In the 70s I used a QF-1 in conjunction with my Argo 509 and the optional outboard audio filter for the Argo, I found it to be very effective for QRP DXing and contesting. 73, Greg -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.11.14/127 - Release Date: 10/10/2005