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In Digi Modes ALC in Yellow?

W2ECK
W2ECK Member ✭✭
New user with question regarding ALC meter. Have noticed when getting Fldigi working that when transmitting the ALC meter is in the yellow.
- Is that OK as long as not in the red ?
- If not how does one adjust the audio drive level in digi modes in SSDR ?

73
Paul
w2eck

Answers

  • John - AI4FR
    John - AI4FR Member ✭✭
    edited July 2019
    Excellent questions. I keep mine out of the red at all times! Even the tiny slot/dash in the SDR ALC scale is out of the red. I adjust mine using DAX.
  • W2ECK
    W2ECK Member ✭✭
    edited March 2019
    I tried  the DAX Tx Gain adjustment and it seems like it was lowering the  Rf power out? 
    Paul
    w2eck
  • Neal Pollack, N6YFM
    Neal Pollack, N6YFM Member ✭✭
    edited December 2018
    That is correct, backing off the audio drive will lower output power, while also reducing distortion and splatter. 

    There are several points in the audio chain that can control TX audio level;

    1.  Windows PC audio output level:
         https://www.youtube.com/watch?v=ko1A1qcqWWQ
         at about 3 minutes into the video, how to set output level for a specific audio channel.

    2.  FLdigi Transmit Attenuator setting;
         Bottom of this page;  http://www.w1hkj.com/FldigiHelp/audio_adjust_page.html

    3.  If using WSJT-X for FT-8, the PWR output slider on the right hand side of the
         program user interface screen.

    Please understand that properly adjusted TX audio for a clean signal WILL result
    in reduction of transmit power level, but also will avoid distortion, clipping, and
    splatter across the radio band.

    NOTE:  Modes like JT65 and FT8 are not sensitive to small amount of ALC action,
                 but with phase sensitive modes like PSK, you should not let ANY ALC show
                 on the meter.   [I have done extensive lab testing with JT & FT8 modes using
                 a spectrum analyzer, as well as on the air coordinated testing, and moderate
                 ALC on the rig meter does nothing to JT or FT8 modes.  You can't say the same
                 for PSK modes, avoid ALC with PSK modes.]

    Cheers
  • W2ECK
    W2ECK Member ✭✭
    edited March 2019
    Neal and all
    thanks for the replies and help. Neal thanks for the results of you testing and the insights of ALC effects on PSK31 vs. the WSJT-X modes. I am coning from the elecraft K3 worked where you shot for 5 bars on the alc meter and if over you could adjust it down by using the mic gain knob and not have to touch the power knob. As I recall you could also adjust in the Windows Sound playback levels tab. But here we are using the DAX Tx gain adjustment.. 
    - but still am not clear whether in FT-8 by lowering Tx gain to bring the ALC down (and thus power out) I will get the same results?
    73
    Paul
    w2eck
  • Neal Pollack, N6YFM
    Neal Pollack, N6YFM Member ✭✭
    edited December 2018
    Hi Paul:

    Yes.   To affect your ALC meter setting (and audio gain/drive), you can adjust ANY  point in
    the audio output path between WSJT-X and the physical radio.  This includes the audio level
    slider on WSJT-X (right side of window), the MS Windows Audio Playback Level slider, the
    Flex DAX TX gain slider, all of them are effectively in series.  Any one, or all, will control your
    audio drive level.

    Cheers,

    Neal

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