How To Install Mag Mount Antenna
For years I have had great success with my trusty no-proper name mag mount 2m/440 mobile antenna. Yet, it'southward fourth dimension to consider a permanent through-hole NMO mount. NMO production information is a bit misleading then I bought several varieties to effigy out the details. I share the results below.
Despite the bad rap magnetic mountain antennas often get, they practice piece of work pretty well for VHF and upward (See previous post for details). Some spider web sites mention an issue of liability for materials not permanently secured to an auto; The proffer is magnetic antennas are not office of the vehicle unless permanently installed. If somehow your magnetic whip injures someone, auto insurance won't embrace it. I don't really know the answer to this so am asking the readers of this site to log in and comment on this point.
Then anyway, the first photo shows the roof of my Taurus in cute, scenic Fauquier County, Virginia.
Farms, countryside, cattle, horses, fifty-fifty foxes with the view spoiled by the unsightly, ugly cable coming from the magnetic mountain antenna on the auto roof top.
I never considered punching a hole in the roof of my Ford Taurus. I don't accept anything confronting this, but magazine antennas have, quite simply, ever been around to serve my mobile antenna needs. After years of weathering, it's time to consider a through pigsty mount on the quondam Ford Taurus.
CBs, K-40 and Big Momma
What, on Earth, am I talking near? I am not embarrassed to say I worked in a popular CB Shop in Fairfax, VA during the college years – 1980s. This was a superb experience. I installed CBs and Antennas in vehicles from compact cars to Firebirds to pickups to Tractor Trailers to RVs. I even designed a CB Antenna for someone'due south hot air balloon.
The easiest antenna to install was the K-40. However, another popular antenna of the day was the Antenna Specialist "Large Momma" CB aerial. This antenna was in one case found on every VA Country Police force car. The cardinal difference between the K-xl and Big Momma twist off mount was the addition of car ground connectedness whereas the K-twoscore just continued the coax heart usher. I never quite understood, and then, why a base loaded five foot whip would need a ground connexion. Fiddling did I know I saw my outset NMO mountain antenna.
New Motorola (NMO) Mounts
Back then I thought the NMO mountain was an over designed mount. Further research institute that NMO is pretty much the defacto mount used in professional person applications for antennas of all kinds. I standard threaded connexion provides for an unlimited pick of antennas that 1 can replace equally requirements change. Prissy.
NMO Through-pigsty Mountain Choices
Research on the Internet reveals quite a few selections to ponder when considering through pigsty NMO antenna mounts. Choices include:
- three/8″ or 3/4″ hole
- Open or shielded cable connection bespeak
- Name make of inexpensive knockoff
- Hole Saw or Metal Dial
3/8″ vs. iii/4″ Hole
It is quite clear the traditional installation of NMO uses a 3/4 inch hole. This is precisely what I thought I was going to practice. However, I stumbled onto one web site offering a iii/8 inch option and I had to know more.
Information technology seems the 3/viii inch choice is primarily used for mounts that must attach to very recall metallic… 1/8″ or thicker. If I tin can get abroad with a 3/8″ hole in my Taurus I was willing to try it. Allow'due south compare the advantages of each.
Advantages of iii/4″ NMO through-hole mount include:
- Mount tin be drilled and installed from the outside (Cable routing actress of course)
- Seems to exist the "way" to practise it
- 3/4 inch specialty drills available to drill hole, merely not go any deeper
Advantages of iii/8″ NMO through-hole mountain include:
- Smaller pigsty
- Potentially sturdier with smaller hole
Open or Shielded Connection Signal
While searching for NMO mounts to consider, I stumbled onto a web site showing an NMO mountain with a completely metallic enclosed connection area. This is to ensure fiddling RF energy escapes into the human occupied expanse. Evidently some countries require this. The US does not seem to take such a requirement, but I purchased one of these for review… run into below.
Proper name Brand or 'other'
One thing that became obvious after reading the forums about NMO mounts is the proposition to apply brand proper name parts from Laird, Motorola, Larson, etc. The NMO mount is standardized, but the suggestion is quality tolerances may be loose in off-make parts.
I problem I had while shopping was knowing simply what brand parts were being sold. After receipt of my examples, shown below, Laird and Antenex were the primary manufacturers. Still, only ii of the 4 vendors said so on their web site and in the sales receipts.
