Hello David, Thank you for your response regarding the 1.5Khz INRAD filter. I agree, I would not buy the 1.5 if I had the 1.8 or 2.1 filter. Since I do not have a filter between 2.7 and .5, I am going to give the 1.5 serious consideration. Thanks again for your reply. Best 73, Roy Morris W4WFB