SGC Smartuner SG-211, Operating Manual

Page: 38 / 50

SG-211 User’s Manual
© 2004 SGC Inc. Page 36
With normal use, the internal batteries have a service life
that approaches the shelf life of the batteries themselves.
Battery replacement will be required at intervals of five
years or more. The very low average current drain is
achieved by using low power latching relays that draw
power only during the matching process. A very low
power standby mode for the sensors and the
microprocessor limits standby current to a few
microamperes.
4.2 The Matching Network
The matching network consists of a four-to-one step down
transformer that also performs an unbalanced to balanced
matching function. The output of the transformer T1,
at12.5 ohms, serves as the input to an adjustable L
network. Shunt inductor L1 across the transformer output
steps down the effective impedance, especially at lower
frequencies. The L network transforms the impedance up
to match the complex impedance of the antenna. This is a
well established matching concept in military manpack
applications spanning many years.