SG-2000 MANUAL
37
The SGC Building, 13737 S.E. 26th St. Bellevue, WA. 98005 USA
©1995, SGC, Inc.
TEL: (206) 746-6310 FAX: (206) 746-6384
power is drawn, and nothing may work correctly because the voltage will drop
dramatically.
Let's consider wire sizes between the power source and the radio. At 25 feet we
recommend number 6 wire. At 12 feet we also recommend number 6. At 2 feet we
recommend number 8, but we use number 6 because its more in line with our practice
of building generous margins into all SGC products.
10.2
AC Power Supplies
There are two ways to convert high voltages AC from either 110 or 220 Volts to DC
voltages suitable for operation of an HF radio, generally 12 Volts DC: 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 of inferior design are not as capable
of continuous duty operation.
Some switching power supplies are quite good. Unfortunately, they are also very
expensive and not as cost effective as a transformer-rectifier type power supply.
10.3
Transformer-Rectifier Supplies
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 from the 400 Hz AC power source.
High peak current is an important consideration if you are planning to operate in the
voice mode. But if you are planning to operate in the data mode or will be using the
transmitter on a more continuous basis, output capacity is less a factor than how
heavily-built the transformer in the power supply is.
SGC does not generally recommend switching type power supplies in either a mobile or
a base station installation for these two reasons: first, switching power supplies easily
generate noise from the switching circuitry; second, under heavy loads, the switching
type power supplies tend to stall and cause an interruption of power to your radio.