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Thread: IC-730 doesn't increase RF power

  1. #1

    Question IC-730 doesn't increase RF power

    I have an old IC-730 and I'm loving it. The reception is great and I'm making some great contacts on digital modes. I noticed one odd thing, however. I'm transmitting on the lowest power setting (10 watts according to the manual), but when I do increase the power, the meter doesn't rise at all. I wasn't sure if the meter was working correctly, or if I was having SWR issues, so I installed a power/SWR meter between the radio and the antenna, but the new meter only confirmed my results. Its transmitting at exactly 10 watts, and increasing the power using the RF power knob doesn't seem to change anything. Additionally, my power consumption at the power supply is 7 amps at 13.8VDC (less than 1 amp in RX mode). At 10 watts during TX its using 96 watts. Not sure if that is normal or not.

    Any idea how to troubleshoot this? I have the service manual and I'm not afraid to take the radio apart and check values on a multimeter.

  2. #2

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    10w is the minimum power at the lowest setting, a level which is controlled by a seperate resistor on the board rather than the extreme of the potentiometer. If the RF power potentiometer makes absolutely no change to the output power, i would guess the pot has went bad or the jumper connecting it to the board has become disconnected.

    Also, at 10w output, the radio should not be consuming 7Ax13.8V=96watts... Does the radio get warm? Is the fan kicking in at 10w output? How are you feeding the digital audio into the radio (presumably via mic jack connected to a PC sound card output, hopefully impedance and level matched) and what mode is the radio set to?
    Last edited by brandon lind; Thu 20th Aug 2020 at 15:52.

  3. #3

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    It appears to be an issue where the radio is cutting power because the SWR is too high. On a dummy load, the radio transmits full power. The internal and external SWR meters show that i never gets above 1.3:1, but the manual says it can safely go to 2:1. I have been able to calibrate the SWR meter on the radio, but I haven't found a setting to calibrate when the output transistors throttle.

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