High-pass filter on IQ demodulator live audio out

Hi everyone,

SDRDharp author (@lambdaprog) recently included a new AM splatter and co-channel QRM canceller. I've got some really cool results using KiwiSDR IQ demodulator, saving the recording to a WAV file and opening it on SDR#.

Next, I tried routing the KiwiSDR live audio out to SDRSharp (used Virtual Audio Cable). But I've got something unexpected for a IQ stream. It seems there a high-pass filter in effect notching the range around 0 to 70Hz on both left and right channels This effectively kills the AM carrier required by the canceller algorithm.

I found Firefox may pass audio thru an HPF under certain codecs. VAC has a Channel Mixing option. I toggled off both neither removed the HPF.

I also tried visualizing the live IQ out on Audacity and, sure enough, the lower 60-70Hz are also heavily attenuated

I wonder if you all could point me if this a expected behaviour or something on my setup? If the latter, any suggestions where I should look into?


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