Random antenna questions (mobile/vehicle mounts)

[Iceking007]

Hello,

I am trying to figure things out and the more I do the more everything seems a complicated. Everyone around here either mounts on the front fender next to the hood or uses a magnet on the roof.

With regards to a pickup truck installation:

Is a magnet bad because of electromagnetic interference?
Would the trade off so be worse than having it on the fender (vs the center of the roof we a magnet)?
I've been reading that the rule of thumb is 3' from other antennas and GPS receivers; that means even the roof might be not ideal, is the box going to be a viable option?

Additionally I am considering having a CB, VHF, AM/FM, plus most vehicles have GPS now, plus of you add your dash GPS, plus of I add a scanner in the future... how/where/what do you do with everything?

(I'm sorry I've just been very lost lately - in life in general)

I just found out that only the tip transmits the signal, is that the same for receiving?
If the tip contacts the ground plane (also read grinding system) does that create a dangerous short? (If so then I've just been extremely lucky! :::EEPS::: )

At this moment I'm considering mounting a small spring/quick release in the center of my roof for changing vhf tuned top mount antennas, then mounting my 10' whip CB antenna to the left rear corner of the box. The AM/FM is located in front of the passenger.

But I keep going back and forth if I want to drill holes in the roof.

Also, why do highway tractors mostly have all the antennas on the mirrors? If they get decent enough reception does this all really matter??

Also, what about Marine antennas. Perhaps this are fund to a different frequency range, but they look very well built. Could that be used on a truck for vhf?

 

[Project25_MASTR]

Drill holes. I personally have a Panorama Sharkee on my pickup with the tri-band whip. Just me though.

Generally, you want to keep your antennas separated by a 1/4 wave of the frequency of interest. Typically, I'd run VHF/UHF on the roof with CB on a fender mount.

 

[jim202]

Hello,

I am trying to figure things out and the more I do the more everything seems a complicated. Everyone around here either mounts on the front fender next to the hood or uses a magnet on the roof.

With regards to a pickup truck installation:

Is a magnet bad because of electromagnetic interference?
Would the trade off so be worse than having it on the fender (vs the center of the roof we a magnet)?
I've been reading that the rule of thumb is 3' from other antennas and GPS receivers; that means even the roof might be not ideal, is the box going to be a viable option?

Additionally I am considering having a CB, VHF, AM/FM, plus most vehicles have GPS now, plus of you add your dash GPS, plus of I add a scanner in the future... how/where/what do you do with everything?

(I'm sorry I've just been very lost lately - in life in general)

I just found out that only the tip transmits the signal, is that the same for receiving?
If the tip contacts the ground plane (also read grinding system) does that create a dangerous short? (If so then I've just been extremely lucky! :::EEPS::: )

At this moment I'm considering mounting a small spring/quick release in the center of my roof for changing vhf tuned top mount antennas, then mounting my 10' whip CB antenna to the left rear corner of the box. The AM/FM is located in front of the passenger.

But I keep going back and forth if I want to drill holes in the roof.

Also, why do highway tractors mostly have all the antennas on the mirrors? If they get decent enough reception does this all really matter??

Also, what about Marine antennas. Perhaps this are fund to a different frequency range, but they look very well built. Could that be used on a truck for vhf?

You have asked a number of questions, so let me see if I can help clear the air some.

First, on the mag mount, the magnet will not effect the radio reception or transmission. But it will play heck with the paint job over time. There is enough abrasive particles in the air which will do a number on your roof paint job. It acts like fine sandpaper with the wind swirling around the magnet base. Short time use isn't bad, but long use in the same spot will create spots on the roof.

As for what part of the antenna radiates the signal, the entire length is the radiating element, not just the tip. The length of the antenna rod needs to be a length that is resonant at the frequency your trying to transmit on. The SWR is important to keep low to get the most efficient radiation from the antenna in transmit. In receive it is not that important.

As for placement of antennas, the real point to keep in mind is the transmit power your going to use. The higher the output power, the more spacing the antennas need to have between them. This is to prevent damage to the receiver front end transistors that are used as receiving amplifiers. Now you can do some electronic mods to the receiver and put a pair of back to back hot carrier diodes in to prevent damage. I have done this to several of my radios as I use 100 watt transmitters.

