Communication Equipment ......
Some sound advice gained over many years in the
Radio Communications industry......
Communication is often a major concern when travelling
abroad in convoy with a number of vehicles. Because of the ease of availability,
low cost and inadequate advice, CB is usually chosen. Sometimes causing
endless frustration when it fails to perform the required tasks. At its
best it can become a life saver, at worst a liability if it doesn't work as
expected. Sometimes the user just expects too much from the
equipment and has to understand the realistic performance of what they have and
how radio works. Other times it can be down to poor product, badly
installed equipment or a combination of both.
Not long ago I myself had to fit a CB (don't tell
anyone) to my own vehicle as part of the "required" communications on an
overland trip. Its been a very long time since I had anything to do with
CB thank goodness. I was just amazed how BADLY it performed compared to
the commercial equipment we have used over the years.
Licencing can be difficult or even impossible to comply
with in some countries. Within Europe there is the PMR446 band available
which can be quite good, but outside of the EURO zone you may have to take your
chances .....
I have been in the commercial communication radio
industry for 30+ years supplying all types of users from local farmers, heavy
engineering industry and quarries to regional and National Fire Services and
Local Authorities. Their underlying prime requirement is for reliable
communication in harsh environments. ~~~~
THE SAME AS YOUR NEEDS......
- PORTABLES
- Commercial portables are made to transmit up to a
maximum power of 5 watts. Good quality radios like the Maxon SL55
that are built to a military specification will give good performance and
reliability in harsh environment. They are also easy to operate with the
minimum of buttons so cant be deprogrammed or set into odd operating modes by
busy fingers. Some kind of vehicle charger is required and also a holder
to keep it upright for best reception and stop it bouncing around the car.
Sound quality can be on the low side so an external speaker microphone can
improve this. Use an external antenna that will improve range as the
metalwork of the vehicle drastically cuts down the signal.
-
- MOBILES
- Mobiles will usually give better performance.
Most Mobiles are made to transmit a minimum of 25 watts RF power which is
5 times more than the most powerful portable. Operational range will
generally be twice that of a portable but the terrain still may be the main
factor in determining how far the signal goes. Sound quality will be
much better and far louder which will be good in noisy vehicles.
Additional remote speakers can be fitted so the radio can be hidden away under
the seat if needed. No batteries to worry about or charge.
Improved reliability as 95% of all faults on portables are caused by impact
damage (e.g. dropping).
-
- Fit a fixed mobile and carry a portable will give
you the best of both worlds.
-
- What range can I expect?
- Whatever you use, NO radio equipment will operate
through several million tons of rock, hills and around corners of mountains,
so line of sight is what you will achieve in
most cases. However, some equipment is made to a much higher
specification (and costs more) and will outperform in difficult poor signal
conditions where CB has long since given up. When you look inside a CB radio
from a technical point of view, it's clearly built down to the minimum price
possible and as a result is very poor quality both in design, build and
performance. Portables can be removed from the vehicle if its bogged
down and taken to a high point to improve range.
Range is determined by geographical conditions, antenna position and tuning,
and the performance of the actual equipment in use. Open ground gives good
range and hills restrict it. Sometimes the signal will bounce around
hills and ravines but this is a bonus and cannot be relied upon. The subject
of range can be best illustrated as follows. Imagine a scale contoured model
of your locality, with a small but powerful lamp fitted to the top of your
antenna mast. Areas on the model illuminated by the bulb, will be in the
service area. Shadows will give reduced or no coverage and this gets
worse as you travel further way.
- Antenna efficiency and location
are other factors affecting range. High power (5 watt) hand portables,
fitted to efficient external antennas, will have nearly the same range
as 25 watt mobiles. A mile or two in towns to up to 10/15 miles in open
country. On portables fitted with small flexible integral antennas,
range by comparison will be limited to under a mile in towns and cities to up
to 4 miles in open county. If you are a 1000ft up, you may well achieve
quite amazing range and performance but Murphy's Law says that when you need
it most, you will be bogged down at the bottom of the terrain. But
remember, if you need to contact someone over the other side of the hill, find
a high spot to work from and you may make contact. Using a another vehicle to
relay information will work if good radio procedure is used.
