About Those GMRS / FRS Walkie-Talkie
True Effective Communication Range

If you buy a pair of GMRS/FRS walkie-talkies, don't complain about the lack of communication range. The talking range is all determined by certain factors. GMRS/FRS walkie-talkies operate on UHF frequency around 462 or 467 MHz, and UHF frequency transmitting range is limited to the line of sight due to it's short wavelength. Height of the transmitting antenna of the walkie-talkie, and receiving antenna that is free from obstruction increases the range of the GMRS/FRS walkie-talkies:

The GMRS/FRS walkie-talkie effective range will increase:

  (1) If you are on top of the highest hill or mountain with an unobstructed view of the distant area of the location of your communicating partner..

  (2) If you're upon the upper floors of a tall building near the window, or on the balcony with an unobstructed view of the distant area of the location of your communicating partner.

  (3) If you have high height above the ground to the point that you can see over the horizon.

 

The GMRS/FRS walkie-talkie effective range will decrease:

  (1) If you are inside of a building or a house made of solid metal, or concrete, or masonry or rocky structure.

  (2) If you're deep down in a valley.

  (3) If you're in a tunnel, or in a basement, or under a bridge or a overpass, or underground.

  (4) If you have a hill or a mountain sitting between you and your communicating partner.

  (5) If you have thick woods between you and your communicating partner.

  (6) If you have low height above the ground to the point that you can not see over the horizon.

Even cell phones looses it's service when it's under those factors above, and cell phones operate on the UHF frequency.

The higher you are, and free from obstruction, the longer your communication range.

To calculate the line of sight communication range, and height of your GMRS / FRS walkie-talkie's transmitting antenna by using these formulas:

D = distance in miles
H = height above the ground in feet.


D = Square root (2H)
OR
D = Square root (2 x H)


H = D^2 / 2


OR

In the Metric System

D = distance in kilometers
H = height above the ground in meters


D = Square root (17H)
OR
D = Square root (17 x H)


H = D^2 / 17

 

To calculate the line of sight communication range, and height of the transmitter antenna, and the receiving antenna of the walkie-talkies by using these formulas:

 

    D = distance in miles
H
TX = height of transmitting antenna above the ground in feet.
H
RX = height of receiving antenna above the ground in feet


D = Square root (2H
TX) + Square root (2HRX)
OR
D = Square root (2 x H
TX) + Square root (2 x HRX)

 

OR

In the Metric System

    D = distance in kilometers
H
TX = height of transmitting antenna above the ground in meters.
H
RX = height of receiving antenna above the ground in meters


D = Square root (17H
TX) + Square root (17HRX)
OR
D = Square root (17 x H
TX) + Square root (17 x HRX)

For Example:

  So if you stand 6 foot tall, and and your walkie-talkie is 5 feet 6 inches above the ground, and your communication partner stands 5 foot 6 inches tall,  and his or her walkie-talkies is 5 feet above the ground, and both of you are on flat terrain, and free from obstructions, your talking range would be 6.47 miles with those GMRS / FRS walkie-talkies in the line of site communication range.

6.47 miles = square root (2 x 5.5 feet) + square root (2 x 5 feet)

  If you are standing on your balcony at you high rise apartment at 28 floors above the ground or 336 feet above the ground with your GMRS /FRS walkie-talkie, your line of sight talking range would be 25.9 miles.

25.9 miles = square root (2 x 336 feet)

                !Warning!
Make sure you have a FCC license before you transmit on Channel 1 to 7 with an effective radiated power over 0.5 watt, and Channel 15 to 22 at any legal transmitting power level, and use channel 20 (462.675 MHz) for only emergency communication, or else you could risk up getting fined up to $10,000 fine by the FCC for illegally operating of a transmitter, or you could do some prison time, or both depending on the seriousness of the offense.

 


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