Some things to consider:
- Install JP1 on the Quantar's RTCM. The squelch should calibrate at around 4 blinks rather than the 12 blinks or so without JP1.
- Be sure you've done the diode and squelch calibration with the actual attached radio (no antenna).
- The Quantar firmware should be 20.14.48 as later versions have better noise output.
- Try the "Chuck Squelch" RTCM version. They say it's better. I'm not sure I can tell the difference.
- Each RTCM should have 3 to 5 turns past threshold to prevent the squelch form being too loose. Somewhere around the 350 level seems about right. Chuck Squelch seems to need fewer turns but YMMV.
- Don't "and" CTCSS with squelch. That may override the RTCM's squelch detection. Compare with CTCSS on and off to see effect if any.
Hope this helps.