Mobile Lip Antenna Mount recommendations?

[threeofnine]

I need a recommendation for a good lip antenna NMO antenna mount for a car trunk. I was using a Midland MXTA27 mount and it fit perfect. The only issue is reception was terrible with it so I removed and returned it. I am currently using a Larsen mag mount but I know mag mounts tend to cause significant paint damage if used long term. I would greatly appreciate a recommendation.

 

[n3obl]

Are you sure its the mount. That mount looks just like a laird / maxrad lip mount. Your antenna gonna be the issue.

 

[threeofnine]

Are you sure its the mount. That mount looks just like a laird / maxrad lip mount. Your antenna gonna be the issue.

I believe it’s the mount because I am getting much better reception with the Larsen mount. I used the same Larsen antenna with both mounts.

However, with the midlands mount, I was using a UHF to BNC adapter. Could that have been the issue?

 

[mmckenna]

I believe it’s the mount because I am getting much better reception with the Larsen mount. I used the same Larsen antenna with both mounts.

Where is the current antenna mounted in relation to the old one?

Location matters. Even if you are using a "ground independent" or "no ground plane" antenna, the ground plane will impact performance. Trunk lip mounts put the antenna off to the side of the ground plane and will absolutely impact performance. The trunk lip mounts usually don't make a good connection to ground unless you really crank down on the set screws and cut through the paint.

However, with the midlands mount, I was using a UHF to BNC adapter. Could that have been the issue?

Even a good adapter will add loss.

 

[threeofnine]

Where is the current antenna mounted in relation to the old one

It was the exact same location.
Midland:



Mag Mount:

Even a good adapter will add loss.

I wonder if that is my issue. Any solution to get around this? I’d really love to make the midland mount work as it’s a perfect fit and imo the right size for my vehicle.

 

[G7RUX]

I would be surprised if the adaptor would add significant losses, unless it was defective in some way.
A magmount capacitively couples to the metalwork it is stuck to, providing a capacitive ground. The lip mount is much, much smaller and usually achieves a ground connection using the clamping screws; you may need to remove a little paint to allow those screws to properly connect to the metal panel, although you can add a bit of wax or anti-rust compound to prevent corrosion. I had exactly this issue with a lip mount for a VHF/UHF antenna and it improved dramatically with a proper connection to the panel.

 

[mmckenna]

I've had bad adapters. I would not rule it out as either the cause, or part of the issue.

Ideally, you want the correct connector on the coax to mate directly with the radio. Usually the challenge for hobbyists is not having the crimp tools to do it.

And, I agree about the ground plane. Those trunk lip mounts rely on cranking down the set screws so they fully bite into bare metal to get a ground. Usually people won't do that for risk of damaging the paint. The mag mount will do a better job coupling with the trunkn lid than an improperly installed trunk lip mount.

Ideally, drill a hole and install an NMO mount, and all these issues go away.

 

[threeofnine]

The problem may be that I’m an idiot who used double sided tape instead of the mounting screws… I am a total beginner at this stuff. I’ll swing by the auto parts store, pick up another mount and really crank down the screws to see if that works.

 

[G7RUX]

The problem may be that I’m an idiot who used double sided tape instead of the mounting screws… I am a total beginner at this stuff. I’ll swing by the auto parts store, pick up another mount and really crank down the screws to see if that works.

You can just remove a little of the paint under the screws so there is a good connection, then give the area a decent coating of anti-corrosion wax to prevent any issues later.

 

[mmckenna]

The problem may be that I’m an idiot who used double sided tape instead of the mounting screws… I am a total beginner at this stuff. I’ll swing by the auto parts store, pick up another mount and really crank down the screws to see if that works.

I wouldn't go that far. Usually companies like Midland, selling to consumers, don't do a good job explaining the requirements. Most consumers don't understand how antennas work, and they know that. They also know that the buyers wouldn't buy their antennas if there was risk of damage.

So, yeah, get those set screws to bite into bare metal and see if that improves performance. It may...

 

[G7RUX]

I wouldn't go that far. Usually companies like Midland, selling to consumers, don't do a good job explaining the requirements. Most consumers don't understand how antennas work, and they know that. They also know that the buyers wouldn't buy their antennas if there was risk of damage.

So, yeah, get those set screws to bite into bare metal and see if that improves performance. It may...

I imagine it probably will; I installed a through-body mount but missed that there was insulation on the inside surface of the steel panel and the resulting performance was awful. Removing the insulation around the hole so the mount could properly contact the steel made a huge improvement.

 

[kk9h]

I have used trunk lip mounts on various cars over the years. It is critical that the ground side of the mount not have any paint between the setscrews underneath the trunk lid and the metal of the trunk lid itself. What I do when installing one is to first install the mount where I want it and tighten the screws. Then I undo them and take it off. Where the two screws left a mark underneath the trunk lid I carefully scrape away the paint down to the metal just where the marks are. A small sharp knife is perfect for this. Next I remove one of the screws from the mount so I can look through the hole and center it **exactly** where I scraped away the paint on that side and tighten the other screw. Then I replace and tighten the second screw to secure the mount. Lastly I use an ohm meter to make sure the shield of the coax makes a circuit with any grounded metal of the trunk lid. This method has always resulted in an excellent antenna installation for me.

 

[threeofnine]

Update. I picked up another Midland mount. Yesterday I filed down the paint in the sections under the trunk where the mounting screws bite down. Now the reception is much better. I greatly appreciate the help and advice I was given.

 

[threeofnine]

then give the area a decent coating of anti-corrosion wax

What brand of wax do you use? I Googled anti-corrosion wax but the only thing popping up is a spray. I assume that is not what I need?

 

[G7RUX]

What brand of wax do you use? I Googled anti-corrosion wax but the only thing popping up is a spray. I assume that is not what I need?

There are a good few options available. Here in the UK we have “WaxOyl” but I believe the US has things like Tetrosyl and Bilt Hamber products…to be honest a decent smear of paintwork wax would probably work well at a push.

There‘s no reason why a spray wouldn’t work and it would be useful for other things too.