Ten Tec crystal filters #288 (1.8khz) and #285 (500hz) fits Corsair, Paragon, Omni V, Omni VI (perhaps others with 6.3MHz IF)and the #285 fits the 580 Delta. $75 each shipped to you in USA, or trade both for a 283 VFO for the 580 Delta. If interested please email me off the list at: r-mason at cox.net Thanks Roger N4HSI