What antenna type is this?

[Dusbark]

Hello folks, I'm new to CB radios, so I apologize for my naivety, but I have an older ram that has this mount located on the roof. I've found that a 3/4 nmo cap fits it, but the nmo adapter that I inherited gets hung up on the center pin. I've found a pl-239 connector inside the truck that appears to run up to the roof, as well as another connector that is basically a smaller version of the pl-239. I'm wondering what type of antenna I need to go on this mount, as I'd like to use it, as well as which connector it might go to, if you have any idea, please let me know. Thanks.

 

[jwt873]

Looks like an old Larsen LM mount..

 

[nd5y]

Looks like an old Larsen LM mount..

That's not an LM mount. This is an LM mount -> PulseLarsen Antennas | LMB

 

[kf8yk]

Not a LM mount, the center post would be thicker & threaded.

Looks like the old Antenna Specialists high frequency mount used on their early cellular/SMR antennas. I suspect that the mounting hole is only 3/8", you could replace it with a mount like this one without having to enlarge the hole:

https://www.theantennafarm.com/catalog/mobile-antenna-mounts-264/permanent-hole-mounts-266/3-8-nmo-hole-mounts-1291/

 

[kf8yk]

I've found a pl-239 connector inside the truck that appears to run up to the roof, as well as another connector that is basically a smaller version of the pl-239.

The 'smaller version PL259' is probably a mini-UHF, a very common connector for early mobile car phones & SMR radios.

 

[mmckenna]

That's definitely not an LM mount.

Disassemble it and see what size the hole is underneath. I agree, probably 3/8", but make sure.

Replace the whole thing with a NEW NMO mount, either 3/8" mounting hole or 3/4".

 

[prcguy]

This is what I think it is also. I have a couple of old A/S mounts I can dig up and post a pic if needed.

Not a LM mount, the center post would be thicker & threaded.

Looks like the old Antenna Specialists high frequency mount used on their early cellular/SMR antennas. I suspect that the mounting hole is only 3/8", you could replace it with a mount like this one without having to enlarge the hole:

https://www.theantennafarm.com/catalog/mobile-antenna-mounts-264/permanent-hole-mounts-266/3-8-nmo-hole-mounts-1291/

 

[kf8yk]

After a little searching I'll have to change my guess to a 3/4" hole.

It's an Antenna Specialists (now PCTEL) K166 mount. Here's the datasheets & installation instructions: Specialty Mounts for Mobile Antennas - PCTEL

mmckenna's advice still stands, remove it & replace with a proper NMO mount.

 

[Dusbark]

Alright, thanks for the replies. Before I go tearing apart the old trim on the truck to remove and replace it, what's the problem with the k166 mount? I'm only looking to do nearby truck-to-truck comms, so I'm not too worried about range. Also, I see those antennas have a bunch of different mHz ratings, what's the difference for those? Thanks fellas.

 

[kf8yk]

The K166 mount is unique to A/S and only a limited number of A/S branded antennas will fit, none of them are suitable for CB.

The NMO mount is the de facto industry standard. With the NMO you'll have the widest choice of CB antennas to pick from.

 

[TedTobias]

Definitely so 70s!

 

[cmdrwill]

IF you really want to be a cheep skate, file down the center pin and make sure it IS flat. Should be 1/8 to 3/16 above the mount.

And you DID check the mount and cable for continuity and no shorts?

 

[Dusbark]

The K166 mount is unique to A/S and only a limited number of A/S branded antennas will fit, none of them are suitable for CB.

The NMO mount is the de facto industry standard. With the NMO you'll have the widest choice of CB antennas to pick from.

Alright, sounds good. That kinda sucks, I was hoping to use it, since it doesnt leak at all. I haven't got into the cable, as most of it is under brittle trim, and headliner. So with that, what is a decent nmo antenna?

 

[Dusbark]

IF you really want to be a cheep skate, file down the center pin and make sure it IS flat. Should be 1/8 to 3/16 above the mount.

Have you done this with success? I might humor myself and try it before I go pulling the headliner and all that

 

[mmckenna]

Alright, sounds good. That kinda sucks, I was hoping to use it, since it doesnt leak at all. I haven't got into the cable, as most of it is under brittle trim, and headliner. So with that, what is a decent nmo antenna?

If you are carful, you can remove the mount from the outside of the truck. There will probably be a bit of slack in the original coaxial cable.
Carefully cut the coaxial cable where it enters the old mount.
Attach the new coaxial cable to the end of that -very-securely-
Now —carefully— start pulling gently on the radio end of the old coaxial cable.

If you are lucky, you can pull the new coax cable in that way.

A properly installed NMO mount will not leak. I've been installing them for 30 years and never had one leak.

A really good NMO CB antenna is the Larsen NMO-27. I have one of those that is about 30 years old and still works like new. It's hit a lot of tree branches and low parking garage on the top of a full size truck and has never let me down.

If you want to do this right, don't cheap out on components. There are low cost ham/hobby grade antennas and mounts out there on the market. Yeah, they'll work, but for a few bucks more you can get the higher quality professional grade stuff. Stick with Larsen, Laird, Antenex, Comtelco.

 

[Dusbark]

If you are carful, you can remove the mount from the outside of the truck. There will probably be a bit of slack in the original coaxial cable.
Carefully cut the coaxial cable where it enters the old mount.
Attach the new coaxial cable to the end of that -very-securely-
Now —carefully— start pulling gently on the radio end of the old coaxial cable.

If you are lucky, you can pull the new coax cable in that way.

A properly installed NMO mount will not leak. I've been installing them for 30 years and never had one leak.

A really good NMO CB antenna is the Larsen NMO-27. I have one of those that is about 30 years old and still works like new. It's hit a lot of tree branches and low parking garage on the top of a full size truck and has never let me down.

If you want to do this right, don't cheap out on components. There are low cost ham/hobby grade antennas and mounts out there on the market. Yeah, they'll work, but for a few bucks more you can get the higher quality professional grade stuff. Stick with Larsen, Laird, Antenex, Comtelco.

How do I go about removing it from the outside? Could I stick a pair of needle nose pliers in those two holes to the side of the center and back it out that way? Thanks for answering all my questions, I apologize that there is so many of them.

 

[mmckenna]

How do I go about removing it from the outside? Could I stick a pair of needle nose pliers in those two holes to the side of the center and back it out that way? Thanks for answering all my questions, I apologize that there is so many of them.

Yes, give that a try. Don't go white knuckles on it, though. It may have seized up over time.

 

[jim202]

I have always pulled the external bed light off the top rear of the cab. This gives you access to the space above the head liner. Use a metal coat hanger and make a hook on one end that you can snare the old coax cable with. Depending on how it was run, down the post behind the driver or the rear area in the corner. I have always been able to run a small snake down the back corner of the cab and get it coming out under the bottom. You might have to pull loose the molding at the bottom to find it.

 

[cmdrwill]

Yes, give that a try. Don't go white knuckles on it, though. It may have seized up over time.

There IS a proper tool for the NMO mounts. The tool has round tips that fit the round holes in the nut.