N1GY- The simple Approach to Ham Radio
and My Model Railroad Hobby
Some Web Sites for Mobile Installation Info
K0BG.com is a good source for advice on installing a mobile rig in a vehicle. Unfortunately, the links I used to display here have apparently been shut down by the automotive manuacturers who used to provide such information. If anyone wants to read what the big three said back around 10 years ago simply send me an email via the contact page and I will be happy to return your inquiry with the manufacturers data sheets that I have on file. I would happily publish them on these pages but because the info may be slightly out of date and to protect yours truly from an attack by overly sensetive corporate attorneys I would prefer that you ask me for the files rather than put them up here.
My experience with installing two-way radios in vehicles began the way a lot of us began. By mounting a "CB" radio in my car. Of course that was a very long time ago. So long, in fact, that I actually had an FCC assigned call sign with my rig. KQA-4710. Since those heady days over 40 years ago, I have installed radios in everything from RVs to aircraft. That experience has taught me a few things about what to do and what not to do when putting a transceiver in a vehicle. First, of course, is the choice of the radio. Although it is possible, and indeed was done many times years ago, tube sets need not apply. The boat anchor rigs are fun to collect, restore, and even use on occasion, but vibration ensures that tubes will work loose and constant preventive maintenance is not what most of us envisioned for a mobile installation. Beyond that caveat, almost anything is possible.
The first question is what bands do you want to operate while mobile. A Technician Licensee will probably want 2 meters and/or 70 centimeters. A General or Extra Licensee may want to add HF. The choices are almost endless. Once you have decided that aspect, the next thing to look at is the space available in the vehicle. Depending on how the dashboard and/or console are designed in the vehicle, you may want to consider a radio with a remote-able control head. Other questions then come into play. Does the mic plug into the control head or do you need an extension for the mic as well? Where are you going to mount the external speaker? How much power is the rig capable of? In mobile installations, generally, the more power the better. I am not advocating the use of an amplifier, but faced with a very low antenna height, multiple obstructions such as semi trailers and bridges, a 5 watt radio just is not the best choice.
Having chosen your rig, the next step is the placement of the radio, or at least the control head in the passenger compartment. In modern cars, you MUST avoid the air bags at all cost. Drilling a hole through an air bag is dangerous and if the radio is in the path of a deploying air bag it becomes a deadly missile. Generally, that leaves us with the lower center of the dashboard or the console. One must also place the rig so that the vehicle controls are easily accessed and so that the rigs controls are also easy to use. Avoid placement that will take your eyes off the road. This is a really good reason to learn how to use those mic mounted controls such as Up, Down and the other programmable buttons on a modern hand mic.
Now that we have a spot in the car for the control head, or the entire radio, if that is your option, we have to secure it in place. This is definitely not a case of throw it on the seat and go. In an accident, any loose gear will become a major, even lethal problem. Use the bracket that came with the radio or make your own. The options are many. The common point to all of them is to secure the rig so that it will stay put no matter what. If you need to drill mounting holes in the car or truck, make absolutely sure you know what is on the other side of the panel you are drilling into. I mentioned air bags already, but air conditioners, wiring, and other components in your car can be just as expensive to replace. Be aware of the same things when you drill into the floor or transmission hump. Most of the times there are rotating parts like drive shafts and transmissions under there, so beware of using screws that are so long that they interfere with parts of the car. If you choose to use a remote control head you need to securely mount both the control head and the main body of the radio.