As for your 10 foot whip antenna, don't forget that it will hit anything that is low enough. This can be tree branches, low bridges, even the 4 foot or 8 foot long light tubes at gas stations. I can tell you from experience years back, that the station owners get real upset when you clean out some of his tubes.

The 18 wheel tractors use the mirror mounts as the truck owners frown real hard with the drivers drilling holes in the4 truck roofs. I use to service a number of cement trucks that had a low band radio system. But they used the ASP type mounts. Those antenna coils were really rugged. The rods still had the small little balls at the top end of the rod. These rods seemed to like to get caught in tree branches. With the rugged construction of the coils, the result was a roof ripped open like a can opener. I came in and changed the antenna brand to Larson brand and the coils would break off from the base and not cause the roof damage. No more expensive body shop repairs. Just replace the coil and maybe the whip and keep on trucking.

But back to your question, the mirror mounts are easy to install and remove if the driver doesn't drive the same tractor. It only takes a few minutes to swap it to another tractor.

As for drilling holes in the roof, you need to take a little care and investigate the mounting location. Some trucks have a double roof. There are also roof supports you can't see from the outside. So I always open up the head liner so I can take a peek between it and the metal roof. If your only going to mount one antenna, then I would take down the light at the rear window. Normally you can carefully open up the fixture from the outside using a screw driver. It lets you look above the head liner without having to take down the head liner.

They make a special drill bit for making the 3/4 inch hole in the roof without damaging the head liner. It only goes in about 1/4 inch. It has a ridge to keep it from going in too far and tearing up the head liner. Some people go to the extreme of using a chassis punch. But that means you have to be able to get to both the top and underside to use it. Long arms come in handy using this method of making a hole.

The marine antennas are designed not to need a metal ground plane under them. Normally they are of the 5/8 wave length so they will work on the fiberglass roof that most boats have these days.

I think that covers the main questions that you asked. If not, ask again and someone will answer your questions if I don't see them.

 

[mmckenna]

With regards to a pickup truck installation:

Is a magnet bad because of electromagnetic interference?

It can suffer from some issues due to lack of good grounding at the antenna base. But generally a magnetic mount antenna works "OK". Not ideal, but not the end of the world.

Would the trade off so be worse than having it on the fender (vs the center of the roof we a magnet)?

The fender mounts create some lopsided ground plane issues. It can make an antenna a bit directional.

I've been reading that the rule of thumb is 3' from other antennas and GPS receivers; that means even the roof might be not ideal, is the box going to be a viable option?

Everyone's thumb is a different size.
It depends on frequency, power levels, the design of the other electronics.
Sure, 3 feet is great. More can be better but less can work. All depends on a lot of variables.

Not sure what you mean by "box". If you are talking about mounting an antenna on a pick up box, it's going to create issues. Lopsided ground plane, like the fender mounts. Depending on the frequency, the cab can block signals, detune the antenna, expose the people inside to high levels of RF radiation, etc.

Additionally I am considering having a CB, VHF, AM/FM, plus most vehicles have GPS now, plus of you add your dash GPS, plus of I add a scanner in the future... how/where/what do you do with everything?

Not sure what kind of truck you are talking about. Full size, smaller, crew cab, regular cab???

Mounting multiple antennas on the roof if even a regular cab truck isn't an issue.
My work truck is a regular cab F350 with a VHF and 800MHz antenna on the roof. No issues.
I don't have GPS, but again, not an issue. Most good receivers have filtering in the front end that will reduce out of band signals considerably.
Only issue is that scanners tend to lack, or have severely limited, filtering on the receivers. Having a scanner antenna too close to the transmitting antennas can cause the scanner to be overloaded when one of the other radios is transmitting.

I just found out that only the tip transmits the signal, is that the same for receiving?

The entire element radiates transmitted signal. The entire element receives signals.

The little ball on the end is just so you don't poke your eye out.

If the tip contacts the ground plane (also read grinding system) does that create a dangerous short? (If so then I've just been extremely lucky! :::EEPS::: )

It can, but depends on the antenna type. It's not going to cause your radio to explode, though, at least not with any sane power levels.

At this moment I'm considering mounting a small spring/quick release in the center of my roof for changing vhf tuned top mount antennas, then mounting my 10' whip CB antenna to the left rear corner of the box. The AM/FM is located in front of the passenger.

