User Manual

MT-4E VHF & UHF Receiver & Transmitter Instruction Manual

IM08-MT-4E-TXRX Project 1106

Hardware Tuning and Troubleshooting

If the transmitter front panel NORMAL/OFF/ KEY TX switch is set from the OFF position to the

NORMAL position and the two front panel LEDs both turn ON for less than 2 seconds and then turn

OFF and the RF output power control is set at its maximum in the Power Levels area of the Service

section on the RSS, but the RF output power is considerably less than 8 W and 4 W @ 800 MHz:

check that the synthesizer Reference Oscillator is set to internal reference in the System Setup;

Jumper Settings area of the Service section on the RSS.

check that the output of the synthesizer module on the RF cable as shown on the MT-4E Transmitter

Bottom Component View is 0 dBm (± 2 dBm) and that the RF frequency will change with programmed

channel changes in the RSS. If this is not the case, it is most likely that the synthesizer or the UDB or

both are faulty. The fault may be associated with the synthesizer code, the DSP Code or both.

Transmitter Amplier

Set the front panel switch on the transmitter to KEY TX and check that the Transmitter Output Power

is set appropriately. The output power can be adjusted in the Power Levels area of the

Service section on the RSS.

Check the following pins on connector J1 (while the transmitter is keyed):

Pin Signal Monitored Typical voltage

1 RF Enable / Power Control (+0.5 to +3.0 VDC

corresponds to 0.5 to 8.0 W RF Power Output)

+0.5 to +3.0 VDC

2 Regulated +9.5 VDC from motherboard +9.5 VDC ± 5 %

3 Voltage from motherboard +13.8 VDC line +10 to +17 VDC

Pins are shown on the MT-4E Transmitter Bottom Component View.

If Pin 1 is not within tolerance, the most likely fault is in the UDB or Synthesizer module. If Pins 1, 2

and 3 are within the specied tolerances, and there is no RF output power, the most likely fault is in

the Amplier.

To test the RF power amplier sub-assembly, set the output power to maximum, using the Power Level

Adjustments in the Service mode of the RSS software and drive the input of the amplier with a 0 dBm

RF signal. Check that the RF power output is 8.0 W and 4.0 W @ 800 MHz when the front panel switch

is set to KEY TX.