TN490 19” Rack Mount High Power Amplifi ers
MT-3/4 Radio Systems
TECHNICAL NOTES
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TN490, REV 2-0-0, © Aug 2016
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Power Amplifi er Operation
The 19” rack mount high power amplifer has a heavy duty heatsink and an RF switched cooling fan. The power
amplifi er has four standard LEDs (not available on the VHF rear panel mount), and a summary alarm pin.
The LEDs operate as follows:
Label Color Description
DC ON Green Activates when DC power is connected.
LOW OUTPUT Red Activates when the output power drops to 80-85% of output power.
HIGH VSWR Red Activates when VSWR exceeds 2.5:1.
HIGH TEMP Red Activates when the amplifi er exceeds safe operating temperature.
The three pins on the rear of the amplifi er operate as follows:
Pin Description
ALARM A summary alarm that activates (< 1 Vdc) when any of three alarm conditions activate
(Low Output, High VSWR or High Temp).
CTRL When this pin is pulled to ground, the output power is reduced by 1 to 1.5 dB.
SH/D When this pin is pulled to ground through a 0 to 50 K Ohm resistor,
the output power is reduced by up to 4 dB.
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