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VHF Radio Communication
VHF/UHF Radios are wireless radios usually having frequency
range between 100
MHz to 1000 MHz. They are generally divided into two
categories
a)
Mobile (runs on 12V Car Battery).
b)
Handheld portable Radios.
Yes, generally licenses are required for using them. The
licensing
authority allots spot frequency (MHz) for their
operation. In India, Wireless
Planning Commission (WPC), NEW Delhi allots frequency
licenses for one year
with provisional for renewal. The license calls for annual
license fee and royalty
The Radio manufacturers give a custom built window based
Radio Service
Software (RSS) from which the Radios can be programmed. A
PC is required for
programming the Radio.
The software file generated on programming of a Radio is
called code plug.
A VHF Radio can be programmed in a Hundred ways. Code plug
programming is
much more than frequency programming.
It requires careful analysis of the user working style and needs, before
programming the radio. Mere tuning the frequency in all the
radios, will
lead to fish market type of noisy and unwanted
communication making the users unhappy.
a) PL/DPL coding - When there is a single frequency and multiple groups
are required to be made, this feature is used for making water tight groups.
b) SCAN Mode - When there are more than one group of subscribers and they
need to be in more than one group at a time, then scan options is enabled
for scanning all the groups.
c) Battery health indicator - For handheld radios, one of their buttons can
be programmed for indicating the status of battery health (Full charge,
50%, 10% etc.) over a multi colour LED.
Handheld Radios are available with two types of programming options.
a) Keypad Programming
b) Computer Programming.
Keypad programmable radios does not need PC for programming. They can be
programmed by pressing the keypad buttons. However, they suffer the
disadvantage of limited programming options. Also the program may sometimes
get changed by accidental press of buttons making the radio unusable.
Also, the code plug can not be saved for future maintenance and use.
PC based programming requires the radio to be connected with a PC. The program has got a lot of options and once programmed, the program can be saved in a floppy for future reference. The programming is impossible to get corrupt during field use.
Some typical applications:
a) Cranes & electric cars - Use VHF mobile with DC 12V Linear power supply. Do NOT use SMPS in moving cars as vibration tends to fail SMPC power supply.
b) Diesel Locomotives - Use with DC-DC converter power supply. (Typical Input - 30V to 80V, Output - 12V, 10A)
Ground plane omni directional unity gain Antenna gives the best
price/performance ratio.
Though telephone patch may be an option, but it has got serious
limitations. To have more flexibility with telephone like features, use
Radio Trunking for mobile-mobile, mobile-landline and landline to mobile
connections.
One channel Radio Trunking system consist of a Radio controller with PSTN
connectivity and a Repeater. The subscriber Radios are fitted with a add on
logic card. The Radio trunking controller is programmed for subscriber
radios. The subscriber Radio is also programmed for unique ID.
Select a Radio with a programmable accessory port. The pins of the port can be programmed with the RSS. Make a Radio master and another slave. Program a particular pin on the master radio, such that its High to Low output will trigger change another pin on slave radio. This type of programming can trigger a relay on a slave radio, when some event happens in the master radio located far away from slave radio.
| Sl No. | Item | Manufacturer |
| 1 | VHF Radios, Motorola GM300/950 and GP328/338 | www.motorola.com |
| 2 | Radio Trunking System | www.Smartunk.com |
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