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Friday @ 12:30 PM   

Field Day Filters for Same-Band CW/Phone Interference
Nelson Sollenberger (KA2C )
Interference between phone and CW operations for Field Day on the same HF band is a common problem, even with high performance rigs and careful antenna design and layout. Ultra Sharp filters are possible which can effectively separate CW and phone segments on the HF bands with 50 to 100 KHz separation between signals. Two types of filters will be detailed in this presentation: 1) Ultra-Sharp Low-Loss filters suitable for usage both during TX and RX; and 2) Ultra-Sharp RX filters suitable for RX usage that are bypassed during TX. These filters combined with other techniques have been effectively used by W3CWC (Antietam Radio Association of Hagerstown, MD) to eliminate Field Day interference problems when operating on the same HF band with phone and CW. Multi-stage notch filters combined with bandpass bump configurations using very-high Q helical resonators or very-high Q lumped element filter designs are used in the Ultra-Sharp Low-Loss filters, and high Q toroid inductors are used in the Ultra-Sharp RX filters. Operating on Field Day without phone/CW interference is a pleasure.
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