Amateur Radio VHF Options

There is one very important caveat to keep in mind when reading this article. The roof of a vehicle is a very good place to mount a VHF antenna. However, more and more new vehicles are coming equipped with side curtain SRS devices. 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. In any case, you should have a copy of the service manual. Typical examples are in the $70 range, and easily pay for themselves when problems arise.

A lot of the material presented here is a duplication of that contained in my Antennas and Wiring articles. Because there are far more VHF/UHF mobile operators than HF operators, and they are similar with respect to installation and safety issues, in a lot of cases VHF/UHF operation present unique problems. For example antenna placement tends to be more critical, and so does the DC power requirements. Hence, this separate article covering these unique differences.

One of the most common mistakes new comers make is in the selection of their mobile antenna. For some reason, 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. It makes very interesting reading even if you don't know how to interpret the included graphs, because the text tells the story.

What's more, if you don't know what the gain figures are measured against, they mean absolutely nothing. One manufacturer's fine print states their gain is measured against the average HT antenna; in other words a rubber ducky. Sure puts new meaning in the term dBd!

Exaggerated claims don't stop with gain figures. One import antenna's manual clearly states it has (sic) two phasing coils, too increase gain. The real truth is, one of these "coils" is nothing more than a coupler used to connect the two upper portions of the antenna together. Smack one hard enough with a low-hanging limb, and your antenna will be no more. Do this with a quarter wave whip, and all you'll do it bend it. A little straightening and you're back on the air.

The other is a coil, wound with what appears to be #24 wire. This more than likely accounts for its low power rating. On top of it all, the NMO style mount most import antennas use, are not compatible with a genuine NMO (New Motorola, shown right) mount. Adding even more insult, they are typically over priced, and their sturdiness is in question, especially those that use SO239 mounting methods.

In urban areas where higher angles of radiation are preferred, you're typically better off with a lower gain antenna. If you're living in an suburban or rural area, gain antennas might have a slight edge. It all depends on the HAAT (height above average terrain) of the repeater being used with respect to the mobile station's HAAT. In Denver, Colorado and other mountainous areas, you're better off with a unity gain antenna (1/4 wave vertical) as the repeaters are much higher in elevation.

My personal V/U antenna is a Larsen NMO2/70 (see photo at left). It is currently the most popular dual band antenna sold. It is rugged (I've had mine on 6 different vehicles), it's rated at 100 watts continuous RMS, 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. The aforementioned 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. I used to run 160+ watts out mobile to a Larsen NMO150. Due to the high power heating the whip, it was necessary to change the whip about every 6 to 8 months. Don't kid yourself; high output power levels require 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 bander which replaces a stock AM/FM antenna. It does not exhibit any gain, so its only attribute is stealth. If stealthiness is worth $400+ to you, go for it!

There are a few clip-on window-mounted ones from companies like MFJ, but they should be used as a last resort. They're passable for rental vehicles I suppose, but I sure wouldn't use one as a permanent install.

Virtually every vehicle made today uses passivated 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. It's this latter property which makes glass mount antennas nearly worthless, as they rely on capacitive coupling. 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. In fact, the coax does the majority of the radiation. Larsen, the largest maker of glass mounts, has information here about mounting them on passivated glass. The best advice I can give anyone about using glass mount antennas is this; don't!

Antenna mounts are another area of contention. Far too many folks just won't drill a hole to properly mount their VHF antenna, much less their HF one. One of the more popular solutions to not drilling a hole, is the Diamond K400. Here's something to consider. The mount in its various configurations, comes equipped with a 2 meter (about 6.5 feet) long piece of what appears to be RG174. That short length adds nearly 2 dB of loss on 2 meters, and 6 dB of loss on 70 centimeters (440)! So much for all that advertised gain by the import antenna manufacturers!

If that wasn't enough, every time you open or close the door or trunk the mount is attached to, the grip loosens with predictable results. And that isn't all! Click on the right photo to enlarge it. The damage you see is all too often the result of using a lip mount. I can assure you, this sort of damage is much more costly to repair, than a simple, 3/4 inch hole.

By far the most longest-lasting V/U mount out there is the NMO (new Motorola, shown above right) 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's for a cell phone.