Dead center of the cab roof is the ideal location. You want a ground plane under the antenna in all directions. At VHF frequencies, that needs to be about 19 inches in all directions to give the best performance. Really easy to do that on a truck roof.
My work truck has the two antennas, mounted side by side. Each one is about 22 inches in from the outer edge, centered front - rear. There's a good 26 inches between the two antennas.
You -could- mount the VHF on one side, 19 inches or more in from the side, and the CB on the other side.
You won't have enough room to make a suitable ground plane for the CB antenna, it would need to be about 9 feet in all directions, and you won't get that on a road legal vehicle, so you do the best you can. Getting the antenna up on the cab will give you a bit better performance by putting a slightly better ground plane under it than you would on the rear of the bed rail.

But I keep going back and forth if I want to drill holes in the roof.

Yes, you do.
If you are putting this much work into figuring all this out, why cut corners on the antenna mount? If you are going to use a mag mount, then slap it up there somewhere near the center and get on with life.
But if you want the best performing system you can get, drill the hole. There's a reason why the pro's do it that way.

Also, why do highway tractors mostly have all the antennas on the mirrors? If they get decent enough reception does this all really matter??

They are usually running dual antennas. To get the benefit of running dual antennas for CB, you need almost 9 feet between the antennas. The only way to get that is to put them on the mirrors.

Often it's done because they want the easiest way to install the antenna and don't really care about performance.

Also, what about Marine antennas. Perhaps this are fund to a different frequency range, but they look very well built. Could that be used on a truck for vhf?

Marine VHF radios run in the 156-162 MHz range, so not far off from the 2 meter amateur radio band.
There are different styles of marine antennas, and not all of them are going to work well in a mobile application.
The tall white ones are usually fiberglass, and they won't stand up to tree branches or parking garages. They are usually designed so as not to require a ground plane, since a fiberglass or wooden boat isn't going to have one in most cases.
Some of the shorter stainless steel antennas are half wave antennas that also don't require a ground plane. In a mobile application they might work, but the lack of a spring at the base would cause the stiff whip to cause some damage in a parking garage or low tree branch.
Also, the 1 inch mounts will be a pain to do in a vehicle.

Best bet is to stick with the industry standard NMO mounts. That'll give you the widest selection of antennas.
For CB, I'd strongly recommend the Larsen NMO-27.
For VHF, a Larsen NMOQC tuned for your VHF frequencies would work well.
For your scanner, the Larsen NMO-150-450-800 is a good option.

Stay away from the amateur/hobby grade antennas.

 

[mmckenna]

What make/model/year truck are you talking about? Many of us have done a lot of installs over the years, and may have some experience with yours.

 

[Iceking007]

Wow that's lots of great information.

And I had a lot of very poor grammar and spelling (sorry about that, part of the challenge of cellular telephone typing).

First of all the truck I currently own is a 2010 f150 super crew cab, short box. But have also been considering changing that up.

I am not at all considering a magnetic mount, I was just trying to get an understanding and comparative between options.

I will either go fender or roof. My previous vehicle was a 1991 Ford Explorer 2dr sport. I had my 10' whip on the top of the roof (rear right corner) and my clearance was 4.1m. Often I drove with it up no problem, occasionally I stowed it in an arc over the front of the roof.

I don't think I'll position the CB on the roof; but perhaps I should, I feel I got good reception with the vhf on the fender and the CB on the back corner of the roof. I was considering mounting the VHF on the roof now as it's more crucial to have better performance than the CB antenna but perhaps the CB would benefit the most?

Is it a substantial benefit going to the roof? (Perhaps that's rhetorical, seems that has been answered many times, sorry)

I guess a marine antenna might be a poor choice, although my 10' whip cleared most everything I never had to worry about it because it would just bend and flex, fibreglass as noted won't.

Okay a real question, no more rambling...

Why do 5/8 or 1/2 wave antennas not require ground planes?

Why not only run 5/8 or 1/2 waves then you don't have to worry about drilling holes in the roof?

Thank you.

 

[kjl13]

Have you ever considered a lip mount? And if you are worried about drilling one hole for a nmo mount, they have plugs for them when you remove the mount and sell your vehicle.

