Hi David I use a 250 cycle filter in my TS-450 and it works great for RTTY. 73 Tom W7WHY Hello everyoneI would like to outfit my FT-857D portable rig with an IF filter on its 455khz stage. INRAD sells a suitable 500hz unit. They also have a 300hz unit. I am leery about the 300hz filter being too narrow. Any opinions? 73Davidhttp