The special NMO type mount shown right, 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.

SO239 mounts (shown left), the 5/16 inch Antenna Specialists stud mount, and their snap-in 3/8 inch mount should be avoided if for no other reason than they are not waterproof, not to mention their lack of sturdiness. Since the coax comes straight out of the mount instead of at a right angle like the NMO, they are not suitable for over headliner use (roof mounting). By the way, note the weather cap in the left photo.

Mag mounts are an enigma as most people buy them so they don't have to drill a hole in their precious new vehicle. Well, allow me to enlighten you on a well-known fact. Mag mounts 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. And just wait until you hit something hard and the antenna dislodges. In February of 2004, a bystander was struck and killed by a flying mag mount. 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.

If you don't have the proper tools (like the one shown) to install an NMO, or any mount for that manner, be it in the roof or the trunk, I have a good suggestion; go to your local two-way radio dealer. For a nominal fee they'll install the mount in about 20 minutes, and if you want them too, they can also install the power wiring. One local shop here in Roswell, will do both for about $50 depending on the vehicle.

Roof mounting of V/U antennas is always best, but on vehicles with sun roofs and/or side curtain SRS devices, it can be a problem. Trunk mounting is second best, but if your vehicle doesn't have a trunk, the front fenders or cowl area are alternatives.

As a side light, Walt Bordett, N2IK, suggested using the Antenex saw for drilling holes through the firewall for running power cables. This is an excellent suggestion, and one I had never thought of. Thanks for the tip Walt.

If you have a Dodge Ram PU, it is difficult to mount antennas in the roof due to the double, corrugated construction. Here is a hood mount that will work on the Ram. Please note; 2006 and later Dodge Rams and Dakotas require a different bracket than earlier models.

If you're into APRS, Larsen has a new mount just for the purpose. It's the NMOHFGPS. It mounts in a 3/4 inch hole, just like a standard NMO, but has two very interesting features.

First, the GPS antenna is built in as part of the assembly, and is available in several connector configurations. The NMO portion is actually two mounts in one. By simply removing the center contact, and sleeve assembly, it converts to a coaxial mount designed to provide low insertion loss at SHF. Thus, virtually any NMO-based antenna, from 27 MHz, to 6 GHz can be used. While not inexpensive, it allows one hole to act as two.

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Transceiver Mounts

Just about every kind of transceiver mount you can imagine, is made commercially. The Mounts article contains links, and descriptions to many of them. Decent quality mounts are not inexpensive, and for good reason. They have to be sturdily made, and designed to correctly fit the many different transceivers on the market.

The Ham Radio Innovations mount shown at left, is a typical example. Variations are available for just about every current mobile transceiver made, whether it be VHF or HF. They even do custom work.

Some might ask why they need a different mount, when their radio already came with one. Simply looking at the supplied mount will give you the answer. They're made to attach to the head and/or body of the transceiver, but no provisions are made to attach it inside the vehicle. Remembering that the radio's controls needs to be easily reached, yet out of the way of SRS devices, and vehicle controls, it is easy to see why so many amateurs opt for a custom mount. It pays to be safe than sorry.

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Most V/U antennas come with RG58, solid dielectric coax. At V/U frequencies long lengths of it are indeed lossy. At the lengths we deal with in mobile applications, the loss isn't significant. The few tenths of a dB savings RG8 would give over smaller coax, will not suddenly make your signal heard an extra 50 miles. I should add, that coax cable smaller than RG58 (RG174 is an example), should be avoided, especially at UHF. It is interesting to note (as alluded to above), that several Pacific rim manufacturers hype their gain figures, and then ship their antennas with mounts equipped with RG174.

Some antenna manufacturers' installation kits contain RG58/U, which has a solid conductor center. If yours was, replace it a stranded version or you'll end up with an open circuit, sooner than later.

Foam insulated coax, RG8X for example, requires special care. Remembering that the interior of a closed vehicle can exceed 160°F when parked in summer heat, the bend radius shouldn't be less than 3 inches to minimize migration of the center conductor under these extreme conditions.