 

[mmckenna]

Okay a real question, no more rambling...

Why do 5/8 or 1/2 wave antennas not require ground planes?

Why not only run 5/8 or 1/2 waves then you don't have to worry about drilling holes in the roof?

Thank you.

5/8th's wavelength antennas do require a ground plane to work correctly.
1/2 wave antennas do not, but they do work better with one. Has to do with the way the antenna is fed.

Different antenna types give different types of performance. One is not 'better' than another. Specific antenna types fit specific needs. In some applications, a 1/4 wave will outperform a 5/8th's wave. In other applications, the 5/8th's will outperform the 1/4 wave.

Doesn't matter the antenna type, the mounting doesn't play into that.

 

[Iceking007]

Well that leaves me to do lots of research.

Okay, so someone mentioned about Highway tractors having two antennas for one CB unit. Is it possible or a good idea for a VHF? What if you had an SUV and mounted a VHF antenna on the front left near the hood and then to the rear right near the tailgate?

Thank you.

 

[Project25_MASTR]

Well that leaves me to do lots of research.



Okay, so someone mentioned about Highway tractors having two antennas for one CB unit. Is it possible or a good idea for a VHF? What if you had an SUV and mounted a VHF antenna on the front left near the hood and then to the rear right near the tailgate?



Thank you.

Dual antennas, or more commonly co-phased antennas, is a method to turn radiated signal into a directional pattern. Gives you 3 dB more but more of your energy goes forward and back. Great for tractors running down interstate, needs 9 feet of separation to work marginally right (really, 35 feet is ideal) for CB. You don’t really reap the benefits with VHF since you can more practically obtain a gain antenna.


Sent from my iPhone using Tapatalk

 

[Iceking007]

Okay, so after more thought and planning I have some additional questions.

I have decided to sell my f150 and have been looking at buying a 2008 Toyota FJ cruiser. I am planning on buying a fiberglass VHF antenna and using my 10' whip CB antenna (to start with. I might purchase a fiberglass CB to match the vhf at a later date but I'm thinking the longer antenna will yield better functional results?)

I would like to maintain the functionality of the overhead roof rack storage system so I am not currently planning on mounting any or all antennas in the center. I will most likely build clamp brackets for the edges of my roof rack and use those locations for testing to begin with, in the future and once I get settled into the vehicle I can decide if I need to move things around for better functionality etc.

One question I'm wondering is for antenna order/distance placement. I am curious if I have a roof mounted GPS receiver, roof mounted cellular telephone 3g/4g Rx/Tx, roof mounted VHF, and roof mounted CB; what would be the preferences distance order?

Eg: 3g/4g could be close to the GPS, then your CB then the vhf furthest away from GPS/cell. Something like that so I can decide on their distance separation and roof placement.

I will also keep the vehicle default am/FM antenna mounted passenger A pillar hood area.

I am also curious, is HD video (6G 75ohm) coaxial cable suitable for antenna cable? And is it also required to keep antenna signal cables separate from each other? I have limited options for that also but I could route the crucial ones up each of the the A/D pillars, of course they will be routed separately from power.

Thank you for the advice.

 

[mmckenna]

I am planning on buying a fiberglass VHF antenna

Why fiberglass?

I might purchase a fiberglass CB to match the vhf at a later date but I'm thinking the longer antenna will yield better functional results?)

1. Don't put looks ahead of performance, unless looks is all you care about. Matching the size of the antennas might improve the looks, but not necessarily be a good idea from a performance standpoint.

2. Longer antennas do not necessarily work better than shorter ones. There's some good reasons to have shorter/lower gain antennas.

I would like to maintain the functionality of the overhead roof rack storage system so I am not currently planning on mounting any or all antennas in the center. I will most likely build clamp brackets for the edges of my roof rack and use those locations for testing to begin with, in the future and once I get settled into the vehicle I can decide if I need to move things around for better functionality etc.

Sounds like a good plan. When you mount the antennas off the side of the roof rack, that's going to create issues with the ground plane. For VHF you'll need to use a 1/2 wave antenna if you want it to work well. 1/2 wave antennas can work independent of the ground plane, and would be a good choice for that type of mount.

One question I'm wondering is for antenna order/distance placement. I am curious if I have a roof mounted GPS receiver, roof mounted cellular telephone 3g/4g Rx/Tx, roof mounted VHF, and roof mounted CB; what would be the preferences distance order?

