Clean VHF/CB radio installs

I'm getting the

$50 Midland MXTA25 3DB MicroMobile Compatible Gain Ghost Antenna – 3.5” Tall with 1.5” Base Diameter – Low Profile GMRS NMO Connection

MXTA25 3dB Gain Ghost Antenna....does it need its own ground cable ran to it? I'm gonna be mounting it on my roof rack via a steel mount I had laying around.

 

I had a high SWR with it on the roof rack, so I moved it to the "ditch light" location.

 

Is it a good fit in the dash? I was looking a few months ago and recent postings at that time were saying the only good insert for the center console location was some $60 one that you had to order from Australia and that just wasn’t a viable option to me. If this $20 one from Amazon is good quality I’ll order one ASAP.

 

I had high SWR's with that antenna also, no matter where I put it. Look at the Laird ETRAB4503 it's tiny (3.5" tall). SWR with it was right around 1.4 on my roof rack, and with it hit a repeater 15 miles away (haven't tried farther yet). It's also less expensive. https://www.arcantenna.com/products...obile-mount-metallic-ground-plane-is-required

Even though the linked site says the gain is 5db it's really only 3db by the manufacturer's specs

 

Fits good in my dash, I put it right next to my ECT button. The ones you want to stay away from are the keystone ones. You have to put your own jack into them nd they tend to fall apart.

 

Damn. I ordered the "kit" on Amazon that included the antenna I mentioned along with some other things. I'm just gonna run a ground cable up to the mount and then if I have a bad SWR, I'll ground it and see if that helps it. All else fails, I'll try out that Laird antenna.

 

It's a miracle it works at all without a groundplane.

 

Is a 16-18guage wire enough for grounding these things?

 

A groundplane has nothing to do with "ground". I'm sure that is confusing but it is true. I can make a good grondplane for that antenna with a cookie sheet that is not connected to the ground of your truck at all.

 

Whole roof of the truck is a large cookie sheet to bounce the signal off of.

 

But the base of the antenna is not connected properly to the roof of the truck at RF frequencies. RF and DC are not he same thing. The base of the antenna may be connected to the roof at DC but it's not the same thing.

 

Maybe I'm mistaken, but I checked continuity from the antenna base (threads of the NMO mount that antenna screws to) to the roof and also the hood. Which was 0 ohms. Wouldn't that make them all the same potential and part of the antenna base? It might not be ideal as drilling a hole in the roof for the mount, but wouldn't it still have a ground plane effect? Wouldn't it be the same situation for people who mount antennas to ditch light brackets? They are still getting a ground plane from the hood, but most likely the radiation pattern is skewed because of having no metal on one side of the antenna?

I'm in no way smart with radio stuff just enough to be dangerous. But in the end if it transmits and receives that's a win.

 

So doubling back then....do I need to actually ground these antennas at all - running a wire from the mount to vehicle ground? I am no expert, just trying to get it set up right the first time I do it. Can you provide any additional info on the grounding plane you're talking about? Is that needed? How do you do it etc. Just a noob trying to understand.

 

Incorrect. The power/electrical/DC grounds should all be bonded at the chassis ground to minimize the chance of a ground loop. ARRL’s guidance is spot-on.

RF grounds are another matter entirely.

 

No, you do not need a vehicle ground for the antenna to work. If you drill a hole in a cookie sheet, mount the antenna to it, sit the cookie sheet on a saw horse 20 feet from your truck, and run the coax to the radio in your truck it will work great.

 

When you checked continuity, you were measuring DC resistance which is not the same thing at all. The antennas on ditch light brackets are far from ideal. I'll bet that the power radiated from the antenna is a fraction of the radio's output. Most of the power is wasted. Attaching a Bird watt meter inline would show this power as reflected. The antenna may work if you only need to talk to the truck 1/4 mile from you but that doesn't mean it is operating properly.

 

Using a Greenlee punch on a painted or plated surface will lead to future corrosion problems due to the shear stress in the adjacent metal of the “punch” operation.

The correct tool for the job is what a tool & die maker calls a rotary broach. Larsen’s NMO “hole saw” is a rotary broach. Go slowly and lubricate with cutting oil when cutting … to minimize heat damage to both the metal and rotary broach.

 

Amen, brother! Amen!

The so called SWR meters are the wrong tool - but a very fashionable tool. The correct tool is an in-line watt meter that can measure both forward and reflected power; or, a grid dip meter.

Hint: A 50 ohm resistor will give you a near perfect SWR … and radiate very little RF.

 

Yeah, that's why I use a Bird watt meter. It will show the radiated power and the reflected power. That is not the same as SWR. I have done a little work on desert race trucks and buggies. When they need comms. they better work.

 

would the same work but under the under side of a fiberglass topper? Looking to mount an antenna on the roof and I don’t care about drilling a hole in my topper roof, but it being fiberglass figured it wouldn’t work as a ground plane for the antenna or an I wrong on that?