Q.        What do you mean by two-way radio?
A.   A two-way radio is a radio that transmits and receives radio signals. A walkie talkie is what most people who aren't in the industry would call .

Q.       How far will a radio talk?
A.    Well, that all depends. One portable (hand held) radio trying to speak directly to another will probably talk about 1 kilometre depending on terrain and weather. A mobile can talk 2 to 7 kilometres depending on the same variables. A system including a repeater can probably talk 5 to 15 kilometres A trunked system can talk much further

Q.   What is a repeater?
A.   repeater is a device that takes a radio signal (for example from your portable radio) and re-transmits it at higher power for extended coverage.

Q.   What is the advantage of two way radios over mobile phones
A.    Instantaneous communications. For safety, security, efficiency and financial reasons, two-way radio is the single, most widely used communications solutions. There is no dependency to any provider is the main advantage provider and user is a single agency like Police.

Q.   How do two way Radios communicate with each other?
A.   The two most common ways that two way radios communicate are:-
In SIMPLEX: - This means that you talk radio to radio. The radio signal travels out of the antenna of the transmitting two way radio into the air, and if another two way radio is in proximity and on the same channel that the transmitting two way radio is on, then it will receive the incoming transmission.
OR
Via a REPEATER: - This means that the radio signal travels out of the antenna of the transmitting two way radio into the air, which is picked up by a signal booster (the repeater) which re-transmits the original signal to the receiving radios. Repeaters are used to boost the strength of a radio signal either inside a building where the signal needs to penetrate many layers or outside to extend the range of the two way radio. A repeater can only boost one channel, so you need an individual repeater per channel you want boosted.
All two way radios communicate within FREQUENCY BANDS; these frequencies are divided into various bandwidths (for radio) some of which are: -

• HF - 3-30 MHz (27 MHz-CB, between 26.965Mhz and  27.05 MHz)

• VHF – 30 - 300 MHz, 49.25 to 174 MHz  (VHF H/B-136-174MHz)

• UHF - 300- 3000 MHz.(uhf403-470,uhf2, 450-529 MHz (CB channels 1 – 40 are between 476.425 and 477.460 MHz)
• 800 MHz Digital and Analogue Radios - Usually in the 800 MHz range either between 820 to 825 MHz or between 865 to 870 MHz.

  Table of ITU Radio Bands
  Band Number	Symbols	Frequency Range	Wavelength Range	Typical sources
  1	ELF	3 to 30 Hz	10 to 10,000 m	deeply-submerged submarine communication
  2	SLF	30 to 300 Hz	100 to 1000 m	submarine communication, ac power grids
  3	ULF	300 to 3 kHz	1 to 10 km	earth quakes, earth mode communication
  4	VLF	3 to 30 kHz	10 to 100 km	near-surface submarine communication,
  5	LF	30 to 300 kHz	1 to 10 km	AM broadcasting, aircraft beacons
  6	MF	300 to 3000 kHz	100 to 1000 m	AM broadcasting,
  7	HF	3 to 30 MHz	10 to 100 m	Skywave long range radio communication
  8	VHF	30 to 300 MHz	1 to 10 m	FM radio broadcast, television broadcast, DVB-T, MRI
  9	UHF	300 to 3000 MHz	10 to 100 cm	microwave oven, television broadcast, GPS, mobile phone communication (GSM, UMTS, 3G, HSDPA), cordless phones (DECT), WLAN (Wi-Fi), Bluetooth
  10	SHF	3 to 30 GHz	1 to 10 cm	DBS satellite television broadcasting, WLAN    (Wi-Fi), WiMAX, radars
  11	EHF	30 to 300 GHz	1 to 10 mm	directed-energy weapon (Active Denial System), Security screening (Millimeter wave scanner), intersatellite links, WiMAX, high resolution radar

Q   What is Line Of Sight ?   

A clear LOS exists when no physical objects obstruct an imaginary straight line drawn     connecting the antennas on either side of the link.