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Flex 6400M not putting out 100 watts

I have a nice Flex 6400M that is being powered by an Astron 50M. The power supply is set to put out 14.2 volts, and this voltage only drops .5 volts when I key up the radio. On the amp. meter I am seeing 23 or 24 amps of draw. The radio is only putting out 93 watts on 40 meters and only 95 watts on 75 meters. What do I need to do to get this radio at 100 watts of slightly more?


  • Neil D Friedman N3DF
    Neil D Friedman N3DF Member ✭✭✭
    edited July 2022

    How are you measuring output?

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    Use a program such as FRStack to check PA voltage inside the radio when setting TUNE to 100. Then you can see voltage drop through power cable, any external fuses, Power Pole connections, then internal fuse. I run my switching supply at 14.5 volts at back of supply on TX and have no problem making 100 watts although I run it a LOT less wattage to drive the PG XL.

    Also difference in signal from 93 to 100 watts out will not be detectable over the air.

    Dave wo2x

  • Ha Gei
    Ha Gei Member ✭✭✭
    edited July 2022

    Just ignore that. This is neglectable difference and can already by that the radio sets back on a not perfect SWR. As David already wrote .. NO ONE can see that difference over air. You need to go down to 50W to make noticable difference , but just on constant carrier..in SSB or CW the next noticable step might be 6db ( 25W) down

  • Steve Ellington
    Steve Ellington Member ✭✭

    You won't find the answer here. Most will respond with "ignore it", it doesn't matter, no one can hear the difference, you have voltage drop, etc. This has been going on since the first 6000 series and these are not usually the answer or at least not the answer we want to hear. After all, if the specs say 100w then it should do so.

    Now we do know that software revision can affect output power as it did in the recent update on version 3. 160 meter power was low and the update brought it up to over 100w. Others have sent their rigs in to Flex for "calibration" with positive results. I have no idea what is going on with this.

    I would suggest using FRstack first to endure proper voltage to the insides then opening a help desk ticket with Flex if none of the above help.

  • WX7Y
    WX7Y Member ✭✭✭
    edited July 2022

    So with .5 volts voltage drop the radio is seeing 13.7 volts, is this measured with a volt/ohm meter at the Radio's Power Pole connectors, Keyed Down and 100% power which as Dave mentioned is a bit low?

    There is another cause of voltage loss inside the radio, there is a automotive type Fuse that can have oxidation on the contacts and fuse legs that you can clean and replace every few years A tiny bit of Electrical Antioxidant will help keep them clean and conducting.

    You can measure both voltages as Dave WO2X said with FRStack, K9DUR has a nice LITTLE program called SDRMonitor (https://k9dur.us/smartsdr_utilities.php) that gives you the voltage input and radio TEMP with out all the overhead of FRStack if you aren't using it for something else but SDRMonitor doesn't tell you if the fuse voltage drop is excessive at the PA Board which is the most important voltage for low Power Output power issues.

    Dave also has a great NODE-RED flow to monitor the voltages, Temperature and Fan RPM in the 6400 and 6600 radios and all but the Fan speed in the 6300, 6500, and 6700 radios.

    Using Node-Red FlexRadio flow my OLD 6700 with cleaned internal fuse measures 14.04 Volts input @ Power Poles and 13.85 at the PA FUSE in RX mode and 12.43A @ 95 Watts output on 40 meters, If I raise the Power supply voltage a slightly higher then 100 Watts is easily possible.

    So in a Nut shell raise your power supply voltage up .3 to .5 Volt and see what things look like

  • Dan Trainor
    Dan Trainor Member ✭✭✭

    Also SmartSDR for MacOS monitors DC Voltage and Temp and displays on the screen. Look at the upper right of screen within the title bar.

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