Up to now I have not mentioned power. That is deliberate, because wire to connect the radio to the power source is easy to get and inexpensive. An extra few feet of wire is immaterial as long as a few rules are followed. First, use the largest gauge wire you can to connect the radio to the battery. For a normal 50 watt rig, 10 gauge wire is preferred, 12 gauge is absolute minimum. For a 100 watt rig like an Icom 706 or Yaesu FT-100, 8 gauge is preferred, with 10 gauge the absolute minimum. The farther away from the battery the main body of the radio is, the larger the wire should be. Heavy gauge wires such as these used to be hard to find. Now with the proliferation of high power stereo rigs, almost any place that sells audio amps for cars should have these heavy duty wires and the fuse holders and connectors to go with them. The wires should also be secured so that they will not interfere with the operation of the car or drag under it. Keep the power wires at least 12 inches away from the ECU of the car, preferably further and also try to avoid running the wires parallel to the vehicle wiring if at all possible. Most modern vehicles have either an unused grommet through the firewall or another grommet that can handle a couple of extra wires. DO NOT under any circumstance, except perhaps for an HT connect to the cigarette lighter plug. Wire the radio direct to the battery; do not even use the fuse panel under the dash. If you want to have the radio go off when the ignition key is off, use a relay controlled by the ignition to switch the power to the radio on and off. Likewise, do not depend on the car body to provide the return path for the power. Modern cars use a lot of adhesives and plastic in their construction; bypass all the problems and go direct to the battery. In the case of some radios such as the 706, I have found it to be a good idea to put a master switch in the power lead to completely shut down the radio when the car is parked. Modern rigs use power even when shut off, just like your TV at home so the switch is a defense against coming back from a vacation or business trip to find your battery dead. Always put fuses in both sides of the power leads as close to the battery as possible. This is in addition to the ones that the manufacturer of the radio put just outside the radio. If an electrical fault happens in the car, you do not want the starter current trying to detour through the radio. Anywhere the power wires pass through any metal panel they should be protected against chafing with a grommet or other method.
Now that we have power, it is time to think about the antenna and its placement. Do NOT put the antenna on or near the engine compartment EVER. That is a guaranty of RFI. Most vehicle manufacturers suggest the roof as the best place for the antenna, followed by the rear deck lid. The antenna should be centered on the roof or deck lid. Placing it on a fender or at the edge of the roof will skew the radiation pattern of the antenna. If using a mag-mount antenna, and there is nothing wrong with that, avoid running the coax into the car between the door frame and the door. Use the trunk lid instead. The trunk lid gets opened far less than the door so chafing will be less. Besides, if you went with a remote control head and put the radio in the trunk, the coax run will be much easier. Coil the extra coax up neatly and tuck it away safely. If using a mag-mount, be sure to leave enough slack coax inside the vehicle available so you can remove the antenna to the trunk compartment when you take the car to the carwash. Drilling a hole in the roof or deck lid to permanently mount an antenna is fine. Just be aware that this entails taking down the headliner or at least the trim to snake the coax down to the radio. Permanent mounting to the deck lid is much easier; the coax can generally be fed through to the passenger compartment relatively easily. Once in the passenger compartment, make sure that the coax, control head and power wires are out of sight and not in a position to trip a passenger exiting the car. Aside from the possible harm to the passenger, it is guaranteed to yank the coax out of the connector and cause a major repair to the installation.
Before we are ready to use our radio, we need to look at grounding. The radio body should be grounded to the nearest metal part of the car with a braided strap or other suitable material. A thin wire will NOT do the job. If your antenna is mounted to a luggage rack or mirror mount, run a similar ground strap from the base of the antenna to a good grounded spot on the car body as well. Grounding will also give the sometimes encountered RFI from the car somewhere else to go rather than into your transmitted signal. Speaking of RFI, certain models of vehicle are known to have RFI problems, notably Ford vehicles from a few years ago which had severe problems with RFI from the electric fuel pump in the gas tank. Other cars and trucks also have had problems. The manufacturers are largely aware of these and have developed solutions for most of them. If in doubt, ask your dealers service manager to look up any RFI problems with your vehicle and their solutions. I do not recommend doing anything to the car yourself that could void the warranty.
Now we can talk about the final details. Place the mic hangar where you can reach it easily without looking away from the road. Secure all wires and cables with cable clamps and/or wire ties. Make the installation as neat as possible so that you are not only safe, but also proud to show off your handiwork. Install an external speaker the same way and use it. It will make the audio much better. Do a little research on your area and its surroundings and program your radio with the maximum number of repeaters you can. Don't forget to include the simplex frequencies like 146.52 and if possible the local weather frequencies. Make a list of the frequencies in your radio by memory channel number and keep it close at hand in the glove box or your wallet. Before you start this project at all, take a little time and research what your cars manufacturer has available. The "Big Three" have all published guides to installing two-way radios in their vehicles. The ARRL also has material on their web site about mobile installations and even has a book out about the subject.
And finally, remember that while mobile, your first and most important job is to drive the car, not to work on the radio. Pay attention and drive safely at all times, the life you save may be your own.