Fiber-Span LLC FS31H-4 User Manual

 

 

UHF Headend Repeater Unit 

 

 

User Manual Ver. A 

Document ID: FS31H-4X -USR 

            Page 8 of 32 

 

When multiple RF carriers are input to an RF amplifier, the RF output power will be the input 
power plus the gain. 

Power output = Power input + Gain (in decibels) 

Power output = Power input x Gain (in Watts) 

As seen by the preceding figure, the output power tracks the input power linearly.  Eventually as 
the input power increases, the amplifier output power reaches the output power limit.  When this 
happens, intermodulation products are generated at the amplifier output.  The intermodulation 
products with the most likelihood of generation are 2

nd

 and 3

rd

 order.  For every 1dB increase in 

input RF power, the 3

rd

 order intermodulation products increase 3dB.  If one were to plot the 3

rd

order output power on a graph as in the preceding figure, the slope of the 3

rd

 order products 

would intersect the line of the output power plotted vs. the input power.  This point is defined as 
the 3

rd

 order intercept and is used by amplifier manufacturers to characterize the maximum 

output power of an RF amplifier. 

The RF output power of the amplifiers is defined as the total RF output power inside the 
bandwidth of the duplexers.  This RF output power is divided into the number of dominant RF 
carriers at the output of the amplifier.   

The HRU has several purposes.  

x  As a single unit to provide coverage for a single band of wireless service; 

x  As multiple units amplifying coverage for multiple services; 

x  As an amplifier to feed fiber-optic transceivers and provide RF wireless coverage using 

coaxial cable fed from the HRU. 

The following diagrams help illustrate a typical coverage solution for a single band of wireless 
service.

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