Long range radio communication

A wide area radio system is a large network of connected sites, each with their own radio infrastructure. As each site receives data it sends an audio transmission to the next site and an onboard computer transmits the audio to each site necessary for broadcast. This all happens in under a second—providing quick and seamless communication across hundreds of miles. 

(highland wireless)

how it works

send data bits long range
Transmit each bit of data with energy. Receiver looks for energy and recovers the data

RF energy received comes in via an antenna

Taller antennas necessary for Lower Frequencies are better 

Sensitive receivers pick up weak signals.

3dB more sensitive is as good as 2X TX power 

10dB more sensitive is like 10X more power

The principle things that affect communication range:

 Transmit power
 Receiver sensitivity

When a receiver’s sensitivity is increased by 10 times, it provides the same communication range improvement as increasing the transmitter power 10 times.

 Antenna gains and antenna heights.

Very tall/long antennas (Low Frequency) are bigger and better. The bigger the antenna, the better the reception. Lower frequencies typically use longer antennas, and are an important factor in why low frequencies receive better signals.

 Frequency of the system

The faster the frequency, the shorter the range. VHF is range than UHF because VHF waves have more power per Every RF engineer knows the equation for RF communication that shows the higher the frequency of the system, the more the loss. 

 The energy per bit (baud rate/data rate)

 Local interference
 In-Band Noise filtering

High performance radio receivers have many filters in them that are high performance. such filters are

- Harmonic filter to eliminate any RF energy/noise that is outside the radio’s band.

-Front End Filter. A good filter to pass signals in the band and reject out of band noise into the receiver. 

- Precision channel filters to filter out any other interference, and even adjacent channels.

Raven