Radio communications systems started to appear in the late 19th Century, with pioneers like Marconi sending signals across the Atlantic by morse code.

Soon such systems were being rapidly adopted by both government and industry, as an alternative to the existing ‘Wired’ telegraph systems.

Radio offered advantages over the Telegraph system, due to cheaper infrastructure costs. This is because the telegraph system required the purchase and installation of telegraph wires & poles.

Radio communications, on the other hand, did not require expensive long distance wires, and the installation of many telegraph poles.

Radio proved to be particularly cost-effective compared to the telegraph, for international communications, which required undersea cable installation.

There were some disadvantages of early radio communications systems, however.

One such disadvantage was call privacy, as early radio systems did not use the modern encryption methods available on radio systems today.

This meant that confidential messages could be easily eavesdropped, by ‘Third Parties’.

This was an issue for both government and business users, but modern systems have overcome this.

A famous early example of radio communications use was the ‘Titanic’ ship disaster of April 1912. The Titanic is a state of the art ship that had been equipped with a two-way radio system, which used Morse Code for communicating messages.

As the ship was sinking, radio messages were able to be sent out for help, and it was the first time that the new emergency code ‘SOS’ was used.

Although there was a massive loss of life, many lives were undoubtedly saved due to being able to get the message out to rescue ships in the area that they were sinking.

Without radio communications, the first indication of the disaster would have been, when the ship failed to arrive in New York as scheduled.

In 1922 the BBC was formed in the UK, and for the first time, the ordinary (nongeek) public was able to experience radio. Although public broadcasting is only one way of communication, it is worth mentioning as a milestone in the history of radio communications.

World War Two necessitated innovative approaches to communications, and the American company Motorola was the first to develop a handheld portable ‘Walkie Talkie’.

As the Transistor and solid-state electronics were not invented till the 1950s, the wartime Walkie Talkie used ‘Thermionic Valves’ (Tubes in the USA). This meant that they were not particularly efficient, and quite large in size.

The Motorola-designed Walkie Talkie was however an important step forward in radio communications development.

Private commercial use of Two Way Radio by businesses in the UK started just after the war in the late 1940s. This allowed businesses to instantly communicate with their drivers out on the road and was very useful for Taxi firms.

Early equipment was not particularly efficient compared with the latest Digital & Analogue radios available now. Reasons for this include, inefficient use of frequency bands (wide bandwidth), and less efficient electronics available to the designers of the equipment.

In equipment prior roughly to the 1980s, the frequency that the radio was required to operate on (set by what is now OFCOM), was controlled by a ‘Crystal Oscillator’.

These had to be custom made for a particular frequency and then installed into the Two-Way Radio. Once installed, they needed to be set up using a Radio Communications Test Set.

Modern equipment does not require crystals to be purchased and installed but does instead require the radio to be connected to a computer system and programmed to the required frequency and options.

Modern Two Way radio systems are sometimes also integrated into the internet, and it is possible to communicate using a handheld Walkie Talkie, from a field in the UK to a factory in Australia.

To do this the signal is received from the handheld radio by a Digital Repeater Base station located near and within range of the handheld radio. The voice signal is then fed onto the internet by the Repeater.

At the Australian end is another internet-connected Repeater, which then transmits the voice signal out to the nearby Australian factory worker’s handheld Walkie Talkie.

When the Australian worker talks back, the process works in reverse.

For more information on the history of two-way radio, check out other articles on our site.

Author: Craig Miles BSc( Hon’s), PGCE

https://yesway,co.uk

Digital Two Way Radio

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Preventative Maintenance

Preventive maintenance programmes  are the key to reliable, long-life operation of electric motors.
Whilst AC Induction Motors are particularly reliable in service, almost all electrical equipment requires periodic planned inspection and maintenance. Planned preventive maintenance ensures electrical motors, and starters are kept in good working condition at all times. This is critical for businesses that rely on electric motors. A scheduled routine of motor inspection should be carried out throughout the motor’s life. Periodic motor inspection helps prevent serious damage to motors by locating potential problems early.

Periodic Inspections

Planned electric motor maintenance programmes are designed to help prevent breakdowns, rather than having to repair motors after a breakdown. In industrial operations, unscheduled stoppage of production or long repair shutdowns is expensive, and in marine shipping environments, a potential safety issue. Periodic inspections of motors are therefore necessary to ensure best operational reliability.

Preventative maintenance programmes require detailed checks to be effective. All motors onsite (factory, ship etc) should be given their own individual identification (ID) number and have a record log. The record log is usually computerised these days. The motor records kept should identify the motor, brand, inspection dates and descriptions of any repairs previously carried out. By record keeping, the cause of any previous breakdowns can help indicate the cause of any future problems that might occur.

All preventative maintenance programmes should refer to the equipment manufacturer’s technical documentation prior to performing equipment checks.

There are simple routine maintenance checks that can be applied to three phase induction motors, which help ensure a long service life to a motor. 

The Simple checks that can be carried out, include a review of the service history, noise and vibration inspections. Previous noise issues could for example be due to motor single phasing. Previous vibration may have been due to worn bearings, which allow the Stator to turn. Other checks include visual inspections (damage and burning), windings tests (insulation resistance & continuity), brush and commutator maintenance (dc motors) and bearings and lubrication.

Inspection frequency and the degree of inspection detail may vary depending on such factors as the critical nature of the motor, it’s function and the motor’s operating environment. An inspection schedule, therefore, must be flexible and adapted to the needs of each industrial or marine environment.

A modern approach to electric motor preventative maintenance is to connect the motor to the Internet cloud, or local company server network. This can form part of your ongoing business improvement process.

Motor performance parameters such as phase current, rotational speed, heat and vibration, can all be recorded using sensors.

The sensors are attached either directly to the motor, in the case of vibration sensing, or connected to the power supply feed cable.

Wireless technologies such as LoraWAN can be used to connect remote machinery to the Internet of Things Cloud.

This is also known as IOT or IIOT.

(c) Craig Miles 2019.  craigmiles.co.uk & yesway Ltd

For bespoke electrical training for business & individuals with Craig, call Yesway on  +44 (01522) 740818