SGC SG-500 SmartPowerCube™ User’s Manual, Page 9
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PTT – Push-to-talk control. This keys the amplifier circuitry when this line is grounded, and the PTT
control switch is set to manual.
ALC – Automatic Level Control. A positive-going voltage is present on this line for use with
transceivers equipped for ALC input control. See the ALC control description.
BAND 1 – BAND 6 – Bringing the appropriate line low (to ground) selects the desired input filter for
domestic operation when the front-panel FILTER SELECT switch is set to MANUAL. A simple rotary
switch box can be constructed for this purpose. With the FILTER SELECT switch set to AUTO (for
Export use), input filters are selected automatically each time you key the exciter.
FAN – The optional cooling fan (SGC PN #51-82) cable plug inserts into this connector for power and
fan control.
7.0
Amplifier Operation
This section intends to get you on the air using your new amplifier with maximum ease. Before starting,
check the following items.
• Ensure you are using a DC power source capable of providing at least 14 VDC at 40A or greater. Do
not run the amplifier and transceiver from the same supply.
• Check that the power cables are firmly terminated at the power strip on both the amplifier and power
supply. The screws should be firmly tightened so that the cable lug terminals are flat against the strip for
best mechanical and electrical contact.
• Ensure the amplifier, transceiver (and any other station components such as the SG-235, or manual
antenna coupler) are connected to a proper RF grounds.
7.1 Test Transmission
Start by testing into a 50-ohm RF dummy load connected into the RF OUT jack on the SG-500. We
recommend installing a RF power meter in-line to monitor your transmitted output power.
NOTE:
You cannot perform this test with a 40A power supply.
a.
Set the PTT and FILTER select switches on the front panel to AUTO, and turn the power on. The
red LED should light.
b.
Select CW mode on your transceiver, and reduce the power output control to minimum. Note:
other carrier modes (AM or FM) can be used if your transceiver does not have CW capability.
c.
Set the transceiver drive for 25W in CW mode. Turn the amplifier on and switch the radio to
voice, do a test count, and check that the power peaks on the meter. Turn the amplifier off, reset
the transceiver to 35W in CW and repeat voice test. When the voice peaks begin to activate the
attenuator, you have passed the best level. Reduce the drive in 5W increments until the attenuator
does not activate on voice peaks.
d.
Re-adjust the power output control just below the “break-point” (the top of the input range before
the ATTEN circuit activates). You have now found the “sweet spot” at which you can drive the
amplifier to maximum output with minimum drive. This is the recommended drive method to be
used whenever practical.