At first I was annoyed because it wouldn't accept composite sync for its sync signal. I had to sit there for a while trying to figure out what was wrong with it as the ebay listing clearly advertises that it loves the sega genesis. Then I remembered that scart uses composite video for sync and not composite sync so I fed it composite video and BAM, got a picture, and could CLEARLY see all the interference. My component tv looks muddy with component usually even the component video from the modern video card in my computer doesn't look good on that tv....but this encoder I bought looks pixel perfect it's so sharp I didn't expect this at all. So once I got the darn thing working (I wired it up myself no need for a scart cable) I must say this's the best rgb to component encoder I've found yet!
Also I agree it would be interesting to see if the subcarrier messes up the 6592. But I mean if bringing the subcarrier close to the cxa1145 without touching the chip or its pins made the interference worse....not sure how much of a difference that would even make. The subcarrier seems to just be oozing the interference I honestly didn't think that would be possible. Learn something new everyday.
Also to weaken the subcarrier you'd use a resistor. The genesis built in circuit already has the subcarrier pass through a 10k ohm resistor which is already a fairly strong resistor. Weakening the subcarrier probably won't do a thing it's just a garbage signal. Honestly...f#ck the subcarrier I never want to use that thing ever again! The subcarrier is obviously the source of all video quality evilness inside the genesis haha. I'm willing to bet master systems with the same sort of interference are suffering the same problem. Weakening the messed up signal won't change it it'll still be messed up and it's driving the colour encoding which is why we get jailbars AND rainbow banding.