Technical, FAQ's

How To Effectively Install A Mobile Radio

Some careful considerations are required to install a mobile transceiver into a vehicle. Below is a list of a few things you should think about before simply throwing the radio into the vehicle.

Getting power to the radio

Possibly the most important consideration is the power source. A quick glance around inside the car and there is the most convenient power source.

STOP, don’t even think about using the cigarette lighter socket, or aux power socket as they are now commonly labelled.

Why not? There are a variety of reasons why you shouldn’t use this handy, already available source.

Probably the most important reason is the current requirement. It is highly unlikely that the socket or it’s wiring can handle the current needed during transmission. While these sockets may be labelled as being able to supply 10 amps or more, it may not be able to supply a high current for extended periods.

Virtually all modern vehicles use the CAN bus system. This system is basically a computer network using the vehicle’s wiring which allows the various ECU’s “talk” to each other.

As a consequence, the radio can pick up unwanted noise through this power source. Of course, it’s also possible that the radio could introduce noise into the wiring, thus disrupting CAN bus communication.

Where should we get the power from? The manual that comes with the radio will most probably advise that connections are made directly to the battery. In fact, most manuals I’ve read to date does recommend this method.

Two very important points to note here are these: Always, always place a suitable in-line fuse close to the battery.

Secondly, connect the ground wire to the point on the vehicle body where the ground wire from the battery is connected as this will prevent the full battery current flowing through the radio in the event of a fault, or accidental disconnection of the earth wire. Do not fuse the ground wire.

How you route the wiring to the battery is a matter of personal choice, but more importantly, making sure it’s safe, use grommets where cables pass through panels etc.

For professional vehicle installers, there is a code of practice (FCS-1362) relating to the installation of radio equipment in vehicles, far to detailed for this page which can be found on the FCS website or you can download a copy.

Choice of mobile antenna mount

What’s the best method of mounting my antenna? You may as well ask “how long is a piece of wire?”

Many factors affect the choice and method of mobile antenna mounting.

The magnetic based (mag-mount) may be the best option for some. While others may prefer to drill a hole and mount it directly to the bodywork which is the preferable method if you plan to use HF.

Alternatives include rail mounts, possibly one of the preferred options if your car has roof bars. The drawback with this method is you MUST ensure the rails are well grounded! Likewise, a mag-mount may also require extra supplemental grounding for use with HF.

Another option worth considering for mobile is the boot mount or hatch mount. Both of these clamp onto the lip of the boot lid or tailgate. They are very similar in design to each other, the major difference being the hatch mount tends to have a greater degree of adjustment.

This is to take the steeper angles often found on a tailgate into consideration.

Gutter mounts are available, again these are similar to the boot and hatch mounts, although these are seldom seen as most modern cars no longer have gutters.

Homebrew heavy duty mounts

heavy duty homebrew mobile mountThis picture shows my method of mounting my mobile antennas. Due to the size and weight of my Yaesu ATAS antenna, a substantial mount is required. I don’t want it flying off the car while travelling at speed.

Like a lot of modern cars, mine is a hatchback with the rear window glass extending to the edges of the hatch. Thus, unless the mount was placed quite low, a hatch-mount was ruled out, likewise a mag-mount.

My solution was to fabricate my own mounts in such a way that when removed from the car, no visible evidence of modification being done.

After some thought, I arrived at a solution agreeable to myself, the main influencing factors being, strength, appearance, coax routing, not damaging the car and most of all, my limited engineering skills & tools available.

In fact, the only tools required to construct the mount are an angle grinder, a file and a drill.

I ended up making a pair of mounts, one for the ATAS, the other for a 2m/70cms co-linear antenna. One mount is placed on either side of the car.

The mount itself is constructed from a length of steel angle-iron. I started by cutting two pieces to size and shape, then proceeded to bolt them back to back to form a “Z” profile.

Holes were drilled to accept the SO239 antenna connector, and also for the bolt to secure the mount to the car. The finished assembly was given a coat of black paint to help prevent rusting.

The car has a strip of trim on each side of the roof with removable covers where roof bars would normally be affixed. The coax from each of the antenna connectors is routed through the hollow channel moulded on the bottom of the trim strips, to the rear of the car.

From here it simply lies in the channel alongside the hatch opening, down as far as the bumper where there is a small drip loop to prevent water ingress, and then into the boot and routed under the trim and up to the radio.

Mounting the radio

Possibly one of the biggest questions in modern vehicles has to be “Where do I put it?” – And with very good reason.

So, where indeed do you put it? Most modern vehicles no longer have large, handy spaces on or around the dashboard into which you can place a radio, as most now have cup holders where a handy pocket would once have been.

Fortunately, modern mobile radios tend to be smaller than their older counterparts, and although some ingenuity may be required, it is largely quite possible to find a suitable mounting position.

A word of caution; wherever you find to mount the radio, always make sure it is not in a position that will cause injury in an accident, or possibly interfere with driving, for example, cables getting tangled in the steering wheel or pedals.

Remote Mounting Kits

Yaesu YSK-857 Remote KitIt must be noted that some models are supplied with detachable faces (heads) which allow the controls to be mounted away from the main radio when used with suitable remote kits.

My mobile radio is a Yaesu FT-857D used with a remote kit, read more here. The kit pictured is for use with a Yaesu mobile radio, and kits for other brands of radios are very similar.

This particular kit includes a plastic bracket for the head itself, extension cables for the microphone and extension speaker, although the extension speaker cable isn’t absolutely necessary as the head has a jack for a speaker or headphones. Also included is the control cable that connects the head to the main radio body.

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