RadioTrap System Technology

There are many Radio systems available, some designed for trap control some general purpose systems.

The clay trap environment is actually a harsh industrial application and demands a rugged product capable of withstanding the elements over a wide temperature range. Therefore features to consider are:

• Range

Range specified on any radio control system is usually the ‘maximum’ or ‘optimum’ Range, however this will only be achieved in ideal conditions.
In practice there is always something to cause a reduction of range, either obstacles / poor environment.
Therefore, choosing a radio system with longer than required specified range is generally beneficial because the actual or true system range allowing for obstacles/interference will be better.

• Waterproof

Water ingress can be either external; rain or being dropped in a puddle, or internal; condensation forming from the moisture already within the enclosure, caused from being left outside in all weathers (which is inevitable!).
Waterproofing an electronic product which requires user serviceability (to change the batteries) presents difficulties, however actions a manufacturer can take are:
1. A good seal around the enclosure: ideally a seal which is deformed when the enclosure is tightened.
2. The Circuitboard should be ‘conformally coated’. This is usually in the form of a polyurethane type varnish.

• Technology

Always use an FM (Frequency Modulation) System, Never consider using an AM (amplitude modulation) . An example of the difference in performance can be see on an ordinary radio, such as a car radio. The difference in quality of sound on medium Wave (AM) compared to FM Stereo is easily noted.
AM systems (also commonly found in car alarms) are cheap and do not perform reliably outside a small local area without obstacles.

Considering FM further, new designs are now employing a technique known as ‘narrow band technology’ This is a higher performing design of radio which provides agreater range and better rejection to interference from other radiuo sources.

Standard FM versus narrow band

Every radio will operate on a fixed ‘carrier’ frequency. (for Europe it is often 433.92MHz known as 433MHz.). The data or signal information is embedded within the carrier.
In Standard FM systems the ‘carrier’ signal actually operates over a spread of frequency e.g. 433.5MHz to 434.5MHz (but centralised on 433.92MHz), this is referred to as the ‘bandwidth’.

In Narrow band FM Systems the carrier operates over a much narrower spread, e.g. 433.908 to 433.932MHz which is a much narrower spread.

The benefit of operating on a narrower band are;

• Interference Rejection

The receiver is only looking at a narrower ‘slot; of the radio spectrum and therefore does not even see the interference a standard FM system will see.

• Distinct Frequency Band

Operating over a narrow frequency spread means that we no longer have to operate at the centre frequency of 433.92. we can design the system to operate at the top end of the legally allowed frequency e.g. 434.5MHz. Up at this top end we are clear of most of the general radio traffic, there is less interference – means greater system performance. (all standard FM wideband systems must operate around the centre freq of 433.92MHz)

• Higher Sensitivity and Selectivity

A narrowband design requires a more complex, accurate circuit based on a crystal control, compared to a standard FM design which uses SAW design, a bi-product of this is that the receiver design is more ‘sensitive’ and more ‘selective’ than a standard wideband design, therefore providing greater system performance from the same power output