Transmitter power output (TPO) is the actual amount of power (in watts) of RF energy that a transmitter produces at its output. This is not the amount of power that a broadcast station reports as its ERP, such as "we're 100,000 watts of rock 'n' roll", but is in fact many times less for the high-power VHF and UHF stations. The radio antenna's design "magnifies" the signal toward the horizon, creating gain. There is also some loss (negative gain) from the feedline, which reduces some of the TPO to the antenna by both resistance and by radiating a small part of the signal.
The basic equation is: TPO × lossfeedline × gainantenna = ERP
The FCC proposes for unlicensed transmitters operating in the TV bands (Channels 4-51), a transmitterpoweroutput limit of 1 watt in the white channel for fixed facilities and 100 mW for portable facilities.
Those loose ends involve the proper use of a spectrum analyzer as the poweroutput measurement instrument.
So perhaps the topic of DTV signalpower, which is so different from analog TV signalpower, is of interest to many readers.
In radio transmission, transmitterpoweroutput (TPO) is the actual amount of power (in watts) of radio frequency (RF) energy that a transmitter produces at its output.
This is not the amount of power that a radio station reports as its power, as in "we're 100,000 watts of rock 'n' roll", which is usually the effective radiated power (ERP).
There is also some loss (negative gain) from the feedline, which reduces some of the TPO to the antenna by both resistance and by radiating a small part of the signal.
Feeds |
Contact