Lastly, take time to install your connectors properly. An open antenna circuit is just as bad as a shorted one, and improper connector installation can cause both scenarios.

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SWR

Setting the Standing Wave Ratio is an important installation procedure, but not one to fret over afterwards. Unlike the HF bands, most VHF antennas will cover the whole band segment without the need to retune. That is to say, the SWR of an NMO2/70 will be low across the FM portion of the respective bands. Thus the need for an in-line SWR bridge is superfluous. If you're going to operate on the SSB portion, you shouldn't be using a vertical antenna anyway.

Let me make an important point here. If your mobile vertical antenna will cover all 4 MHz of the 2 meter band (or 70 cm) with a low SWR, you need a better antenna and/or installation! This statement is pointed directly at the cheaply made import antennas. The reason for their bandwidth is simply because their overall losses are high.

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I wouldn't recommending a brand or model of V/U transceiver on a bet, as there are just too many different ones to choose from, like Icom's IC-2720 at left, and their V8000 on the right. While I won't recommend one, I will make a suggestion or two up front.

First, never buy a handheld as a first (or only) radio. Most are FM only, and even if they have AM or SSB capabilities, they are severely limited in these modes. All the extra features like weather alert, aircraft frequency coverage, and extended receive are superfluous to the majority of the users.

Secondly, don't limit yourself to an FM only as your first radio, like Yaesu's FT-1802 at left. An FM only capability also limits your scope of amateur radio, and squelches your desire toward upgrading (pun intended).

Further, don't let anyone talk you into a specific transceiver. Remember, it's just like choosing a vehicle. You need to choose the one that meets your needs, not theirs! If at all possible, go to your nearest dealer and play with the various models, like the Yaesu FTM-10Rb (right photo). By the way, the FTM-10R is the first mobile transceiver with Bluetooth capabilities, but it isn't the only one. While Yaesu seems to be leading the charge for Bluetooth, the handwriting is on the wall. Here's more information on Bluetooth.

Dual band units seemingly have replaced most mono band ones. Some are remotable, some not, and the power output runs from 10 watts to well over 75 watts. Most are FM only, but a lot of them are multi-mode (SSB, AM, etc.). To be honest, there isn't much difference in specs between any of them except in the eyes of the beholder. It is the ease of operation which is most important, especially when they are operated mobile. Keep this in mind when making your choice.

Virtually every V/U transceiver out there has sub-audible or digital squelch built in, and most have both. If you have a choice, buy both. There is a large number of repeaters using sub-audible encoding, and the number using digital encoding is growing. If you don't need it now, you soon will. This goes for Icom's D-Star as well. If you can afford it, buy it, as digital communications are the wave of the future. That's an Icom ID-1 in the photo.

If the new-wave of miniaturized radios have a drawback, it is their menuing system. It's tough enough programming them when you're sitting still, much less underway. What's more, most owners manuals are written by engineers, and then poorly translated. This shortcoming can be addressed by going to Nifty Accessories. Their Radio Cards and Mini-Manuals are concise, and easy to read. Prices range from $5 to about $25 which is very reasonable considering their worth.

Remotable transceivers have become all of the rage these days, and for good reason. The number of safe and convenient mounting places in today's vehicles are scarce at best. Remote control allows the main part of the transceiver to be placed under a seat, or in the trunk. Where ever you place it, make sure it has adequate ventilation. Remember, a 75 watt out radio has to dissipate about 85 watts of heat during transmit. Avoid hanging it under the package shelf as this is one of the hottest places in a vehicle. One attribute to keep in mind while your researching your purchase is where does the microphone attaches. If it is on the main unit (like some Kenwood models) rather than on the head, you might want to rethink your purchase. Long microphone cable runs can cause problems.

Stick with the factory microphone! Most all of them are semi noise canceling, and the internal deviation and audio adjustments are tailored for them. Replacing it with a power mic is asking for trouble. And please, if you just can't help yourself and replace it anyway, don't use one with a roger-beep. On the amateur bands, this is a sure sign of a lid and will only bring negative criticism.

Some factory-supplied microphones are capable of more than just sending TouchTones^®. Add up and down buttons, function and band buttons, a myriad of other features, and things get dicey. If you have trouble figuring it out in the store before you buy it, think about the trouble you'll have while you're underway? In this case, simple is better.

