EMRFD Message Archive 2858

Message Date From Subject
2858 2009-04-03 14:12:48 Phil Sittner 30khz resolution filter-W7ZOI/K7TAU SA

I have a wonderfully functional SA thanks to alot of help from Wes but wish to add a 20-30khz resolution filter. One of the early updates referenced a design by W2EKB and WB4RNO using some filter modules from ECS yet I don't find these available at 10mhz-only 10.7mhz. Has anyone tried using individual 10mhz crystals to build a filter with this wide a bandwidth or would anyone have a recommendation as to how many poles and which design (Chebyshev, Butterworth etc.) as a starting point. My initial attempts have all resulted in narrow width performance.

Phil kd6rm

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2859 2009-04-03 14:32:19 Wes Hayward Re: 30khz resolution filter-W7ZOI/K7TAU SA
Hi Phil,

The 30 kHz bandwidth filters used in my analyzer, as well as the one that Terry White built both used crystal lattice filters. The crystals for such a filter would cost you more than it would to just shift your IF to 10.7 MHz. The 10.7 filters are readily available and the design details are all
2860 2009-04-03 14:50:32 Phil Sittner Re: 30khz resolution filter-W7ZOI/K7TAU SA

Thanks for the advice. I'll shop around some of the Silicon Valley surplus outlets for a crystal for the tracking generator. The 110.000mhz crystal I'm currently using came from there and I also picked up some 110.500 and 110.800 units. I'll also order some 10.7 lattice filters and let you know the outcome. Thanks again.

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