Icecobra
FRF Addict
Parts of this are copied or read from other parts of the web and most of it is my opinion or observations..
The roof of a vehicle is a very good place to mount a VHF antenna. However, all new vehicles come equipped with side curtain SRS devices, commonly called airbags. They typically are mounted along the edges of the headliner including the rear seat area if there is one. The wiring to these devices may be routed through any one (or more) of the roof pillars. Extra care is required when installing antennas in vehicles so equipped. If you are the least bit apprehensive about your installation, seek professional help from your dealer. The most common mistake newcomers make (after buying an FM only handheld), is the selection of their mobile antenna. Apparently, the only consideration seems to be the amount of advertised gain; commonly referred to as playing the Gain Game. Trust me on this, there is more to VHF mobile antennas than their advertised gain figures!
Danny Richardson, K6MHE, wrote an article for CQ a few years ago concerning the differences between 1/4, 1/2, and 5/8 wave VHF mobile antennas, replete with modeling graphs. It makes very interesting reading (not really unless your a radio geek) even if you don't know how to interpret the included graphs, because the text tells the story. In short, the mounting location and style, have more to do with performance, than the type of antenna used!
The SO239 chassis connector was designed to mate with a PL259, coaxial connector. It was never meant to be an antenna mount, but over the years several manufacturers have used it, in an apparent attempt to avoid paying royalties to Motorola. As I point out below, SO239 mounts are not waterproof when the antenna is removed, while NMO mounts are. This is an important consideration if you take your vehicle to the local car wash.
Vhf/Uhf antenna is a Larsen NMO 2/70 . It is currently the most popular dual band antenna sold. It is rugged , it is rated at 200 watts dead carrier, and requires no tuning. At ≈$90 with the NMO mount, it is also reasonably priced.
Most of the import antennas are rated from 75 to 200 watts. Where these power ratings come from is a mystery. For example, an Icom V8000 with ≈75 watts out will burn up the average import antenna in due time, so you need to take their power ratings with a grain of salt! Even the venerable Larsen NMO2/70 will get warm during long transmissions at these power levels. Don't kid yourself; high output power levels at VHF requires a lot of special considerations (more on this later on).
There are only a few stealthy V/U antennas. The few readily available are all mono band units, universally poor in terms of efficiency, and they are expensive. There is a special made (read that as expensive), dual band which replaces a stock AM/FM antenna. It does not exhibit any gain, so its only attribute is stealth (thankfully!). If stealthiest is worth $400+ to you, go for it! It replaces your stock AM/FM antenna...
Mag mounts were never intended to be used for permanent installations, yet that's what far too many folks do. The usual excuse is, they don't want to drill a hole, and thus damage their precious new vehicle. The truth is, a mag mount can cause more damage than a hole. They do in fact, scratch the surface they're stuck to, no matter what precautions are taken. The major reason is, the magnets collect all manner of metallic brake dust, and other pollutants. Whether you R&R the antenna regularly, or leave it in place, day-to-day travel causes them to move around, and all of that attracted grit acts just like sand paper thus marring the surface. The resulting damage is often called mooning, after the circular marks left behind. And just wait until you hit something hard and the antenna dislodges. Personally, I won't take the chance, and neither should you!
Here's another interesting fact about mag mounts. The amount of "sticking" force is directly related to the thickness of the steel. When demonstrated in a dealer's showroom, they're always stuck to a much thicker piece of steel than the sheet metal on a vehicle. Adding insult, the outer surfaces of some higher priced vehicles use a composite consisting of layers of steel and plastic, or of aluminum. In these cases, mag mounts will not stick at all.
Virtually every vehicle made today uses passivated glass (sometimes called solar glass). Embedded in the glass are metallic particles which serve several purposes. First, they block most UV rays which lessens fading of the interior trim pieces, and they reduce the heat load. Less air conditioning, better fuel mileage. To a lessor degree, the metallic particles act as RF shield for the digital electronics inside the vehicle. The filtered wavelengths include those used by amateurs, cellular phones, automated toll readers, radar detectors, and GPS devices.
