I live at a very noisy QTH in central Seoul, Korea -- a city of over 12 million. Lots of lighting, wifi, broadcast radio, and whatnot, all around me. I currently own an ICOM 7300 and recently purchased a cheap little Yaesu FT-891. Low and behold, the FT-891 consistently beats my 7300 on receive, when I utilize the DSP noise reduction. This seems to go against all wisdom of tests, as I understand them (big point), about these two radios. Shouldn't the 7300 be blowing the 891 out of the water? Now, I must also say that I am employing every single known trick of the 7300 -- adjusting the Twin PBT in every way, adjusting the internal EQ, and setting the RX bandwidth filtering (which I must have mistaken equaled a bandpass filter, of sorts). and releasing the ALC to boost the snot out of the signal (at my QTH, overloaded with noise). I am even using the notch filter on voice signals, to some success.... I do know how to adjust every nuance of the 7300, and spend a lot of time tweaking. The 891 STILL beats it -- mostly because the 7300 seems to not handle the noise as well. I posted about this fact, and someone told me it may have something to do with the 891 having a 3khz roofing filter, and the 7300 not having one. I have very little understanding of roofing filters. My experience with a roofing filter started with a Yaesu FT-950 (which, by all accounts I've read, has a borderline useless set of roofing filters). The roofing filter on that rig only ever seemed to change the EQ of my rig, but didn't help the signal much. Perhaps this skewed my understanding of what the roofing filter can do? SO... What I'm curious about now... can I buy/add some kind of external filter, at the antenna, to help my Icom 7300 shine better? Something that will remove all of those extra noises that may be overloading my 7300's front end, so that I can take advantage of the sensitivity of this rig, in this noisy environment? Or maybe I should look into a better home rig with a solid roofing filter? Maybe I'm still not understanding what roofing filters do... please school me, because it's still a shaky concept, for me.