By Ong Guan Lin @ Pikachu.


In any organized events, communication plays a pivotal role in contributing to the success of the activity. Similarly in Rainforest Challenge, an event of such magnitude, employment of wireless communication is literally inevitable.

Two-way radio is an apparatus that is capable to transmit and receive (thus the word – transceiver), unlike a broadcast receiver which only receives. Wireless operation permit services, such as long range communications, that are otherwise impossible or impractical to implement with the use of wires. These apparatus appear in walkie-talkies or on-board mobile units. Depending on the mobility and usage, there are many out there to choose from.

Radios communicate with each other through the use of radio waves with varying frequencies. It requires two radios to be of the same frequency to enable contact. Frequency is denominated in Hertz, abbreviated as Hz. (eg. 15 kHz= 15,000Hz or 149.200MHz= 149,200 kHz= 149,200,000Hz)

VHF equipment operates between frequencies of 30 MHz and 300 MHz. FM radios, two-way radios, and television broadcasts operate in this range too.

From past RFCs, use of radios operating at VHF band (non-fixed channel, simplex operation, variable frequencies and user programmable) is widely used and is preferred over radios operating at UHF band. This is because amongst others but not limited to, the robustness of equipment, ease of setting up, the range, and the terrain RFC offers – often densely wooded, hilly territories and differing elevation.

In general, wireless transmission functions at optimum performance in outdoor where there is direct line of sight in addition to a precisely-tuned antenna, effective radiated power of a transmitter, well- positioned set up, weather, terrain and content of mineral in its path.

One frequently asked question would be “With my mobile VHF set, how far I can transmit?” To answer accurately, more transmitting conditions are needed in order to give a clear picture. This is dependent on numerous factors like transmitter output power (expressed in Watt), the gain of antenna (dB), altitude, environmental condition, recipient set up and others.

For your reference, one can send and receiving station located 50 km away can legibly copy your message with a mere 10W transmission when all conditions are near perfect.

CB radio on other hand, while it is popular in USA and Canada, it is hardly used in RFC. It is a low power, short range service in the VHF 150 MHz Citizens Band radio spectrum.

One of many experiences as communication officer in RFC.

In 2010, we erected a twin-stack 6.5 decibel gain base station antenna atop a 30-feet mast (combination of bamboo + extendable/retractable pole), at beach campsite along the shores of Tanjung Leman, Johor. The said antenna was hooked up to a mobile VHF transmitter working at full legal power and gradually decreased as RFC participants moves closer to base camp. The purpose was to monitor and provide support to RFC participants while transversing the feared Twilight Zone.

At the height of a recovery episode, we provided unparalleled and seamless communications in the rescue and evacuation efforts of injured for further medical attention. This encompasses communication with the 7th Brigade Signals Corps of the Malaysian Armed Forces, Royal Malaysian Police Johor for all the 7 districts, our RFC officials in the TZ, RFC event doctor, paramedics, Fire & Rescue Brigade and medical team at Kota Tinggi Hospital.

It was the longest night but one which ended well due to the almost clockwork coordination by the authorities and our RFC officials at our beach campsite.

Some Golden Rules of Radio conversation:

  • Clarity – Your message should be clear enough. Speak slower than normal speed so that people can understand you better, do not shout.
  • Simplicity – Your message should be simple for everyone to understand.
  • Brevity – Your message should be precise and to the point.
  • Security – Do not transmit confidential/sensitive information on the radio.

Some commonly used codes:

  • Affirmative — Yes
  • Negative — No
  • Roger — Information received/understood.
  • Copy — I understand what you just said (after receiving information).
  • Over — I have finished talking and I am listening for your reply.  Short for “Over to you” or it is like passing the mike to you now.
  • Out — I have finished talking to you and do not expect a reply.
  • Clear — I have finished talking to you and will be shutting my radio off.
  • Break — Signals a pause during a long transmission to open the channel for other transmissions, especially for allowing any potential emergency traffic to get through
    • Break-Break — Signals to all listeners on the frequency, the message to follow is priority.

Do you know why in wireless communication, the word “copy” is often heard?

Answer: This does not imply making duplicate. It is actually when a sender transmits a message, the recipient on other end will listen and copy that message (presumably on a piece of paper) and thus the derived word “copy”.

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