The AM/FM radio will likely get some interference from any reasonable power VHF radio, that will mean the FM broadcast reception will drop out when you key up the VHF.
The cellular stuff likely won't be impacted. Small antenna, usually decent filtering. Still, keep the other antennas a bit away from that. Give it around 2 feet or so.
Keep the CB and VHF antenna separated as much as you can. Since the 1/2 wave whip can be close to the length of the CB antenna, there can be a fair amount of coupling between them. That can make tuning difficult, result in RF from the VHF radio getting into the CB and causing issues like desense, etc. Maybe put the CB on one side of the roof rack, and the VHF on the other.

Eg: 3g/4g could be close to the GPS, then your CB then the vhf furthest away from GPS/cell. Something like that so I can decide on their distance separation and roof placement.

See above. Keeping the VHF, which will likely be running more power clear of the other stuff is good practice. I wouldn't worry too much about a legal CB radio, even a reasonable size amplifier likely won't be much of an issue.

I am also curious, is HD video (6G 75ohm) coaxial cable suitable for antenna cable? And is it also required to keep antenna signal cables separate from each other? I have limited options for that also but I could route the crucial ones up each of the the A/D pillars, of course they will be routed separately from power.

Thank you for the advice.

RG-6 can work. It's a 75Ω cable, and your antennas and radios will prefer a 50Ω cable. Not a huge impact on things, and your radios won't go up in a mushroom cloud of fire if you use it, but the proper 50Ω cable is cheap and the connectors will fit properly. I'd avoid the 75Ω cable. Standard RG-58 is cheap enough.

 

[Iceking007]

Because truthfully I prefer the looks of the fiberglass antennas. I don't like the silver (stainless? steel) ones.

Does a stainless steel antenna work better than fiberglass?

I was also wanting to go with a top load antenna.

So keep the VHF far away from the am/FM and CB antennas, got it!

What about the GPS/mobile? Would those be effected?

So I'm thinking then, mount the vhf drivers rear corner, CB passenger front, and then perhaps the GPS front center and mobile rear center.

That'll give me some decent separation?

Guess I can go out and buy some RG58.

 

[mmckenna]

Because truthfully I prefer the looks of the fiberglass antennas. I don't like the silver (stainless? steel) ones.

Does a stainless steel antenna work better than fiberglass?

A couple of things you would want to consider...
Choosing the antenna material first is going to limit your choices quite a bit. Due to the mounting location, you will need to use a ground independent antenna. That's going to limit your choices quite a bit. Adding the fiberglass requirement narrows it even further.

Also, fiberglass antennas can be problematic on vehicles where tree branch strikes, low parking garages, drive throughs, etc. Even with base springs, the tops will begin to splinter in short order.

Fiberglass vs. stainless… A properly designed antenna won't care what it's covered with. The benefit to stainless whips is that they'll flex easier without taking damage. They are also easier to tune correctly. Proper tuning is important for performance.

I was also wanting to go with a top load antenna.

Priority will be to get the antenna design that will work properly with your mounting location. All the half wave VHF antennas I've seen are going to be a design that includes a base coil and a stainless whip. I've never seen a top loaded half wave. If you really want a top load VHF antenna, you are going to need to mount the antenna on a good ground plane. Antennas that require a ground plane are going to be problematic if you do not provide them with a ground plane.
So, essentially, it comes down to making a choice of 1. do you want it to work well, or 2. are the looks more important than the performance?

So keep the VHF far away from the am/FM and CB antennas, got it!

What about the GPS/mobile? Would those be effected?

I think those will be OK. Frequencies are pretty far removed from where you'll be transmitting. GPS receivers usually have pretty good filtering and can be installed as part of the VHF antenna base. Mobile phone should be just fine.

So I'm thinking then, mount the vhf drivers rear corner, CB passenger front, and then perhaps the GPS front center and mobile rear center.

That'll give me some decent separation?

Guess I can go out and buy some RG58.

I think that'll be fine if that's what you want to do. With the ground independent VHF antenna, where you mount it won't be much of an issue as long as it's up in the clear. Finding a ground independent CB antenna will take a bit more work, but not impossible. But, on the other hand, CB is going to be pretty limited anyway, and most users ignore mounting requirements, ground planes, etc. If you just need it for short range trail use, then don't get too hung up on it.

