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The SGC Building, 13737 S.E. 26th St. Bellevue, Washington 98005 USA
P.O. Box 3526, 98009 Tel: (425) 746-6310 Fax: (425) 746-6384
© 1997 SGC Inc.
There are two ways to convert 110 or 220 volts AC to 12 Volts DC, the most common DC input voltage for
transceivers. The typical methods are via conventional transformer-rectifier power supplies and switching-type
power supplies.
SGC does not recommend switching-type power supplies for continuous commercial
service for two reasons: First, unless the switching power supply is of exceptional design
and properly installed, it will generate RF "hash," which will create a high local noise level.
Second, switching-type power supplies tend to fail when used in continuous-duty operation.
Some switching power supplies are quite good. Unfortunately, they are also very expensive and are not as cost
effective as transformer-rectifier type power supplies.
Many transformer-rectifier power supplies are of the regulated type. This means that
they will hold an output voltage constant over a wide range of input voltage and output load
conditions. If regulated power supplies are not well designed, they can also create RF
"hash." This interference will create a buzz when the equipment is receiving; if the problem
is severe, a bit of this distortion could also be present in the audio when transmitting. For
this reason, SGC recommends the PS-50 regulated power supply if high current demands
(such as those encountered in operation of a transceiver) are expected.
Transformer-rectifier power supplies are by far the most reliable available. They are able to operate over a wide
range of input voltages and offer resistance to failure under periodic overload conditions, which would cause a
switching-type supply to fail.
Supply voltages for such power supplies are generally 110 and 220 volts AC with a frequency of either 50 or
60 Hz. Many aircraft also have 400 Hz AC available from their engine driven alternators, but in these instances, it is
usually better to power equipment from 24 volts (generally available on aircraft) than install a power supply to
operate equipment off the 400 Hz AC power source.
Another consideration in selecting a power supply is how much capacitance is provided
in the output of the power supply. This is important because capacitors in the output of the
power supply store electricity. Acting like batteries in this case, capacitors provide
instantaneous high peak output current.
A Regulated power
supply will hold an
output voltage constant
over a wide range of
input voltage and output
load conditions.
TRANSFORMER-RECTIFIER SUPPLIES
High Capacitance
power supplies
provide
instantaneous high
peak output current.
AC (MAINS) POWER SUPPLIES
We recommend
Transformer-Rectifier
power supplies.
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