Power Consumption of MX-P50M Amplifier and FT-817ND

I setup a 12V, 30A power supply I have for another project to use with the MX-P50M Amplifier and the FT-817ND. I adjusted the power supply such that is has an output voltage of 13.8V. Here are the readings on 20m:

Current draw on Receive with amplifier on standby: 0.36A

Current draw on receive with amplifier on: 0.4A

Current draw with 1/2W in / 10W out : 3.69A

Current draw with 1W in / 20W out: 5.4A

Current draw with 2.5W in / 45W out: 7.2A

Current draw with 5.0W in / 60W out: 8.3A

Note that the power was measured with an SWR/wattmeter and at 5W input is clearly exceeding the 45W rating of the amplifier. So with this power supply I would limit to 20W with the magnetic loop antenna so just need to limit output power to 1W on the FT-817ND.

Next tested battery power. My portable power is provided by two 12V 7Ahr gel cell batteries connected in parallel. I hooked this up to my charge controller and measured the output voltage at 12.6V. Here are the consumption measurements:

Current draw on Receive with amplifier on standby: 0.36A

Current draw on receive with amplifier on: 0.39A

Current draw with 5W amplifier off: 1.77A

Current draw with 1W in / 20W out: 5.25

Current draw with 2.5W in / 24W out: 6.38A

Current draw with 5.0W in / 37W out: 7.0A

For 20W current draw remains the same as the power supply by my max power output is limited to 37W.

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6 responses to “Power Consumption of MX-P50M Amplifier and FT-817ND

  1. John Doroson March 7, 2018 at 7:18 pm

    I am replacing the MRF186 in my MX-P50M and need to know what the idle current should be set to which would be the amplifier in transmit mode with out any drive. Hopefully you can help me out.
    Thank you for your time.
    John K2JHU…

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    • rjbono March 7, 2018 at 7:28 pm

      Based on my post above:
      with a 13.8V supply voltage the current draw with amplifier on was .4A and with amplifier off was .36A. This would be an idle current of .04A (40mA).

      When on battery power on 12.6V the current draw with amplifier on was 0.39A and with amp off was 0.36A. The idle current in this case was 0.03A (30mA).

      In both cases the FT-817ND was on receive.

      Hope this helps.

      Like

      • John Doroson March 7, 2018 at 8:42 pm

        I guess what I was looking for was receiver in receiver mode AND the amplifier in transmit mode (by shorting the two pins at the control cable end) This I believe would give the true Idle Current. Thanks again.
        John K2JHU…

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  2. John March 20, 2018 at 6:37 pm

    Well I just finished up replacing the DEVICE and I set the idle current to 75ma base on other information I had. I do have a question regarding your amp output at various power inputs. My outputs and current draw from 5 watts to .5 watts are: 80/9.7 – 50/7.8 – 30/6.0 – 10/3.9. Not too far off from yours. I have not found any one else that got more that 45 watts out with 5 watts in. Now my device may have more gain that every one else. So do you run yours at 60 output. I am wondering what would happen if I ran mine at the 80 watt level. Just wondering.
    John K2JHU…

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    • rjbono March 21, 2018 at 1:22 am

      Most I’ve gotten from this is 60w with a 5w drive on 20m. I seem to recall that the max out was lower on higher bands for the same drive. I usually run it at a 2.5w drive when I am portable to save battery.

      Like

  3. John March 21, 2018 at 10:42 am

    Thanks. I did make a mistake. the 80 watts should have been 70 watts. My setup has an automatic switch over to a storage battery whenever we power is lost and I tested the power out with the battery which provided a maximum of 50 watts on 20 meters. So that is how I will run the amp here in the shack. John K2JHU…

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