Setting Up

Installing the Radio

Okay, you've collected your bits and your tools and you're sat in your car - what do you do first? You will have to decide where you are going to put your radio. The main thing to consider here is safety. You do not want to put the radio in a place where it or it's cables can interfere with your handling of the car. Remember that you will have to route the cables in a safe way to the radio. Also, you do not want to put the radio where someone can catch and injure themselves.

The second point to consider is convenience. You want to put the set where you can easily read the displays and adjust the dials. This also affects safety. If you have to perform a cross between Yoga and origami to turn the volume up, you are not in safe control of your vehicle.

If you are doing a permanent installation, you will probably want to place it somewhere under the dashboard. If that's the case then you will need suitable brackets and some self-tapping screws. Make sure that when you are screwing in the brackets that you know what is behind the panel that you are screwing into and that you do not screw through something important.

If you are doing a temporary installation, one that you can set up before an event and remove afterwards, then you could simply place the radio on the passenger seat. If you're going to do this you may find it useful to build a cradle to fit it in. The reason for this is that quite often the radios have the speaker fastened to the underside of the case for when the radio is fastened under the dash. Unfortunately, when you place your radio on the seat, the speaker is severely muffled.

Safety is just as important when you are doing a temporary installation. The cables still need to be routed safely so that the do not trip up anyone. Also, where you decide to rest the radio must be reasonably secure. If the set falls off the seat while you are driving, it will distract your attention.

Connecting the Power

Okay, now that you have the radio installed, you will need to provide it with power. If you have a Cigar Lighter plug on the end of your cable then all you have to do is plug it in and away you go. If you are doing a permanent install, you will need to find a suitable power supply.

To do this, you need to decide whether you want the radio to be powered all the time, requiring you to turn it on and off, or whether you want it to behave like your normal car radio and go off when you remove your car key. If the second option is what you're after, then you will need to find the cable that feeds power to your radio. To do this, look at the back of your normal radio for a red and black pair similar to the ones on your set - they will probably be part of a collection of wires going into one large plug. [1] To complicate matters, many modern radios have two power supply leads, one permenantly live and one that is switched by the ignition. This second live wire is used by the anti-theft security feature in these sets that require a PIN number to be entered before the set can be used if it has been disconnected from the battery. However, it does provide us with both types of power lead in an easy to find place.

To find out which is which, you will need a circuit tester. Cheap testers are available for only a few pounds from most car or D.I.Y. shops. They look like a small screwdriver, with a bulb in the handle and a wire coming out of the end. Usually there is a clip on the end of the wire. If you cannot get hold of a tester, two small pieces of wire and a bulb will do just as well.

To use the tester, clip then end of the wire to a suitable earth wire, or a bare piece of car body. With the ignition turned off, insert the end of the tester into the plug for each red wire, making sure that the tester touches the metal pin. If the bulb lights up, you have found your permenant power lead.

Now turn the ignition to position 1 and repeat the search. This will find you the wire that is controlled by the ignition. If you do not find a power lead then you probably have one of three problems: either the bulb in the tester is faulty, the earth wire on the tester does not have a good connection, or someone has stolen your battery.

If you want the radio to have power all the time, and your car radio does not have two power feeds, then you will need to find a suitable lead elsewhere. One way to do this is to follow the leads from the ignition switch itself. This is a slightly more complicated bit as it varies from car to car. You may need a manual for this.

Obviously, if you choose the option of controlling the radio with the ignition key, the power switch on your PMR radio will still work, but the radio will only operate when the radio and the ignition key are turned on. In this way you cannot accidentally leave the PMR on when you leave your car and return to a flat battery.

Once you have chosen your lead, you need to attach the red wire from your radio to it. There are a number of different ways of doing this. A number of connectors have been designed for this job, or you could cut the wire, and use a terminal block to re-connect it with your wire inserted too. In my opinion, the Scotch-Clip^TM is one of it easiest. These little clips are designed to be crimped on to both the existing and new cables, breaking only enough insulation on both to make contact. This helps reduce corrosion in both cables by keeping the amount of metal open to the elements as low as possible.

Finding somewhere to attach the black wire is much simpler. You can attach it to practically any earth wire available, or even just attach it to the car body.

