Two Way Vehicle Mounted Radio Installation Information
When you install a two way into a vehicle, you have three important parts to the process.
Finding a suitable position for the equipment.
This is important for the safety of the driver so that in an accident, the radio will not be a position to injure the driver.
The second consideration is that it is always better to have the radio speaker facing the driver. This will give a clearer received signal and the driver will not have to turn the radio volume up as much as he would have to if the radio is hidden under a seat or deep in the dash. A common short cut sometimes used is to not fix the radio down and to push it under the seat. Not only will the radio be lethal in an accident as it could end up anywhere, the radio will be pulling on its leads as it moves around, increasing the chance of faults & as already mentioned, the received signal will be muffled when under the seat.
Selecting the best acceptable aerial position on the vehicle.
Not only does an aerial have to be tuned to the operating channel, its position will make an important contribution to
the quality of the received signal.
LOW BAND uses a plain whip aerial, normally stainless steel, chrome or black but can also be covered in glass fibre.
MID BAND & HIGH BAND has a choice of aerials. You can use a low gain plain whip similar to the low band
but a lot shorter. If you are using a single channel, the whip length is normally cut to the transmit channel. This is most
important. The receiver will receive on any length but if the whip is a long way off the transmit channel, you get very
bad range and could even damage the radio when you transmit. The second choice of aerial is a high gain, sometimes
referred to as 3db gain aerial. It is a lot longer with a coil on the bottom which is sometimes encased in plastic. this
aerial gives you twice as much signal, this does not mean twice as much range but there will be places that with this
you will get a signal whereas if you has a low gain aerial you would not get a signal.
Some drivers think its best to have a good looking aerial so they choose a short, low gain one. Some driver want the
best thing for the job and so install a high gain.
One draw back with a high gain is that some makes have to be adjusted for the channel but the aerial we supply covers
the whole band without changing the length of the aerial.
UHF BAND is not popular with taxi drivers because of its short range. You can use a plain short whip for this band
or a longer, centre loaded aerial which has a coil, normally encased in plastic, in the centre of the whip.
Ok, not many want to install the aerial in the best position, in the centre of the roof! but choosing the next best position
is nearly as good.
1 is the best position but position 2 is next best. 3 is worst but not so bad if you are using a long, high gain aerial rather
than a short low gain aerial.
When you have a plain rod aerial, the length is dependant on the transmit channel. This graph will help you check your
rod length. Although the graph is for the ideal postition ( aerial mounted on a flat sheet of metal ) techincial, the length
alters when the aerial rod is near a vertical surface, as it may be if mounted at the front of a rear wing, but the difference
is not very great and will not make a great difference.
Click here for a larger version
Installing a Power Supply for the radio
This is very important as doing this wrong could catch the vehicle alight and in an accident, if a passenger is trapped
and the car catches alight as you failed to install the radio correctly, you could put the passenger in very serious danger.
Sadly for the passengers in the UK, whereas most licence authorities do many checks on the suitability of drivers and
also carry out MOT type tests on vehicles (at the drivers expense), hundreds of 'death trap' vehicles carry
unsuspecting customers every day throughout the UK waiting for an incident to happen, because the driver wanted
to save a bit of money on the equipment installation, or he went there because the installation was dirt cheap or they
use a person that thinks he knows about best.
The safest way to pick up power is from the battery. This could help cut out alternator interference as well.
If you attempt to pick up power from the wiring of the vehicle, at worst you could destroy electronics parts such as
the ECU unit of the vehicle, you might find that when you transmit, which draws a lot of current, strange things happen,
such as the stop lights might go on, there is just to many things to go wrong to list, except that the ABS brakes may
fail is another one!!
The feed coming from the battery, ( twin lead red & black is normal) must be fused in the positive connection to the
battery. Depending on the radio but between 5 and 10 amp fuse.
DO NOT THINK A FUSE AT THE RADIO END WILL DO, it will not protect the power lead.
The red & black lead is then routed to the radio position, via the bulkhead. The cable must go through a grommet in
the bulkhead because if it went through a hole in bare metal, over a period of time, the metal will rub through the cable
insulation and short out. It is common sense to make certain that the cable does not fowl any moving parts, especially
while routing under the dash. The cable must be fixed down in places so it does not move. One main obstacle is the
steering wheel shaft. If at a later date the cable falls down and gets rapped around this, when the driver turns a corner
the steering wheel shaft will try and pull all the cable around itself, not only could it stop the car from steering, it would
short out the cable in the end.
The cable must be capable of carrying the correct current. Too thin and it will heat up on transmit and also cause a
voltage drop. A too bigger cable will only become unmanageable but will carry the current ok. A typical cable for a
two way radio is 10amp Red & Black twin which is referred as 32x.2 ( each conductor is made up of 32 strands
of .2mm copper )
Vehicle mounted mobiles transmit up to 5 times the power of a handportable and with a larger roof mounted
aerial, you are always better off using these instead of handportables when good range is required. Working from
a basestation, mobiles can have the range of between 5 and 30 miles, range being mainly dependent on the sitting
of the basestation, 5 miles for a poor location, 30 when the basestation is high up on a hill with the aerial on a tower,
clear of any obstructions.
Mobiles can also be used without a basestation and range is dependent on what obstructions are in between the two
vehicles. Normally you can only work around a town, ideal if you are just starting up a taxi firm, but 4 - 5 miles is
about the limit unless one mobile happens to be up high.
Basestation's are used to either provide a fixed point, such as an office, to contact the vehicle mounted mobiles
and handportables from, or they can in addition provide mobile to mobile or handportable to handportable
The standard basestation gives office to vehicle mounted mobile and handportable contact.
The repeater basestation can also provide set to set contact as well as mobile contact.
All these radios need an Ofcom licence which we can organize for you. If you hire the equipment, you can
operate on one of our hire channels for the first 12 months. Email us for details.
Radio Licence for Press2talk Two Way Taxi Services. A Ofcom licence
We can send you a licence application in the post and help you fill it in because of the technical requirements.
(email us if you want us to)
You can also apply on line here
For normal wide area use for taxi and delivery type companies, apply for a
NATIONAL & REGIONAL
PRIVATE BUSINESS RADIO licence.
For handportables and/or vehicle mounted mobiles operating between each other without a basestation,
anywhere within the UK, apply for a PRIVATE BUSINESS RADIO UK GENERAL LICENCE.
You can not operate a basestation on this type of licence but if you are just starting up a taxi firm using
a mobile to take the calls, this type of operating, passing jobs between cars on the two way radio is a
good way of starting up.