The amateur bands are filling up with very dirty data modes transmissions, we are seeing single PSK and JT65 transmissions taking out the entire modes’ sub-bands in some instances and this is entirely avoidable, not to mention completely unacceptable.
This video is an addendum to my previous video regarding the setting up PowerSDR for data-modes (digi-modes) because there are some settings in Windows which can significantly contribute to IMD on TX.
We take a walk-through of VAC’s (Virtual Audio Cable) Windows driver back-end which defaults settings to 44.1kHz potentially adding unwanted sample rate conversions which can introduce further IMD, then look at how to have Windows reduce audio drive, cleaning up the outgoing AFSK.
The motto of the video is, ensure your ALC compression is zero and that the ALC is in negative figures of between -0.5 to -1.0 dB (legacy radios = NO ALC deflection at all) to guarantee minimum IMD resulting from audio drive levels. Depending on the mode, you may want to drive at even lower levels.
Video Rating: 4 / 5