Once you have attached both wires, you should have power to your radio. Test this by turning it on. Remember to turn on the ignition if this is required. If nothing happens check both wires again.

Do not try to transmit on the radio yet. Pressing the transmit button on the microphone before you have set up your antenna could damage your set.

When you first turn on your set make sure that all the displays and indicators look okay. In particular make sure that the transmit light does not come on. If it does then you probably have a problem with your microphone. Turn your set off immediately. If your radio transmits before you have set up your antenna you could damage it.

Installing the Antenna

The next step on your road to radio heaven is the antenna. First of all you need to decide where to place it. Then you need to worry about routing the co-axial cable from it to the radio.

When deciding where to place your antenna, you need to consider what is called the "ground plane". The metal body of your car will tend to pull the signal in one direction. For example if you place the antenna at the back of your car the signal will be stronger in the direction that your car is facing. While there are times where this can be useful, in general you want the signal to be transmitted pretty evenly. To do this, you want to place the antenna as close to the centre of the car as possible.

Another point to consider here is obstructions. Although radio waves do not need "Line Of Sight" they are affected by objects between themselves and the receiver. For instance, if you have a large box van where the box is larger than the cab, then the box will block your signal. To get round this, and also to help avoid other obstructions such as building and trees, you will want to put the antenna as high on your vehicle as possible. Putting the antenna in the middle of your roof will probably give you the best performance as you will have an even ground plane with no obstructions.

Bear in mind that the antenna will increase the overall height of your vehicle. This may cause clearance problems going under low structures. If you store your car in a garage then this is particularly important.

Your decisions will of course be governed by the type of antenna base that you have. If you have a gutter or boot (bonnet) mount then your choices are limited. If you are using a mag-mount then you can use any flat metal panel. Curved or bent panels will reduce the magnetic effect and mean that the base will have less hold. One benefit of a mag-mount is that you can reposition your antenna on a per-event basis to make best use of the Ground Plane effect.

When routing the co-axial cable there is only one point to remember and that is safety. Whether you have a permanent or temporary installation you need to make sure that the cable will not get in the way or otherwise interfere with you while you are driving.

SWRing In

All you should have left now is your SWR meter. You will now use this to set up your antenna. At one end of the SWR meter is a socket for you to plug in your antenna cable and at the other end there should be a patch cable. The patch cable goes into the antenna socket on your radio.

As mentioned earlier in this chapter in the section on SWR Meters, the purpose of the SWR Meter is to compare the signal that you are transmitting with the one that you should be. When they match (i.e. you have a ratio of 1:1) you antenna is set up perfectly. We will now go through the steps of SWR'ing your antenna.

Different SWR meters vary in how they look and work, but generally they all behave in the same way. They all have some form of display, usually a needle. Some have two displays while others have one plus a two-way switch to change the mode of the display. They also have a rotary dial. On the ones with switches, it should be set to "Set", on the ones with two displays, look at the display labelled "Set". Now press the transmit ("Push To Talk") button on the microphone. Once the radio starts to transmit, you should see the display(s) move. Now turn the rotary dial turned until the needle reads the "Set" value. Once this is done, either put the switch back the other way or simply look at the other dial. The value displayed is your SWR reading. In a perfect world, the needle will drop right on 1. Anything near 1 is okay, but if it gets up towards 2 or more then you need to make some adjustments.

If you do get a bad SWR reading, slide the antenna a little further into the base and then repeat the steps above. If the reading improves, slide it in a bit further. If the reading gets worse, try sliding the antenna out. Keep repeating these steps until you get the best reading you can. If you cannot push your antenna far enough into the base then cut a little bit off the whip. If you cannot pull the whip far enough out then you're stuck because you can't glue a bit back on.

This can be a bit fiddly and tiresome, but the effort put in is well worth it as the SWR of your antenna greatly effects the performance of your radio. A well SWR'd antenna can go many times further than one with a bad SWR.

Once you have got the best SWR that you can, disconnect your SWR Meter from the antenna and the radio, and then plug the antenna directly into the radio. The SWR Meter can be in a safe place in case it's needed again. That's it! You now have a correctly configured and working radio - happy talking.