Shouting into a microphone is not the way to transmit a clear signal and only
makes things much worse. Most radio microphones are quite sensitive and the
radio will just compress your speech, the transmission will be no louder and
will probably be distorted and unreadable. If communication is poor,
speak slowly and with a normal voice. Using a normal voice as if you were talking
to someone a couple of Mtrs away will give the best results. Get to know
the phonetic alphabet as this can really help in poor signal conditions.
- Its not just the transmitted power that's important,
the receiver and antenna must be as efficient as possible and that's where a
lot of low cost equipment fails to perform. Reliability
when subjected to dust and vibration is another factor that will affect the
performance of some equipment.
-
- Fixed or installed ?
- The use of fixed mobile equipment is available up
to 25 watts will undoubtedly give the most favourable performance and
reliability and should be used if possible. Fixed equipment is not available
in PMR446 format. However fixed equipment is prohibited in some
countries so the main choice for most people will be a portable of some kind
that can be discreetly hidden from view. A vehicle mounting holder so
the radio is upright, not bouncing all over the cab and onto the floor, with
the Antenna clear of the dashboard (most dashes
contain a thin metal skin that will detune the antenna)
will improve things no end. This should
also include some form of intelligent charging system. If possible use a
radio that permits the connection of external body fitting or magnetic mount
antenna. This will usually increase range by a factor of 4 or more.
It is CRITICAL
that the antenna is TUNED and fitted
correctly to the frequency you are using. See
later notes and advice.
Using a plug in hand Mic / speaker combined unit
will save wear and tear on the charging contacts of the holder and also save
removing the radio from the charger so resetting the charge cycle. Highly
recommended if an external antenna is used to save continual flexing of the
coaxial cable leading to intermittent transmission problems.
- Installation
- A few basic rules regarding installation of
whatever equipment you use.
- Always take the power direct from the battery via
a SUITABLE fuse (10Amp) direct to the radio equipment.
- Use heavy DC cable of 16A rating for the main
supply of mobiles.
- Ensure you have a
GOOD earth on the base of the Antenna if using a
body mount. Check its good with an SWR meter that is made for the
frequency to be measured.
- Make sure the antenna is
clear and free from adjacent
metal work that could detune it such as roof racks etc. This also means
other radio aerials such as the existing fitted radio. As a guide,
nothing should be nearer than within 50% of the
length of the antenna.
- Make sure the aerial is
tuned to the frequency you
are using with an SWR meter made for that band.
CB SWR meters WILL NOT WORK and give inaccurate
results. DON'T take it for granted it will be right !
- Don't coil up
spare coaxial cable. This can be the cause of poor unpredictable performance
as the coil acts as an inductor and may detune the signal. Cut the coax to the
length needed (+ a bit for remaking up broken plugs) for best efficiency.
Make sure its not trapped or crushed by vehicle fittings.
- If using a magnetic mount, try to ensure the
cable is not damaged where it enters the vehicle. Damage can lead to
water ingress into the coaxial cable causing very high losses in performance.
Summary of the 4 types of equipment commercially
available in the UK.
- Portable and vehicle mounted radios operating on
27Mhz Poorest performance,
lowest cost
- Licence exempt low power PMR 446
Good top end products. Modest cost
- Private licensed professional equipment
High quality and best performance. Higher cost
- Radio amateur equipment
Good performance, Complicated, Modest cost
CB is built down to a price and is of poor build
quality and indifferent performance. It is almost impossible
to achieve an "efficient" antenna due to the relatively low frequencies (27Mhz)
that is manageable in size that wont get damaged. Vehicle mounted radios
are limited to 4 watts (illegal high power amplifiers can be obtained in an
attempt to overcome the inherent shortcomings) and with inefficient antennas,
range is still very poor. A mile or two if you are lucky. The CB portables
are even worse, some have long telescopic antennas over a Mtr in length which
are prone to damage and RF power output is extremely low. A few hundred
Mtrs if you are lucky. Audio quality ranges from poor to downright awful.