Pigsty Saw or Metal Punch
No one in the metal manufacture uses pigsty saws for small holes like this, however, it appears just most every installer of mobile antennas does. When installing through-pigsty CB antennas back in the day, the bossman insisted on the use of his metallic dial. It did make superb holes requiring very little de-burring.
One clear problem with punches is the demand for tool access to both sides of the metal. I tin can see where busy installers desire top only access and the pigsty saw is about the only way to go it.
Fortunately Laird and others brand a hole saw specifically for use with NMO installation. The good ones take a pilot drill bit followed by a "wood hole saw" like cylinder and, most of import, a shoulder that stops the thing from going too far into your vehicle. I did not meet such a tool for 3/8″ installation, only y'all need bottom access for this anyway, so a dial or carefully used drill may be just fine.
Pictures difficult to detect
Ane specially abrasive matter with most of the NMO Vendor spider web sites is the lack of specific pictures for the particular model yous are trying to buy. The descriptions were fine, just seeing the thing helps. So for the readers of this web site, here are some pictures of the actual items purchased.
Vendor A – Off brand NMO Mountain for 3/viii″ or 3/4″ Hole
I'm non really too hip to that aptitude metallic back support as information technology feels a bit cheap. The main barrel is for the iii/8″ pigsty, but the metal back support has as well small knockout bumps which assist middle it in a three/4″ hole.
Vendor B – Antenex (Laird) MABTO NMO Mount for 3/8″ or 3/4″ Hole
This unit has a longer barrel for thicker base-plates than the MABO (beneath). The sales receipt says precisely "Antenex iii/4″ or 3/8″ Hole NMO Antenna Thick Mount MABTO" equally did the web site when I purchased information technology. The Laird purse information technology came in says this is for a 3/8″ hole. Nonetheless, the fine print on the pocketbook describes the purpose of the white washer is a centering washer when you employ this mount in a 3/4 inch hole.
Vendor C – Laird MBO NMO Mountain for 3/iv″ Pigsty and MABO for 3/viii″ Mount
This Laird item may exist the "archetype" NMO mount. Information technology is for the traditional 3/4″ hole. The top component and backing component are actually just one piece. The backing component has a nice centering cylinder milled into it that looks like information technology volition nestle right into the hole and keep it in place. This unified unit feels and seems very solid.
This is also from Laird with the simply divergence between information technology and the MABO is the backing piece shape. This one has no 3/4 inch centering ridge milled in it.
Both the MBO and MABO Laird mounts print me.
Vendor D – Unknown Manufacturer NMO Mountain for 3/4″ Hole with FME Connector
This product contains a 90 degree coaxial connector. The RF energy is plain well independent. There are only 2 pieces and the bottom portion is ane solid cake of metal. I don't know a lot about the FME connector.
Conclusions
Laird (Antenex) easily won my admiration for quality and part. Vendor mis-data and lack of production specifics forces the buyer to do their own inquiry into product option. I hope the pictures of bodily products above assistance yous select the best NMO through-hole for your application.
My final choice is likely between the MBO and MABO. Upon shut examination the only real difference betwixt the two is the milled 3/4″ circular "shelf" on the MBO inner human foot and the size of the threaded connexion between the tiptop and bottom pieces. Many reports from the field suggest the 3/4″ MBO way is "much stronger" than the 3/8″ MABO way, but the folks never seem to accept any inkling every bit to why. The outer dimensions of the inside foot for each are identical and, thus, transfer stresses to the metal identically. The cylinder of metal between the ii is the same bore. It's plainly obvious the 3/8″ unit transfers mechanical stress over a larger surface expanse of vehicle metal with the smaller pigsty. I will paradigm both onto a fleck piece of metal, show information technology to some machinists and MEs to go their take on this.
Several friends note the 3/4 mount offers the benefit of installation entirely from the outside of the vehicle adding… "The unabridged cable harness with NMO mountain can be removed equally one slice and reinstalled in another vehicle if you utilise the iii/4 inch version." This is a serious reward and seems to be the practical reason the iii/4 inch version is so popular.
More than details to come.
73
John, kx4o
Source: https://www.hamradio.me/antennas/nmo-mobile-antenna-mount-options.html
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