Just finished the MARS mod on my IC-705 and noticed the TX audio seems a bit compressed compared to my other rigs. Has anyone experimented with the internal audio processing settings?

Also considering a simple low-pass filter mod on the 10W output to clean up harmonics. The stock filter seems adequate but I've seen some spurious content above 30MHz on my spectrum analyzer during FT8 operations. Anyone done similar work on the 705's final stage?

Running mostly digital modes (FT8/FT4) and would appreciate any insights on improving the overall signal quality while maintaining the factory power output specs.

I did the MARS mod on mine last year and noticed the same audio compression issue. Check menu item 3-19 (MIC GAIN) - factory default is too high for clean digital modes. I dropped mine to about 30% and the difference was night and day.

For the harmonics issue, I added a simple 7-pole Chebyshev filter after the antenna connector. Used silver-plated air core inductors and NPO caps - measured -50dB at 2nd harmonic. The 705's internal filter is decent but not contest-grade clean.

Be careful with the final stage mods - those SMD components are tiny and the thermal management is already pretty tight in that little radio. I'd suggest external filtering instead of internal modifications unless you have serious SMD rework experience.