One attribute missing (thankfully) in most V/U mobile transceivers is VOX (voice operated transmit). If your transceiver has it, please don't use it mobile. Just about the time you get used to it, some road-raged knuckle head driver will elicit a vile comment, and all of your friendly repeater users will know exactly what you're thinking.

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A Note on APRS

D710A Automatic Position Reporting Systems are all the rage, and there are several web sites devoted to it, including this one. The basic requirements are GPS (Global Positioning System) receiver, although some are built in, and (typically) a dedicated transmitter to uplink the data periodically. Ground stations all over the country (planet) receive the data, and relay it to the various web sites via the internet. The Kenwood TM-D710A is a popular radio for such activity. By the way, Icom bias aside, the D710A is about the best dual bander for the money. If you have the earlier model (D700A), and want the capabilities of the D710A, then talk to your dealer first! Why? You don't have to buy an all-new radio, just the head, and you save a bundle.

The big three all have at least one model with an GPS receiver built in, and Yaesu even has a hand held with a GPS option. Whether you use a stand-alone GPS or one built in, APRS has never been easier. Fact is, there are so many variations of the theme, it would take a dedicated web site just to cover the basics. If you really want someone to know where you are at all times, the APRS is for you. I suggest you do a Google search, but be prepared, you'll get nearly 4 million hits!

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FM transceivers present an unique power requirement. For example, a 75 watt output unit like the Icom V8000 draws 15 amps on transmit which is about 6 or 7 amps more than the average current a 100 watt SSB transceiver draws. Obviously wiring size is important, yet the V8000 power cord as supplied by Icom is slightly smaller than size 10 awg. This presents several potential problems which we'll explore shortly.

While I am on the subject of power keep one important aspect in mind. All major manufacturers rate their power output when the transceiver is supplied with a nominal 13.8 VDC. In the real world, mobile power can be anything from 11 VDC to about 14.2 VDC. If you measure the power out of the aforementioned V8000 when the supplied voltage is about 12 VDC, the power out will only be about 50 watts, perhaps less! This points out the need for adequate wiring, and in all honesty, the factory cable may be inadequate for all but the shortest runs. I cover this subject in my Wiring article along with several other important considerations including proper fusing.

If you're a long winded type, I wouldn't run the V8000 in high power. Fan or no fan, this radio gets HOT! I've never measured the heatsink temperature, but after a 2 minute transmission the heatsink gets hot enough that you don't want to touch it. Obviously, they need lots of ventilation no matter the duty cycle. One more comment; 75 watts out (most hover around 70 watts due in part to a low supply voltage) will over heat most import antennas. Poor mounting techniques exacerbate the problem.

One power-related drawback common to almost every VHF transceiver, is there's no auto-off feature. This drives some folks to use existing (switched) vehicle wiring, and that is always a bad idea. Or, they resort to using relays, which is also a bad idea. There is a solution.

The PowerWerx APO3 is more than just a timed (0, 5, 10, 20 minutes), auto off device. There are four pre-programmed voltages (11.8, 12.1, 12.7, 13.05 volts) settings. Properly programmed, the APO3 will turn off, and on, your radio just by monitoring the battery voltage!

It can handle up to 30 amps making it compatible with almost any radio. It comes equipped with Anderson Powerpole connectors, making wiring simple, and quick! At $60 (MSRP) it is also affordable. Visit their web site for more information.

There are several important things to remember about running high power V/U operation. One of these is safety! As we go higher in frequency and power, the distance you should be away from the antenna goes up. When I was using a 160+ watt power amplifier on two meters through a 5/8 wave roof mounted antenna, you could feel the heat on the side of your face from 5 feet away. While no scientific study has confirmed the dangers, if you can feel the heat it can't be doing you any good! Doubly so if you or one of your friends has a heart pacemaker or similar device. After all, this is how microwave ovens work; they heat food with RF radiation. Recently, the Mirage division of MFJ Enterprises introduced a new line of V/U amplifiers capable of 300 watts output! This brings a whole new level of safety concerns.

