Alternatively an active antenna can be used. The input resistor in the
amplifier of an active antenna is very high, therefore it requires a very
short whip. The output resistor of the amplifier is 50: throughout the
whole of the specified frequency range, so that a corresponding coaxial
cable also with 50: which transmits the signal from the antenna without
further loss of adaptation. The difficulty in the realisation of a good active
antenna is that the integrated amplifier and the impedance transformer
are as linear as possible and not overmodulated by strong signals from
nearby transmitting stations creating self generated interference to the
receiver. This is normally only possible with powerful amplifiers with
equally high voltage use demands finding a good solution between
highest possible linearity and the least amount of draw of current.
Because of the small dimensions, it is easier to find a place for
mounting an active antenna away from disturbing influences. The lead
to the receiver through the shielded coaxial cable is uncritical. The use
of a high quality active antenna will give an optimum reception.
