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Solutions
There are certainly other ways than those listed above to kill
amplifiers and power supplies. Lightning damage is the most notable omission from this
article. However I think most of the above problems are often overlooked in many
installations.
Increase Transmitter hang time
A simple reduction in thermal shock and rapid current change problems can be made by
increasing transmitter hang time to reduce the number of turn on/off cycles. A small
increase in time -out can significantly reduce the number of cycles the system must endure
each day. Very often this is programmable from a paging terminal or the transmitter
itself.
Turn on fans and other cooling equipment immediately upon turn-on.
In RF amplifiers, look for designs that have control circuitry that turns on the
fan(s) immediately upon RF signal application rather than waiting for the heat sink to
reach a predetermined temperature. This effectively increases the thermal time constant
and reduces dT/dt.
Be aware of drive power overshoot and design the system with
the highest input amplifier possible.
Turning down an exciter to less than 50% of it's rating to match the
amplifier's input power rating may be inviting drive overshoot problems. Look closely at
the exciter's power control circuitry and measure the overshoot if possible. Running the
exciter at a higher drive power and adding additional attenuation at the input to match
the amplifier's rating will reduce this problem.
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