It also brings a new level of DC power requirements, to say nothing about antenna power ratings. Looking at this a little deeper, a 300 watt output, solid state amp will input about 600 watts. At a nominal 13.8 VDC, the current draw is nearly 45 amps plus that necessary for the transceiver. If you're planning on running this level of power in your mobile, you need to read my article on Alternators & Batteries, and be ready to buy a second battery. You also need to read my Wiring article if you haven't already.

If you intend to use one of these on FM, you'll need to add a fan to keep the heatsink cool. Even then, you should keep transmissions short. Incidentally, running high power FM in an urban setting is overkill, and may make you a few enemies in high density areas where the distances to the next repeater on the same frequency pair are short. Save it for simplex and rural areas.

If your main use is SSB, it is best to use relay control rather than the built in RF switching. RF switching the units will eventually cause the preamp to fail, and most likely the transfer relay as well. Anyone who has used one of these amps, knows these are the two most common failure modes.

Mirage amps are very popular due in part to their lost cost versus power out. You see a number of these on the used market as a result. Personally, I'd steer clear of the early models as some of the final transistors used in them are no longer available and/or expensive. So, don't buy a used one from anyone without actually seeing it work through a wattmeter into a dummy load.

Later production models are wired for compatibility with their RC-1 remote control. MFJ publishes instructions on how to modify early models to use the RC-1. If you purchase one of these field-modified units, and you do not have the RC-1, the amp will not work even though the on light is lit. It is easy to rewire the amp to original specs, or to build your own RC-1. If you do not have a manual, here is where you can get one. Schematics are not included in on line documents, but you can e-mail Mirage and request one.

Mirage amps, and most other brands, have much lower driver requirements than base amps. An Icom IC-706 will easily over drive any current commercial V/U mobile amp. What's more, most mobile transceivers exhibit a power over shoot on key down. This short duration spike can be as much as 150 watts, even if the transceiver is set for a low SSB output level. Thus, a relay control line is a must as outlined above.

Lastly, if you work on one of these amps, make sure you secure the cover in place BEFORE you attempt to use it! The lid acts as an RF shield, and failure to install the cover properly (all screws in place and tight), could cause you irreparable eye damage! This caveat cannot be over emphasized!

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If you're into operating SSB in the VHF bands, you might want to visit the K. C. VHF Grid Bandits web site. It just proves, for whatever reason, when you're into SSB VHF, you're really into it!

There are still a few autopatches dotted throughout the country, but with the popularity of cell phones, their days are numbered. Nonetheless, most V/U transceivers have touch tone microphones as standard equipment. Nowadays, they are most often used to access mega linked repeaters. It is also a prerequisite for using VoIP in its various forms.

Speaking of repeaters. The Repeater Builders web site offers a lot of information of interest to any VHF operator. Mike Morris, WA6ILQ, and the group have assembled quite a data base covering both GE and Motorola repeaters, and all of the accessories which go with them. If you're into VHF operation, it's a great resource.

If you own an Icom IC-7000, be aware the supplied HM151 mic will not do live TouchTones^®. Instead, you have to preprogram the codes into memory, and there are only four. If you need live TouchTones^®, you could opt for the standard touch tone mic. Or, if you're adept at building minor accessories, you might look here Pipo Pads. They have models to suit just about any need.

Most of the repeater and linking equipment are owned by individuals with amateur radio clubs a close second. All of this equipment, and the time and expense needed to keep them running is not an inexpensive proposition. If you use any facility on a regular basis, you need to help support it. When I was traveling extensively I paid dues to five different clubs so I could use their repeaters.

There are times you shouldn't use any of your mobile facilities. If the distraction is too great with respect to traffic, passengers, or the weather, hang up the microphone and pay attention to your driving.

I have never had a problem with my wife telling me no to that next installation. Those amateurs who use their wives as an excuse for not properly installing mobile radio equipment shouldn't be considering mobile operation in the first place. I have said many times before, the phrase throwing the rig in the car and taking a trip has no merit. Take the time to do it right and you'll never have a problem. Do it hurriedly, make a mess of it, and I'll guarantee your wife will unglue. Think about it.

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