As for the coax, pick your antennas first, then the mounts. Mounts often include the coax.
I'd strongly encourage looking at the Larsen brand antennas. Larsen has been making professional antennas for decades and have an excellent reputation.
For VHF, consider the Larsen NMO-150HW. It's an NMO based half wave VHF antenna. You can get it with a base spring, which may be a good choice for being on top of an SUV.
For the CB, the Larsen NMO-27 is a proven performer. When I do run CB (rarely) I have a nearly 30 year old NMO-27 that I use. Great antenna, and will easily outlast your vehicle.

NMO mounts are a good choice. They are an industry standard, and you can swap NMO based antennas between manufacturers without any issues. That gives you a wide choice of antennas depending on how your interest change. You can get cellular and GPS NMO base antennas easily.
Most NMO mounts include high quality RG-58 or better cable.

Avoid Tram, Browning, or any of the Chinese brand cable, mounts, and antennas. While they may save you a dollar or two, they are usually of poor building quality. Larsen and some of the bigger name brand professional grade antennas are proven in the industry and will be a good investment. It's worth getting the good components, prevents issues in the long run. The antennas are the most important part of your installation. Cutting corners won't serve you well, and the minimal amount of savings won't pay off.

 

[Iceking007]

Okay, good thoughts.

Guess I'll stick with SS.

I already have the 10' CB so I'll stick with that for now and buy a SWR tuner instead.

I will look for a Larsen NMO-150HW and start there. The cable is a consideration because I will be cutting it to length and for the installation, so I will have to buy my own connectors and such anyways. I'll have to do more research on that.

Thank you so much for all of your assistance. Although I do prefer the fiberglass look I would much prefer hassle free/problem free reliability and to be one who's gear works where and when others doesn't.

 

[Iceking007]

Is the Larsen NMO-150HW just the base?

I see some coming up with no antenna and others listed as 5/8.

What would you run as a 1/2 wave whip in that?

Will a 5/8 or 7/8 be a better option than a 1/2 wave? (those come up on searches)

 

[prcguy]

The Larsen NMO150 series is a 5/8 wave antenna. Some say a .64 wave over a ground plane will give the lowest angle of radiation and following close behind is the 5/8 wave then a half wave. I don't think 7/8 wave is a viable low angle radiator and may have only been offered as a sales gimmick by some CB antenna mfrs.

Is the Larsen NMO-150HW just the base?

I see some coming up with no antenna and others listed as 5/8.

What would you run as a 1/2 wave whip in that?

Will a 5/8 or 7/8 be a better option than a 1/2 wave? (those come up on searches)

 

[dlwtrunked]

You have asked a number of questions, so let me see if I can help clear the air some.
...
But it will play heck with the paint job over time. There is enough abrasive particles in the air which will do a number on your roof paint job. It acts like fine sandpaper with the wind swirling around the magnet base. Short time use isn't bad, but long use in the same spot will create spots on the roof.
...

I drive a 2006 Toyota Corolla that has had a magnetic mount (Larsen's) on the roof for over 300,000 miles (the odometer stops on that model/year at 299,999 miles. There is not a single mark where the magnetic mount is placed. I wash/wax (drive through) every several months and remove the antenna and clean it when I do that. So on a reasonable kept car, my experience is that damage from a magnetic mount is non-existent.

 

[mmckenna]

The Larsen NMO-150HW is the half wave VHF coil, not a 5/8th's wave. You'd need the NMO mount and a whip to go with it.
A 5/8th's wave or 7/8th's wave antenna is going to require a ground plane. Your mounting configuration will not provide a proper ground plane, so you'll need to stick with the half wave design.

I use one of these on the roll cage of a Polaris Ranger UTV. https://www.theantennafarm.com/catalog/laird-technologies-b1442ns-7116
With the lopsided mounting on the roll cage, the half wave helps. I've hit this on tree branches while cruising down trails at 35mph, and no issues other than a slight bend at the very end of the whip.

 

[Iceking007]

Any recommendation on SWR meters?

Is there a benefit to a $300 meter over a $30 meter?

Analog vs digital?

Thank you very much for everything.