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Title: Wanted: Info on making higher Q notch filters Post by: WA2SQQ on December 14, 2020, 01:58:13 PM I’m doing some experimenting trying to build very sharp notch filters for the a.m. broadcast band. I’ve discovered that using larger value silver mica capacitors seems to improve the Q. I’m wondering if anyone has any data that shows the advantages or disadvantages using different gauges of wire? The first coil that I built I used some 24 gauge Kynar wire left over from the wire wrap days. I used a piece of PVC pipe as the coil form. I’m wondering if winding the coil on a ferrite rod might increase the Q. any suggestions would be appreciated
Title: Re: Wanted: Info on making higher Q notch filters Post by: WBear2GCR on December 14, 2020, 02:19:55 PM Afaik, the wire makes no difference in the BC band.
Series DCR and reactance matters, as does the inherent quality of the cap at the frequencies of interest. So, iirc ESR matters. I think the Q factor for coils may be improved with the use of ferrite cores... assuming proper selection. I'm weak in that area. But if you are trying to notch out one particular station, then multi-pole filters would be the way to go. Possibly a crystal filter might fly? Title: Re: Wanted: Info on making higher Q notch filters Post by: Opcom on December 15, 2020, 02:45:09 AM At BC frequencies, could a gyrator act as the inductance with high Q? AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
chapter 6 https://www.ti.com/lit/an/sboa093a/sboa093a.pdf http://tools.griffineffects.com/gyrator.php just a late night thought. |