When you say "I get distorted audio", how do you know this? If you are listening with MON, it will sound distorted to you because you are hearing the raw DAC data and when PS is enabled that DAC data is, of course, pre-distorted!
Or is somebody reporting this to you on the air?
What ANAN, what amp, and what coupler/sampler are you using?
It seems like you are badly overdriving your amp. 106W out of the ANAN into the amp? And look at how badly the blue line is going horizontal up at the top right corner of the AmpView display. Back the drive off some.
I'm going to guess that you are using the metering on your amp to make adjustments, which is perfectly reasonable, of course.
But a lot of amp metering does not respond correctly when using two tone, and this can fool you badly. I have this exact problem with my Elecraft KPA1500. One way to fix this is to change your two tone settings from the standard 700 and 1900Hz to 70 and 190Hz. While this is not the "official", de facto standard for measuring IMD, it nevertheless works extremely well for making amp's and metering behave, and it works perfectly fine for obtaining a PureSignal correction and getting a good idea of what your IMD is. It also has another benefit, which is that it does not "sing the song of our people" on the air
Other things to consider after changing the tone pair and reducing drive:
- Set your TX DUP display scaling to be 0 to -70dBm, this will net you a much better view of your transmitted signal and anything under -70 is a "don't care".
- Uncheck Low Res on the AmpView display.
- Enable Quick Attenuate Response.
- Try disabling MAP and enabling STBL.
Examples of improper and proper behavior of amp metering at my station are shown below. Right click and "Open image in new tab" for full resolution.
The first image shows how my KPA1500 responds using the 70 & 190Hz non-standard two tone configuration. As can be seen, the (calibrated) drive is 35 and the KPA1500 is reporting 37W in (close enough) and 1585W output (this is into a dummy load). Note the Thetis power output of 45W (uncalibrated). The AmpView display shows a nice, smooth curve with very little leveling off up at the top. IMD is better than -50dBc.
The second image shows how my KPA1500 responds using the 700 & 1900Hz standard two tone configuration. Again the calibrated drive is 35 but the KPA1500 is only reporting 21W in and 1261W out. Meanwhile the uncalibrated Thetis power meter still shows the same as in the previous case, 44W (close enough), i.e. it is unaffected by the tone pair selection. The AmpView curve remains identical, albeit with the characteristic dotted line you get with the standard tone pair which is normal.
In both cases I'm confident that the actual power output of the amp is 1500+W.
Try changing to 70 & 190 and turn that drive down!
- 70&190.JPG (923.27 KiB) Viewed 6710 times
- 700&1900.JPG (925.64 KiB) Viewed 6710 times