Different channels are used on the continent to the UK. NOT
RECOMMENDED but OK for the kiss to play with !
Licence exempt PMR446 was introduced 4 years ago
and is now widely used in the UK and is APPROVED for use in most Euro
zone countries. With a few exceptions, radios are of the portable type.
At the bottom end of the market are miniature portables aimed at the
leisure market and available from Dixon's / Argos that are suitable to
give the kids to play with and have a range of a few hundred metres or less.
Best left in the shop for your type of use. Over that last few years some
companies are producing professional quality PMR446 radios. These
are often derivatives of the professional equipment with some
specification changes. Some have military specification approval like the
Maxon SL25 and some
Kenwood and Icom radios. Quality and performance are usually quite good at
the upper end of the market. Power is limited to .5 watt ERP (Half a Watt)
and is only UHF 446Mhz. Range for the better units can be up to 2 to 4 miles.
Antennas are fixed and no external connection can be made to the set.
(Some radios can be modified to increase the power output to 5 watts and
have the antenna modified to take external connections. Technically this makes
the radio un-approved bur does improve performance. Unlikely to be a
problem outside the UK) External
microphones are available for most makes. GOOD VALUE / PERFORMANCE AT TOP
END OF THE MARKET
Licensed Land Mobile equipment is built for
professional use day after day and to a much higher standard. Depending on
the licence, mobiles are available up to 25 watts and portables
(Maxon SL55)
usually are up to 5 Watts transmit power. Available in VHF or UHF formats.
In rural environments VHF 145/175Mhz will usually out perform UHF 400/470Mhz.
For both these frequencies it is possible to tune quite efficient antennas that
are not too large to fairly discreet. For VHF efficient
antennas about 12/18" and UHF about 6". Simple to operate,
fixed pre-programmed channels and good speech quality are key points.
No matter what you press on these radios you cannot interfere with the
programming which is part of the approval. Some form of licence is required
to use this type of equipment in the UK *. If you choose to have your own
radios a "UK General" licence from OFCOM
costs £60.00 for 3 years for up to 10 radios. Other types of licence are
available. (SEE
additional pages for licencing) *For OUR customers we can
issue a temporary licence that will be valid for up to 12 months in the
UK. The MAXON SL55
radio is one of the best selling radios in the UK and has been selected after
extensive trials by a large number of Regional Fire and Rescue Authorities.
We use the MAXON SL55 radio for our own extensive hire fleet to industry.
RECOMMENDED BEST BUY
- THE MAXON
SL55 IS THE RADIO WE WILL BE SUPPLYING FOR ATLAS EXPEDITIONS
THE MAXON PM160 OR
TAIT T8115 IS THE VEHICLE MOUNTED RADIO FOR ATLAS EXPEDITIONS
Radio amateur equipment is usually well built
and offers very good performance and at reasonable cost. The down side for you
is, it is made with complex displays and dozens of complex functions. Most
popular is the 144Mhz or known as 2Mtr equipment. It is only approved for
licensed amateur use who guard the illegal use of their channels zealously. They
even run competitions to see how fast they can locate and direction find (DF)
illegal transmissions !!. The equipment is built and squarely aimed at the
market for the technical user. The more complex the better, with lots of bells
and whistles and many programmable functions is what the amateurs want.
99% of the features on this type of radio you will never use. The chances of
incorrect operation by inadvertently pressing buttons is highly probable in the
hands of the technically challenged or merely by accident. Weird
combinations of selected functions sometimes can only be resolved by a
factory reset losing all your pre-programmed channels.
Result no communication !!.
NOT RECOMMENDED
FOR MOST USERS
In essence,
KIS :-
Keep
It
Simple,
rugged and buy the best you can afford.
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