I-3
Operating Safeguards
It is a known fact that our broadcast transmitters and translators enjoy 50-ohm load impedances.
So much so, that it is imperative you maintain 50-ohm impedances throughout your system. In
return, your equipment will provide you with maximum power transfer to the antenna and
decreased reflected power heading back towards the amplifier pallets, reducing the amount of
magic smoke that gets let out of the power amplifier. Before anything is turned on, ensure that
there is a 50-ohm path from the output of each stage to the input of the next, all the way to the
antenna.
In addition to maintaining proper 50-ohm impedances throughout the signal chain, it is also
important, whenever possible, to make sure the RF drive going to the input of the power amplifier
is removed before turning on or turning off the DC power supply. This is because all of the RF
transistors used in the individual amplifier pallets are fabricated with LDMOS (Laterally Diffused
Metal Oxide Semiconductor) technology. Nice and linear yes, but they do not like to make any RF
power when their supply voltages are not within a specific range. When you first turn your power
amplifier on or off, the DC power supply’s output voltage may take a while to stable out to a safe
operating voltage. Ten seconds wait before applying the RF drive will ensure no issues arise.
Our power amplifiers are designed to reliably generate a specific RF output power. Failing to
adhere to overdriven amplifier warnings can decrease the reliability of your system, and frankly,
makes our repair department busy and grumpy. If you need to transmit to a little larger coverage,
you are better off increasing antenna gain, and more importantly, antenna height above average
terrain. On TV and FM broadcast frequencies, insufficient antenna height puts an upper limit on
your range, regardless of power levels, as the
distance from your antenna to the radio horizon is
limited.
