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ALC 6400

Mike-N1VE Member ✭✭

When transmitting with the 6400, using the Maestro, I am not getting any ALC meter reading. I have looked through a couple Flex PDF manuals, but I haven't found anything of substance about the meter or controlling the ALC. Can someone direct me to the proper information?



  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Mike, Are you talking about Phone or CW operation? If Phone, then you don't use ALC to set drive, you would use the Mic level meter. The goal is to keep the peak level somewhere between -5 and -10 dB, such that it never goes into the red (i.e. never above 0 dB).

    If you are referencing the ALC meter in CW, Here is what the SmartSDR manual says:

    41.7.2 CW Transmit Control Panel

    ALC bar meter: This meter is an indication of the analog ALC hardware input levels provided by external power amplifiers. If there is ALC being displayed, the external power amplifier is notifying the exciter (FLEX-6000) to reduce the drive level.

    NOTE: When operating on Phone mode, if hardware ALC is indicated, the default RF Power and SWR meters will be momentarily hidden and the ALC meter displayed indicating a positive ALC condition exists.

    Let me know if this did not answer your question.

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

    If you are not using an amp that provides ALC feedback to the radio then you will not see ALC indication.

    As Len indicated, set TX audio peak level for SSB to not exceed -5. It should never go into the red. Set power out to level to give desired output drive level for amp.

    Dave wo2x

  • Mike-N1VE
    Mike-N1VE Member ✭✭

    Thank you for your responses to my question. My amplifier does not use ALC, but since my other radios show ALC, I wondered why the Flex doesn't.

    I am using SSB and a Maestro.

    I will check my mic level meter. And I will print your responses and add them to my Flex info. folder.


    Mike, N1VE

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Glad we could help Mike. These Flex radios have really good, clean audio as long as you don't exceed the recommended mic level setting.

  • Daniel Drolc
    Daniel Drolc Member ✭✭

    I have flex 6400 and als-600 amp, My alc line was connected between rig and amp with old 3.1.12 version with out any problem , but now upgrade to 3.2.31, now I need to disconnect alc line because once a wile no output on flex 6400,

    Hope new version will cored this problem


    Dan VE2ZC

  • W4AFK Bruno
    W4AFK Bruno Member ✭✭

    Len KD0RC - Are you saying that I can have an ALC line between the Expert 1.3K FA and the FLEX-6400 for voice mode? My TS-480SAT is also connected to the 1.3K FA amp (input 2) and it has the ALC line hooked-up. No problems whatsoever, rock stable, no tripping or overdriving.

    With the FLEX is crazy as there is no ALC link to the amp. Setting the amp and radio for different bands, etc. is a pain, and the amp will at times trip as it's over driven depending on the band and antenna. Again, this is NOT an issue with the TS-480SAT using the same amp and same antennas (the SPE's tuner handles any VSWR mismatch for both radios). So if you are saying that we CAN have the amp ALC control the radio, then I will definitely get it done.

    If this is the case, what's needed? I read that the USB control cable that's sold for the amp has no ALC line because "the FLEX has no analog ALC".

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Bruno, there is indeed and ALC jack on the back of a Flex 6400. I have an Elecraft KPA 500 amp, so I don't use it. Since I have never used the ALC line, I can't give direct advice on its use. I would say read the documentation very carefully (Flex and SPE) then proceed accordingly. Maybe some experiments into a dummy load will set you on the right path.

    Does the amp have an ALC line? The fact that the USB control cable does not contain ALC may be a red herring.

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