Worse modulation with my setup

  • Hi,
    i am using Adalm Pluto over LAN. RF Side works perfect with SG-Labs Amp on a 5 turn Helical, but i have
    problems with my modulation. I am using a Headphone/Mic from Heil on the (normally fine) built-in Soundcard
    on my Desktop-PC. Level ist very low from mic, so i used +30dB preamp setting in Soundcard and have to level up more than 90% of Mic level at SDR Console to get a reliable SSB signal, but Modulations is absolutely worse.
    If i use the SDR Consoles internal test Tone, all looks ok. I have clean spectrum on RF with double tones wich are generated within SDR Console, (measured after PA with my HP Scpec, so i think the problem must be in Audio/Sound
    (or between my ears ;-)
    Also i got hi freq. audio distortions wich are not noticable if i monitor the audio via the soundcard itself.
    Any ideas?

    What type of audio interfaces / microphones are mostly used here i the community?

    Thanks in advance!

    BTW: all mods on Pluto done, & pwr supplys are clean and no RF strays in power lines / Mic / Reference freq. cables measurable....

  • Hallo,

    it is strongly recommend to use an external soundcard, especially in case of laptops. Some internal systems are not separated in input and output clearly. A simple external USB-Card will help. Probably the internal system must be deactivated completely.
    First, look at the Win-Setup. Check all the settings in the sound system carefully. If there is an AGC, don't activate it. If you find a level control slider in the sound system adjust it in a way that the VOX GAIN slider in the Console doesn't show overdrive. The VOX Gain slider shows the audio level input to the Console given from Windows. All this must work correct, the audio spectrum in the transmit window shows it without transmitting also. If there is less audio level given from Win to the Console something is wrong. At the lower right side in the transmit window there is a audio monitor. Some time ago, there was a recommendation to install a virtual audio cable to avoid distortions when using this monitor. Don't know why but it worked.
    If all this is running, use the equalizer to adjust more gain at higher audio frequencies and turn the compression on. Audio gain sliders shoud be at 50, compression at 30 for example. Set the booster to 5dB. If you need more, search the reason for it.
    At least it will be a very clear signal with high linearity and good frequency response. The RF Gain slider should not exceed 90. Don't hesitate to ask for more help.

  • Hallo all..

    i had the same problem in past with low modulation level using a simple SKYPE USB HEADSET with an Soundcard inside.

    The max. Digital Gain in SDR Console is a bit to low....

    so i tried

    EQUALIZER APO to add a bit of MIC GAIN to the mic in the headset and maybe to use some additional EQUALIZER


    Not easy to configure and install and had also some trouble with other soundevices at first , but i got it working

    73 de dg0opk