HELP! Damaged NMO hole mount

Jay G. · Post by **Jay G.** » Sun Jan 12, 2003 10:12 am

HELP! I have a 1999 Tahoe Chiefs vehicle with 3 roof antennas. One of the holes is damaged and wont accept a standard NMO mount. Is there anything I can do without drilling a new hole?? Is there some type of mount that I can use?? HELP!!!!

Please email me directly - [email protected]

Thanks!

Post by **wavetar** » Sun Jan 12, 2003 11:10 am

There are kits available for "thick roof" mount vehicles, such as armoured trucks, certain fire trucks & ambulances, etc. They are essentially a threaded center, about 3/8" around, and about 1+1/4" long. It pokes up from the bottom of the roof. A modified type of brass ring threads down over it from the top, giving you your NMO type mount. You could use one of these kits along with a small square of 1/8" thick sheet metal on both sides of the hole to mount the antenna. I don't know the part number off hand. Make the top, outside square (or circle, if you have the means) just slightly larger than the hole, maybe 1" across, then use a good dose of silicone to seal it all up.

Todd

Post by **HumHead** » Sun Jan 12, 2003 11:34 am

Maxrad makes an XNGP flange mount, originally designed for fiberglass bodies, that you could probably make work.

Here's a link to the Tessco site (Tessco SKU # 38893)

http://www.tessco.com/products/inv_disp ... lsku=38893

perthcom · Post by **perthcom** » Sun Jan 12, 2003 11:35 am

Hi..
Guess it depends on how big the hole is now.

I had a cabby in last week who had tried to install his own antenna, complaining about poor range. He had drilled a 1" hole so his antenna was loose. I used a "U" shaped retainer from a Motorola handset cup to bridge the fingers on the underside of the NMO mount... the brass nut was just big enough to not fall though the hole. Then I added a bit of silicon on the antenna nut seal for good luck.

Another solution (you didn't say what band or gain the antenna was)... Larsen has a line of antennas called "OM" mounts. They are a flange mount antenna and should cover the damaged hole. Since they are designed as 1/2 wave antennas, they provide some gain on a metal room.

ASTROMODAT · Post by **ASTROMODAT** » Sun Jan 12, 2003 12:52 pm

Hope you don't mind rain inside of your headliner and low trade in value is O.K. for your needs...

2wayguy · Post by **2wayguy** » Sun Jan 12, 2003 2:00 pm

Todd had the best idea. I have a competitor close to me that drills the next size up hole from 3/4" so he can poke the NMO up from the bottom. After a year or so the hole rusts and the NMO falls off. I have found that after cleaning the hole up, I use the thick mount that Todd describes with big stainless washers. Works well, Antennas tune fine and there are no leaks.

Haydn

n5tbu · Post by **n5tbu** » Sun Jan 12, 2003 3:55 pm

Antenna specialists used to make a repair kit for that problem.It consisted of 2 very thin stainless washers with a 3/4 hole and the washer was about 1.5 inches in diameter.Sorry I don't remember the part number.

Jim202 · Post by **Jim202** » Sun Jan 12, 2003 5:46 pm

I guess part of the answer is how bad the hole was damaged. There are a number of good sugestions already given. If the roof is just bent up some, you may be able to beat it back into a resemblence of being flat. A socket wrench on top and a block of wood underneath can do wonders. Just some tender loving care from a hammer thrown in. May take 2 people to properly do.

Many years ago I took over a very large cement company operation. The old radio shop had been using the 3/8 inch mounts and the old standby 3/4 ASP stand up to anything mount. Only problem all the tree limbs they were hitting was causing them to pay a fortune to the body shop to repair all the cement mixer roofs.

Asked them if they would rather put a new coil and whip on the roof or pay the body shop. (drivers never picked up the damaged antenna) The company answer was it was far cheaper to keep replacing the Larson coils and whips than take the truck out of service for a couple of days and pay the body shop.

Before everyone on here goes and yells about the quality of the Larson antenna coils, they did the job. I never said they take a beating. What I said was they cost less than the body shop.

The plastic in the Larson coils are soft enough that the car or truck generally will not have any sheet metal damage. Just the coil cracks and falls off. Always kept a stock of spare coils and replacement whips in the van.

Jim

ASTROMODAT · Post by **ASTROMODAT** » Sun Jan 12, 2003 5:54 pm

Re-use the antenna and replace the car. Problem solved.

Al · Post by Al » Sun Jan 12, 2003 10:39 pm

One option you may have that I've noticed hasn't been mentioned: Depending on how badly the original 3/4" hole is damaged, use a 3/4" or 7/8" rubber hole plug that Mot sells with a little silicone sealer under the outside lip(quite wide), then remount the antenna adjacent to the damaged area. Remounting will assure you of a good low impedance ground. No wet headliner!

ASTROMODAT · Post by **ASTROMODAT** » Sun Jan 12, 2003 10:50 pm

Better yet, cut the top of the car off and turn it into a permanent convertable. Then, sell it to someone in So Cal, and tell 'em to use a fendor mount Larsen setup, if they need a 2-Way radio. You can use the old car roof for a ground plane for a base station antenna with the old NMO. Simple.