation in them and I don't know the technical differences implied by the geometric differences.

Some NMO mounts are tiny, almost "stethoscope size", like the Larsen NMOHF and its variations: https://static.dxengineering.com/global/images/technicalarticles/lsn-nmokhfcxpl_lw.pdf

Motorola mounts are also very small:

Motorola 3080384M48 Antenna Roof Mount - Radioparts

<p>The Motorola 3080384M48 is a ¾ roof antenna mount with 17 ft. of RG58A/U cable, mini-UHF crimp.</p>

www.radioparts.com

Breedlove, on the other hand, has three models of NMO mounts, all with large, thick, discs:

• #503 needing 5/8" hole, has 2" disc 3/8" thick. NMO Roof Mount # 503
• #504 needing 5/8" hole, has 3" dia. disc 3/8" thick. NMO Roof Mount #504
• #505 hole dia. not given, has 4-1/2" disc but thickness not given. NMO 4 1/2 in. Puck w/ Ring Terminal # 505

So--what are those discs for?

What would make me want to choose between the two extremes of no disc at all vs. 4-1/2" disc?

 

[mmckenna]

The Breedlove mounts are designed to spread the force of a really large antenna over a wide area. I'm sure there's good reasons to need something like that, maybe if you were going to run an NMO - 3/8x24 type adapter. I ~think~ you need access to both sides of the roof, which can be a real PITA, where the standard NMO mounts do not require that.

If you are going to run one of the common NMO mount CB antennas from Larsen, Laird, etc. you don't need those. The standard NMO mounts from Larsen are plenty. I've run NMO mounts for 30 years and I have Larsen NMO-27 antennas that are that old. Never once did I have an issue with the standard NMO mounts, even hitting tree branches, low parking garages, etc.

The nice thing about the regular style NMO mounts is that they are very easy to install once you drill the hole. No access to the underside needed. Also looks a lot better if you go to sell the vehicle and just put an NMO rain cap on top.

And while the NMOHF style mounts are nice, the older style NMO mounts are just fine for what you are doing. The HF mounts are designed for use up to 6GHz. The price difference is usually minor, so which ever one you choose will be fine.

 

[VA3WEX]

If you are going to run one of the common NMO mount CB antennas from Larsen, Laird, etc. you don't need those. The standard NMO mounts from Larsen are plenty.

That is indeed my plan.

Thanks, that was helpful!

 

[slowmover]

Planning the installation of a drilled NMO mount in the centre of the roof of my 2019 RAV4 for a CB antenna.

Have a few questions with respect to NMO mounts, as there seems to be quite a bit of variation in them and I don't know the technical differences implied by the geometric differences.

Some NMO mounts are tiny, almost "stethoscope size", like the Larsen NMOHF and its variations: https://static.dxengineering.com/global/images/technicalarticles/lsn-nmokhfcxpl_lw.pdf

Motorola mounts are also very small:

Motorola 3080384M48 Antenna Roof Mount - Radioparts

<p>The Motorola 3080384M48 is a ¾ roof antenna mount with 17 ft. of RG58A/U cable, mini-UHF crimp.</p>

www.radioparts.com

Breedlove, on the other hand, has three models of NMO mounts, all with large, thick, discs:

• #503 needing 5/8" hole, has 2" disc 3/8" thick. NMO Roof Mount # 503
• #504 needing 5/8" hole, has 3" dia. disc 3/8" thick. NMO Roof Mount #504
• #505 hole dia. not given, has 4-1/2" disc but thickness not given. NMO 4 1/2 in. Puck w/ Ring Terminal # 505

So--what are those discs for?

What would make me want to choose between the two extremes of no disc at all vs. 4-1/2" disc?

Antenna choice. An NMO34b + WD640 whip is as large antenna that type foreseen.

Someone wants to run something taller or with a mid-coil exerts a far greater wind load.



Versus



Non-NMO mount (adapter onboard), but truly high load antennas also aboard. This 7’ is one of the little ones (in load).

.