Review of Various Commercial Audio Filters With the widespread introduction and adoption of DSP filters . Autek QF-1A This is a different filter than the QF INSTRUCTIONS. QF-1A AUDIO FILTER Your new audio filter is the product of several years of development by the originator of commercial active audio filters. Second Hand Autek Research QF-1A SSB/CW/AM Audio Filter, It is an active AF filter (peak, notch, Low Pass) with variable frequency and selectivity. It works. Autek Research QF-1A product reviews by real people like you. Only at pethydro.org . - pethydro.org Description: SSB/CW/AM Audio & Notch Filter. Product is not in. Find many great new & used options and get the best deals for Autek Research QF-1A Active Audio Filter at the best online prices at eBay! Free shipping for. U Autek Research QF-1 $ SOLD Audio Filter This Autek Research QF-1 audio filter features: Peak, Notch and Low Pass. Input is via a hard wired ¼. Your Autek QF-1A audio filter is the product of several years of development by the originator of commercial active audio filters for shortwave communications. Download AUTEK QF-1A AUDIO FILTER. service manual & repair info for electronics experts. View and Download Autek Research QF-1A user manual online. Active Audio Filter. QF-1A Recording Equipment pdf manual download.