I need a 221 filter and have a 218 to trade or cash. The 221 is the 250hz centered on 500hz and the 218 is the 1.8khz narrow ssb filter both for 9 mhz. It will work on any TT rig with a 9 mhz IF. If I can't find a 221 then I might consider a 219. PayPal user Steve N4LQ