A passive long-wire antenna installed in the best possible
position with a matching impedance and a shielded lead
cable, is usually sufficient to allow a satisfactory reception
quality.
Alternatively you can install an active antenna. The input
resistance of the amplifier of an active antenna is very high, so
that only a very short whip is necessary. The output resistance of
the amplifier is 50Ω throughout the specified range, so that a
corresponding coaxial cable of also 50Ω is sufficient to carry an
antenna signal without further loss of impedance to the receiver
input. The difficulty in the realisation of a good active antenna is
to make the integrated amplifier and the impedance converter
linear and that it is not over-modulated by strong signals from
nearby transmission stations which cause self generated
interference signals to be passed on to the receiver. As a rule
this is only possible with an efficient amplifier and the
corresponding power consumption, it is a challenge therefore,
for the developer to find the best solution between the highest
linearity and the lowest consumption.
Because of the smaller dimensions, it is easier to find a suitable
position for installation of an active antenna far away enough
from disturbing influences. The lead to the receiver via the
shielded coaxial cable is uncritical. Using a high quality active
antenna will give an optimum reception.
