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Re: Spurs - BPF fix?

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Arv Evans All Messages By This Member #57044 Glen, Allison, Warren, Farhan, etc. After much tinkering with 15M band filters, it seems that the Elliptical or Cauer filter is easiest of the simpler filters to get an adequate dip at 23.55 MHz.? Blue line is input (1V, 0 DB) and green line is output at the load resistor.? What is thinking regarding the Elliptical or Cauer filter?? I don't think I have ever used one.? The tuning is difficult, especially placing the trap frequency.? C3 (59 pf) might have to be a trimmer so that it can be set exactly on the 23.55 MHz spur frequency.? R2 widens the notch bandwidth but also decreases the amount of attenuation at 23.55 MHz.? With a trimmer at C3 to precisely adjust the notch frequency it might be possible to eliminate R2 which would change the notch attenuation to 50+ DB. This is fun, but admittedly I have probably exceeded my level of incompetence here.? 8-) Arv _._ toggle quoted message Show quoted text On Sun, Aug 12, 2018 at 3:28 AM Glenn <glennp@...> wrote: Allison, yes we are on same page. See summary in picture below. Hopefully correct and less my typos in previous post. The 15M band is odd one out though for switching. Yes, i know anything? is possible.?? But there are at least 3 or 4 variations on the uBITX Sketch so an agreement has to come on how to do this and also make it not so difficult that people can't be bothered to make the changes. Of course in the end, we can't push people to do this if they don't want to, but we do have to make it as easy as possible in my view. There have been hundreds on this and similar topic, but it's like a Committee where nothing changes so far. Cauer_Elleptical_Filter_dip_at_23.5_MHz.asc Cauer_Elleptical_Filter_dip_at_23.5_MHz.asc LTspice IV - Cauer_Elleptical_Filter_15M_dip_at_23.5_MHz.png Cauer_Elleptical_Filter_dip_at_23.5_MHz(expanded_MHz-scale).png

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#57044

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