Thank Davolijj. The new antenna surprised me. Audio is clearer than ever. The audio path had changed a tad too: the compressor section was bypassed, and only the gates and peak limiter are active on the Alesis 3630. I also added a passive HPF at the PRO34 output, as well as a passive clipper and BPF just before the soundcard. The PRO34 output thumps were minimized, and unneccessary high frequencies are now attenuated. The clippers allow me to maintain a constant level at my soundcard input and avoid clipping in the A/D of the soundcard, and the BPF attenuates spurious high frequency components of the audio, both present in the audio as well as those created by the clippers in action.
The GP antenna allows reception of acfts. at SARI ground, as well as acfts. in SGES ground. I still don't know why I didn't use it before !
I am pretty happy with my gear now.