Glass mount antennas rely on capacitive coupling. Both passivation, and the thickness of the glass have an effect on the amount of absorption at the various wavelengths. These facts make glass mount antennas nearly worthless. What's more, glass mount antennas do not have a ground plane under them. This causes the return currents to flow on the outside of the coax, thus the coax does the majority of the radiation. Whether or not any given installation can make contacts using a glass mount antenna is moot. The fact remains, Larsen, the largest maker of glass mounts, doesn't recommend mounting them on passivized glass. The best advice I can give anyone about using glass mount antennas is this; don't!
By far the most longest-lasting Vhf/Uhf mount out there is the NMO (new Motorola) series. With few exceptions every manufacturer has at least one model incorporating it. Virtually every police department in the country uses this mount, and for good reason. Yes, it does require that a 3/4" hole be drilled. But if you take your time to do it correctly, it will never leak even when the antenna has been removed. When trade in time comes no one will care. Just tell them it is for a cell phone.
Special NMO: The special NMO type mount , is another knock-off originally designed to circumvent the Motorola patent. While apparently waterproof, using such a mount locks you into one brand of antenna; not always a good idea, especially if you're into off-road activities.
What to use, my opinion the very BEST place would be in the middle of the truck roof. If you don't want to drill a hole, get a good quality magnet mount like one from Diamond Antennas. A 19 inch quarter wave whip in the middle of the Raptor roof will likely outperform a 5/8 wave mounted anywhere else below the roof line. You could also have the ultimate, and put a 5/8 wave on that mount in the middle of the truck roof. Choosing a side mount can be done, but what I am suggesting would likely outperform it and be a lot more simple and cheaper. I have found that a half or 5/8 wave 2 meter antenna on a pickup truck roof is about as good as it gets for range and coverage on two meters. You'd have to mount a co-linear up there to beat it, and that would be a really tall antenna. What I have suggested is just that, a suggestion, I hope this helps a few people looking for antennas..
The roof of a vehicle is a very good place to mount a VHF antenna. However, all new vehicles come equipped with side curtain SRS devices, commonly called airbags. They typically are mounted along the edges of the headliner including the rear seat area if there is one. The wiring to these devices may be routed through any one (or more) of the roof pillars. Extra care is required when installing antennas in vehicles so equipped. If you are the least bit apprehensive about your installation, seek professional help from your dealer. The most common mistake newcomers make (after buying an FM only handheld), is the selection of their mobile antenna. Apparently, the only consideration seems to be the amount of advertised gain; commonly referred to as playing the Gain Game. Trust me on this, there is more to VHF mobile antennas than their advertised gain figures!
Danny Richardson, K6MHE, wrote an article for CQ a few years ago concerning the differences between 1/4, 1/2, and 5/8 wave VHF mobile antennas, replete with modeling graphs. It makes very interesting reading (not really unless your a radio geek) even if you don't know how to interpret the included graphs, because the text tells the story. In short, the mounting location and style, have more to do with performance, than the type of antenna used!
The SO239 chassis connector was designed to mate with a PL259, coaxial connector. It was never meant to be an antenna mount, but over the years several manufacturers have used it, in an apparent attempt to avoid paying royalties to Motorola. As I point out below, SO239 mounts are not waterproof when the antenna is removed, while NMO mounts are. This is an important consideration if you take your vehicle to the local car wash.
Vhf/Uhf antenna is a Larsen NMO 2/70 . It is currently the most popular dual band antenna sold. It is rugged , it is rated at 200 watts dead carrier, and requires no tuning. At ≈$90 with the NMO mount, it is also reasonably priced.
Most of the import antennas are rated from 75 to 200 watts. Where these power ratings come from is a mystery. For example, an Icom V8000 with ≈75 watts out will burn up the average import antenna in due time, so you need to take their power ratings with a grain of salt! Even the venerable Larsen NMO2/70 will get warm during long transmissions at these power levels. Don't kid yourself; high output power levels at VHF requires a lot of special considerations (more on this later on).
