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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

The annual “Alexanderson Day” transmission from the World Heritage Grimeton site in Sweden, using the vintage Alexanderson alternator on 17.2 kHz will take place Sunday, June 29 at 0900 UTC (SAQ will start tuning at about 0830 UTC) and again at 1200 UTC (SAQ will start tuning at about 1130 UTC). An SAQ transmission will take place on July 2 at 1430 UTC (SAQ will start tuning at about 1400 UTC, …

American Radio Relay League | Ham Radio Association and Resources

The Voice of America Radiogram show, hosted by Kim Andrew Elliot, KD9XB, will be testing a variety of digital modes on March 16 and 17.

The data transmissions can be decoded by anyone with an AM shortwave receiver using any of the popular sound-card-based programs such as Fldigi, Ham Radio Deluxe, MixW, MultiPSK, DigiPan (for BPSK31, BPSK63 and QPSK31 only), CocoaModem (for Macs) and others.

Eac…

American Radio Relay League | Ham Radio Association and Resources