There are only a few stealthy V/U antennas. The few readily available are all mono band units, universally poor in terms of efficiency, and they are expensive. There is a special made (read that as expensive), dual band which replaces a stock AM/FM antenna. It does not exhibit any gain, so its only attribute is stealth (thankfully!). If stealthiest is worth $400+ to you, go for it! It replaces your stock AM/FM antenna...
Mag mounts were never intended to be used for permanent installations, yet that's what far too many folks do. The usual excuse is, they don't want to drill a hole, and thus damage their precious new vehicle. The truth is, a mag mount can cause more damage than a hole. They do in fact, scratch the surface they're stuck to, no matter what precautions are taken. The major reason is, the magnets collect all manner of metallic brake dust, and other pollutants. Whether you R&R the antenna regularly, or leave it in place, day-to-day travel causes them to move around, and all of that attracted grit acts just like sand paper thus marring the surface. The resulting damage is often called mooning, after the circular marks left behind. And just wait until you hit something hard and the antenna dislodges. Personally, I won't take the chance, and neither should you!
Here's another interesting fact about mag mounts. The amount of "sticking" force is directly related to the thickness of the steel. When demonstrated in a dealer's showroom, they're always stuck to a much thicker piece of steel than the sheet metal on a vehicle. Adding insult, the outer surfaces of some higher priced vehicles use a composite consisting of layers of steel and plastic, or of aluminum. In these cases, mag mounts will not stick at all.
Virtually every vehicle made today uses passivated glass (sometimes called solar glass). Embedded in the glass are metallic particles which serve several purposes. First, they block most UV rays which lessens fading of the interior trim pieces, and they reduce the heat load. Less air conditioning, better fuel mileage. To a lessor degree, the metallic particles act as RF shield for the digital electronics inside the vehicle. The filtered wavelengths include those used by amateurs, cellular phones, automated toll readers, radar detectors, and GPS devices.
Glass mount antennas rely on capacitive coupling. Both passivation, and the thickness of the glass have an effect on the amount of absorption at the various wavelengths. These facts make glass mount antennas nearly worthless. What's more, glass mount antennas do not have a ground plane under them. This causes the return currents to flow on the outside of the coax, thus the coax does the majority of the radiation. Whether or not any given installation can make contacts using a glass mount antenna is moot. The fact remains, Larsen, the largest maker of glass mounts, doesn't recommend mounting them on passivized glass. The best advice I can give anyone about using glass mount antennas is this; don't!
By far the most longest-lasting Vhf/Uhf mount out there is the NMO (new Motorola) series. With few exceptions every manufacturer has at least one model incorporating it. Virtually every police department in the country uses this mount, and for good reason. Yes, it does require that a 3/4" hole be drilled. But if you take your time to do it correctly, it will never leak even when the antenna has been removed. When trade in time comes no one will care. Just tell them it is for a cell phone.
Special NMO: The special NMO type mount , is another knock-off originally designed to circumvent the Motorola patent. While apparently waterproof, using such a mount locks you into one brand of antenna; not always a good idea, especially if you're into off-road activities.
What to use, my opinion the very BEST place would be in the middle of the truck roof. If you don't want to drill a hole, get a good quality magnet mount like one from Diamond Antennas. A 19 inch quarter wave whip in the middle of the Raptor roof will likely outperform a 5/8 wave mounted anywhere else below the roof line. You could also have the ultimate, and put a 5/8 wave on that mount in the middle of the truck roof. Choosing a side mount can be done, but what I am suggesting would likely outperform it and be a lot more simple and cheaper. I have found that a half or 5/8 wave 2 meter antenna on a pickup truck roof is about as good as it gets for range and coverage on two meters. You'd have to mount a co-linear up there to beat it, and that would be a really tall antenna. What I have suggested is just that, a suggestion, I hope this helps a few people looking for antennas..
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